Rear end acted up after manuallel putting car into 4 wheel drive.

[Eagle1984]

Today after getting my Eagle back from the shop to get its 4 wheel drive manually engaged. At first it was fine and did about 60 down the road but later tonight when I went to leave for college about after 15 minutes of driving and getting gas something went wrong with the rear end. It sounded almost as if the engine was over revving and there was a weird almost squick/scrapping sound almost as if something was not engaged all the way. The odd thing is that the sound was coming from the rear axle. When I tried to put it into gear a few times after shutting it off it still made the noise and when I put it into drive it would not move, even the front axle was not moving which I found odd as it should have been in 4 wheel drive. Was this just the 4 wheel drive messing up or is it something worse like my rear end.

[AMC of Houston]

Maybe the dreaded Eagle right rear axle fracture??

[eaglefreek]

It sounds like it popped out of 4wd and is between 2 and 4wd.

[Eagle1984]

It sounds like it popped out of 4wd and is between 2 and 4wd.

Thanks that is what I am hoping it is. Hopefully not the axle fracture thing. What is the best way to put it into 4 wheel drive manual that is guaranteed to stay that way, is there a way to make it permanent. Will running it to long this way cause damage cause my dad did listened to it for a few minutes while he told me to add some gas while in drive. Also why would the noise be coming from the rear axle and not the front.

[carnuck]

If it's 1/2 way, hopefully you didn't wipe out the viscous coupler.

[Eagle1984]

If it's 1/2 way, hopefully you didn't wipe out the viscous coupler.

what would happen if I did wipe out the viscous coupler?

[Eagle1984]

Also just wondering but what would happen if I replaced my Transfer case with a 119 which only has 4 wheel drive? Can it be done on a 1984 Eagle.

[carnuck]

It wouldn't go anywhere and yes, a NP119 will fit as long as the front axle didn't disengage you'd be okay.

[Eagle1984]

It wouldn't go anywhere and yes, a NP119 will fit as long as the front axle didn't disengage you'd be okay.

Thanks, how would I engage the front axle. Is it a hard or expansive thing to engage the front axle and install the 119? It seems with the 4 wheel drive system that would be the easiest compared to switching it into 4 wheel drive manually and hoping it stays there. How would you permanently switch a 1984 Eagle into 4 wheel drive? Permanently. And engage/lock the front axle on a 1984?

[carnuck]

If the tcase was put into 4x4 and teh front axle wasn't. the tcase is likely dead. The viscous coupler needs BOTH axles engaged to work properly or it slips till it self destructs!

[Eagle1984]

If the tcase was put into 4x4 and teh front axle wasn't. the tcase is likely dead. The viscous coupler needs BOTH axles engaged to work properly or it slips till it self destructs!

Would the car still drive fine until it self destructs, because it seemed to run fine until this happened. Do all model year eagles require that or did they ever change it? When the T-case is manually changed to 4 wheel drive is the Front axle locked automatically?

[Eagle1984]

I will have to ask my mechanic to see what he did, supposedly he has done this before. He said when I picked it up that he checked and the front tires were defiantly gripping as he put it(tried it out on some gravel) and I did noticed a difference in the way it felt and handled.

[carnuck]

If the front axle is vacuum, sometimes they don't stay engaged (almost all '82 to '86s with NP129. NP128s went back to non-vac for '86 then NP129 came back till the end of production)

[Eagle1984]

If the front axle is vacuum, sometimes they don't stay engaged (almost all '82 to '86s with NP129. NP128s went back to non-vac for '86 then NP129 came back till the end of production)

Thanks, that is probably what it did. Is there a guraunteed way to keep the front axle engaged. My mechanic did mention the houses going to the front axle.

[mudkicker715]

Look in the eaglepedia.

[Eagle1984]

Look in the eaglepedia.

I checked the eaglepedia and only seemed to find information about the transfer case, nothing about the front axle using vac hoses.

[jim]

Somewhere there is an explanation about locking in the front axle with a hose clamp.  It's a simple job but can be messy because you have to pull the cover off a small box and let the gear oil run out - sometimes down your arm.
The shift motor on the transfer case can be tied into place with wire.  I ran my 83 that way all last winter and just cut the wire and put it into 2 wheel drive in the spring.  It had jumped into false neutral the winter before and almost stranded me a few miles from home.
It does not hurt an Eagle to run in 4 wheel drive all the time.

[Eagle1984]

Somewhere there is an explanation about locking in the front axle with a hose clamp.  It's a simple job but can be messy because you have to pull the cover off a small box and let the gear oil run out - sometimes down your arm.
The shift motor on the transfer case can be tied into place with wire.  I ran my 83 that way all last winter and just cut the wire and put it into 2 wheel drive in the spring.  It had jumped into false neutral the winter before and almost stranded me a few miles from home.
It does not hurt an Eagle to run in 4 wheel drive all the time.

Thanks, I will have to let my mechanic know as I believe right now he is just trying to find a way of having the switch on the motor for the front axle stay in place, though this seems easier.

[mudkicker715]

Look in the eaglepedia.

I checked the eaglepedia and only seemed to find information about the transfer case, nothing about the front axle using vac hoses.

http://www.amceaglenest.com/~iowaeagl/guide/index.php?title=Front_Axle_Lock

[Eagle1984]

Somewhere there is an explanation about locking in the front axle with a hose clamp.  It's a simple job but can be messy because you have to pull the cover off a small box and let the gear oil run out - sometimes down your arm.
The shift motor on the transfer case can be tied into place with wire.  I ran my 83 that way all last winter and just cut the wire and put it into 2 wheel drive in the spring.  It had jumped into false neutral the winter before and almost stranded me a few miles from home.
It does not hurt an Eagle to run in 4 wheel drive all the time.

what does the shift motor look like and how did you tie it in place. Sorry about all the question just want to be as detailed as possible for when I tell my mechanic.

[Eagle1984]

Thanks for all the responses. Well my mechanic work on it and it seems the lever on the transfer case had simple come loose. Might still have my mechanic lock the front axle in the way you guys have shown though he seems confident in the way he did it and I do not want to offend him. Something about him working 30 years on cars and knowing what he is doing, or so my parents say.

[eaglefreek]

Not discounting your mechanic's actions, there are a few ways you can lock front axle but my dad got thrown out of an auto repair shop years ago because the mechanic said, "I've been doing this 30 years!" My dad said, "Just because you've been doing something for 30 years, doesn't mean you've been doing right for 30 years."

[mudkicker715]

since it failed once he sounds like a vet mechanic that needs all the help he can get.

If he is not so arrogant than he would accept it.

[Eagle1984]

since it failed once he sounds like a vet mechanic that needs all the help he can get.

If he is not so arrogant than he would accept it.

I do not think my mechanic would be the problem it would be my dad. He seems to think he is right about everything and hates it when people doubt his vehicle knowledge, plus my parents are helping with the repair bills.

[thereverendbill]

Also just wondering but what would happen if I replaced my Transfer case with a 119 which only has 4 wheel drive? Can it be done on a 1984 Eagle.

I recently did this swap in my 1983.  you have to make sure that the front axle is locked in 4wd or the car will not move at all and just spin the front drive shaft.

You have to make sure that you get the correct speedo gear for the 119 cause it is bigger (physically) than the one in your current unit.
Your speedo will be in accurate after the swap.  mine says it's doing 20 when the car is actually going 25 and says i am going 57 when the car is actually going 65.

 

[eaglefreek]

Also just wondering but what would happen if I replaced my Transfer case with a 119 which only has 4 wheel drive? Can it be done on a 1984 Eagle.

I recently did this swap in my 1983.  you have to make sure that the front axle is locked in 4wd or the car will not move at all and just spin the front drive shaft.

You have to make sure that you get the correct speedo gear for the 119 cause it is bigger (physically) than the one in your current unit.
Your speedo will be in accurate after the swap.  mine says it's doing 20 when the car is actually going 25 and says i am going 57 when the car is actually going 65.

 

Could it be because the car the 119 came out of had a different axle ratio than yours?

[Eagle1984]

Also just wondering but what would happen if I replaced my Transfer case with a 119 which only has 4 wheel drive? Can it be done on a 1984 Eagle.

I recently did this swap in my 1983.  you have to make sure that the front axle is locked in 4wd or the car will not move at all and just spin the front drive shaft.

You have to make sure that you get the correct speedo gear for the 119 cause it is bigger (physically) than the one in your current unit.
Your speedo will be in accurate after the swap.  mine says it's doing 20 when the car is actually going 25 and says i am going 57 when the car is actually going 65.

 

Were did you find one. Around where I live even ones in Junk yards are a rare site. Drove 6 hours just to get mine. Do they come up for sale on this site often? Looks like I will not be able to get the Eagle back in to lock the front axle the way shown here until thanksgiving. Then again he said he has done it before and so far it is working well.

[eaglefreek]

What is your reason for wanting a 119? Changing out a transfer case is a lot more work than getting the transfer case shifter mechanism working. If you really want one, I may know of one in the Denver, CO area from my old 81 Eagle that had 85k miles on it. 

[Eagle1984]

What is your reason for wanting a 119? Changing out a transfer case is a lot more work than getting the transfer case shifter mechanism working. If you really want one, I may know of one in the Denver, CO area from my old 81 Eagle that had 85k miles on it.  

I would just repair the vacuum system but can't seem to find a diagram for my model year. Will have to see what the gas millage will be like but I kind of like the idea of having it in 4 wheel drive all time, plus with a 119 one less then to worry about going out of 4 wheel drive, then all I have to worry about is the front axle. I thought having the 2 wheel drive option sounded nice but is the game millage really that much worse with 4 wheel drive? I guess you could say I live the better safe then sorry motto. Worry about small things and what could happen.

[carnuck]

The diagram I gave my buddy should still be up on http://oljeep.com The Jeep diagrams for the GW are almost identical for your setup. Jeep made it way more complicated than it needed to be. By '86 they fixed that by doing away with the vacuum front axle (like they were originally in '80/81 except 2wd was still possible)

Best setup: Vacuum from motor to reservoir. From reservoir to switch. 2 lines on switch (2wd and 4x4) Flip switch and vacuum goes to tcase vacuum motor, pulling it into 4x4. (this is with a locked or non-vacuum front diff) Flipping switch other way moves tcase vacuum motor to 2wd position. Best part? It is now shift on the fly!

[Eagle1984]

The diagram I gave my buddy should still be up on http://oljeep.com The Jeep diagrams for the GW are almost identical for your setup. Jeep made it way more complicated than it needed to be. By '86 they fixed that by doing away with the vacuum front axle (like they were originally in '80/81 except 2wd was still possible)

Best setup: Vacuum from motor to reservoir. From reservoir to switch. 2 lines on switch (2wd and 4x4) Flip switch and vacuum goes to tcase vacuum motor, pulling it into 4x4. (this is with a locked or non-vacuum front diff) Flipping switch other way moves tcase vacuum motor to 2wd position. Best part? It is now shift on the fly!

Thanks, as for the best set up I am not sure what you mean, do you have a diagram of it. Would not mind trying that. The one on the site I need is the 1983/1984 vacuum front axle and vacuum system diagram right. Been driving her again and was wondering when I but her in gear there is a rumbling noise that come from the car but only in 4 wheel drive, also I only hear it when I am sitting still or waiting to make a turn, if I am moving I do not hear it as much. The engine runs fine but the car sounds different. Is that how it is supposed to sound in 4 wheel Drive? Sorry for the questions just be cautious as this is the first Eagle I have owned so not sure what is normal.

[carnuck]

Have you checked the diff and tcase oils? Best set up is permalocked front diff and vacuum to/from shifter motor on trans only (same as '86 to '88)

[Eagle1984]

Have you checked the diff and tcase oils? Best set up is permalocked front diff and vacuum to/from shifter motor on trans only (same as '86 to '88)

I should also mention that the car seems to vibrate too, when it is rumbling. Is there a dipstick for the diff and tcase oils in the engine compartment like for the engine oil or are they on the parts themselves?

[mudkicker715]

Inspection covers midway up. I doubt that is it. Check for driveline looseness.

[Eagle1984]

Inspection covers midway up. I doubt that is it. Check for driveline looseness.

What do you mean exactly by Driveline looseness. How would I check for it.

[BenM]

Put the car up on 4 jacks, put the transmission in neutral. Spin all the wheels one at a time, see if one is significantly tighter then the others or makes noise. The front should drag more then the back, but not by a lot. If both back wheels make the differential click, then it may be the spider gears.

Also go under and turn the driveshafts. You will get a small amount of rotational play, but if the driveshaft clicks or grabs unevenly, or feels loose then you have a bad universal joint.

The transfer case has two big hex nuts on it, I usually use a crescent wrench on them, they should NOT be tighter then that, they're fill and drain plugs with washers into aluminum. Don't ape them on when you're done. You'll have to remove the skid plate.

You should be able to put your finger in the top plug and feel oil within 1/4" of the top, if not add some. Either get an assistant and a long hose or a hand pump to fill it, there's no room to tilt a bottle under there. Dextron is spec'ed for it, it's about 5w-20 equivalent motor oil. Early transfer cases spec'ed 10w30, but it was too thick and caused problems.

A vibration is probably between the transfer case and the road unless your transmission mount is shot, but it's a good idea to check the fluids while you're down there. You may want to check the differentials while you're under the car, they should be filled to the same standard, just under the bottom of the filler plug, with 75w-90 GL-5.

[Eagle1984]

Put the car up on 4 jacks, put the transmission in neutral. Spin all the wheels one at a time, see if one is significantly tighter then the others or makes noise. The front should drag more then the back, but not by a lot. If both back wheels make the differential click, then it may be the spider gears.

Also go under and turn the driveshafts. You will get a small amount of rotational play, but if the driveshaft clicks or grabs unevenly, or feels loose then you have a bad universal joint.

The transfer case has two big hex nuts on it, I usually use a crescent wrench on them, they should NOT be tighter then that, they're fill and drain plugs with washers into aluminum. Don't ape them on when you're done. You'll have to remove the skid plate.

You should be able to put your finger in the top plug and feel oil within 1/4" of the top, if not add some. Either get an assistant and a long hose or a hand pump to fill it, there's no room to tilt a bottle under there. Dextron is spec'ed for it, it's about 5w-20 equivalent motor oil. Early transfer cases spec'ed 10w30, but it was too thick and caused problems.

A vibration is probably between the transfer case and the road unless your transmission mount is shot, but it's a good idea to check the fluids while you're down there. You may want to check the differentials while you're under the car, they should be filled to the same standard, just under the bottom of the filler plug, with 75w-90 GL-5.

Thanks, so is a vibration normal? What would happen if I continue to drive it this way? Now I seem to be hearing a slight squeaking noise coming from the engine compartment but also only when I am in gear and stopped at a stop light, like the vibrating.

[GRONK]

You don't have mismatched tires do you?

[Eagle1984]

You don't have mismatched tires do you?

I will have to go to check that. I know the left rear passenger leaf spring is shot but I doubt that would cause a problem.

[Hawk258]

I have a silly question, but have you tried just swapping to a cable style activation system? At least then you would have a way of testing the system and having a slightly more relible system in the future.

[captspillane]

What you are experiencing is completely normal. I used to keep a 9/16 wrench in the glove compartment of all my Eagles for this reason. It was actually pretty silly of you to bring your car to a mechanic each time. I have had to crawl under my car at least a dozen times to reach up, put the 9/16 wrench on the transfer case lever, and push it back into the engaged position. When it happens the car revs up, acts likes it wants to move but can't, and then doesn't move. I eventually ripped the vacuum diaphragm out of the way and used rope to pull a slight tension against the hole the linkage used to connect to. It stays in just fine with just a little bit of pressure.

Do not overreact to people saying that you could have burned out a viscous coupling. Fact is that everyone is running burned out viscous couplings. They only last a few years and are designed to be changed out as often as you change clutchs, about 60K miles. It doesn't really do much and there really isn't much difference between the Eagle transfer cases that had them and the ones that didn't. Once it stops working you have an open differential between the front and rear yokes, which is why you have to keep the front from spinning freely if you want the back output to push you forward.

If you switch transfer cases, make sure to get a Cherokee low range unit. The select-trac designation means that it has an open differential or viscous coupling and the command-trac NP231 has a closed differential. All have the low range locked into a closed differential. Even if you run a 231 with the front and rear outputs locked together, you will not notice any major wear because the open differentials in the front and rear willl take up the slack. Its recommended to stick with the viscous coupling because in a Cheroke the front U joints will make a severe vibration at higway speeds if you're locked into four wheel drive. The CV shafts and independent front suspsnsion on an Eagle doesn't suffer those woes.

Don't hesitate to keep your Eagle in 4WD. It was designed to be all wheel drive before customers knew what all wheel drive was. There is no appreciable difference in gas mileage and its not worth the hassle to fix the vacuum switches. Just lock them in 4 WD and go on your merry way.

[Eagle1984]

What you are experiencing is completely normal. I used to keep a 9/16 wrench in the glove compartment of all my Eagles for this reason. It was actually pretty silly of you to bring your car to a mechanic each time. I have had to crawl under my car at least a dozen times to reach up, put the 9/16 wrench on the transfer case lever, and push it back into the engaged position. When it happens the car revs up, acts likes it wants to move but can't, and then doesn't move. I eventually ripped the vacuum diaphragm out of the way and used rope to pull a slight tension against the hole the linkage used to connect to. It stays in just fine with just a little bit of pressure.

Do not overreact to people saying that you could have burned out a viscous coupling. Fact is that everyone is running burned out viscous couplings. They only last a few years and are designed to be changed out as often as you change clutchs, about 60K miles. It doesn't really do much and there really isn't much difference between the Eagle transfer cases that had them and the ones that didn't. Once it stops working you have an open differential between the front and rear yokes, which is why you have to keep the front from spinning freely if you want the back output to push you forward.

If you switch transfer cases, make sure to get a Cherokee low range unit. The select-trac designation means that it has an open differential or viscous coupling and the command-trac NP231 has a closed differential. All have the low range locked into a closed differential. Even if you run a 231 with the front and rear outputs locked together, you will not notice any major wear because the open differentials in the front and rear willl take up the slack. Its recommended to stick with the viscous coupling because in a Cheroke the front U joints will make a severe vibration at higway speeds if you're locked into four wheel drive. The CV shafts and independent front suspsnsion on an Eagle doesn't suffer those woes.

Don't hesitate to keep your Eagle in 4WD. It was designed to be all wheel drive before customers knew what all wheel drive was. There is no appreciable difference in gas mileage and its not worth the hassle to fix the vacuum switches. Just lock them in 4 WD and go on your merry way.

So basically you are saying I should forget about repairing the vacuum system because it is a pain, which is how I feel and just put a piece of wire the form the switch to the lever on the transfer case and tie it in the engaged position, what is the best way to brace the lever to keep it engaged. Also I think I will keep it in 4 wheel drive, seeing as the mechanic charged $130 to change it the first time. Though I might have asked this already if I put in the 119 and the front does disengage will it cause any damage? and the vibrating is normal? sorry for all the question put this is the first car I have ever really tried to work on not really good mechanistically yet. Also with the cable through the floor how do you keep water from getting in where the hole is? also what do you mean exactly by  "Once it stops working you have an open differential between the front and rear yokes, which is why you have to keep the front from spinning freely if you want the back output to push you forward."

[captspillane]

Vibrating and wierd noises is a normal part of owning a 25 year old car, but they should always be looked at. Ideally there would never be any and some are harmless and others are not. It took at least three years of active witch-hunting to be able to drive my red SX4 without any squeaks or clunks. Good luck.

If you are under the car, you can look up on the drivers side of the car and see the front driveshaft attached to the yoke on the transfer case. Between the driveshaft and the side of the transmission is the vacuum diaphragm. Its round plastic with a metal rod sticking out of it. That rod is in an L shape, with the short part of the L poking through a flat piece of metal about three inches long. On the opposite end of that short piece of metal is a nut that accepts a 9/16 wrench. You put your wrench on that nut and twist it clockwise. The three inch piece of metal will rotate rearward toward the transfer case. It will noticeably click into place. Sometimes you need to reach up with your other hand and jiggle the driveshaft to get it to line up and click. That's what your mechanic did at a cost of over a hundred dollars. At the top of the three inch lever you can pop the rod out of place or just tie to the rod with rope, and then tie the other end of the rope to anything rearward of the lever. You do not need to drill anything or to put any holes in the floor. All the old vacuum lines can be removed if you plug them from leaking and ruining your idle. The shift switch on your dash will just be decorational. I am pretty sure it was clockwise for 4WD, but it may have been counterclockwise. I'm not home to double check.

[Eagle1984]

Vibrating and wierd noises is a normal part of owning a 25 year old car, but they should always be looked at. There should never be any and some are harmless and others are not.

If you are under the car, you can look up on the drivers side of the car and see the front driveshaft attached to the yoke on the transfer case. Between the driveshaft and the side of the transmission is the vacuum diaphragm. Its round plastic with a metal rod sticking out of it. That rod is in an L shape, with the short part of the L poking through a flat piece of metal about three inches long. On the opposite end of that short piece of metal is a nut that accepts a 9/16 wrench. You put your wrench on that nut and twist it clockwise. The three inch piece of metal will rotate rearward toward the transfer case. It will noticeably click into place. Sometimes you need to reach up with your other hand and jiggle the driveshaft to get it to line up and click. At the top of the three inch lever you can pop the rod out of place or just tie to the rod with rope, and then tie the other end of the rope to anything rearward of the lever. You do not need to drill anything or to put any holes in the floor. All the old vacuum lines can be removed if you plug them from leaking and ruining your idle. The shift switch on your dash will just be decorational. I am pretty sure it was clockwise for 4WD, but it may have been counterclockwise. I'm not home to double check.

Thanks, I never knew the clutch is supposed to be changed ever 60 thousand miles. Also how long could I put off the vibrating. I am currently in college and my usual mechanic is a 1.5 hour plus drive. Laverne is my daily driver.

[captspillane]

To explain my statement, let me explain what an open differential is. Imagine an axle sitting on the ground with no driveshaft or tires attached to it. If you twist the driveshaft yoke while holding one hub still, the other hub will spin. If you hold the driveshaft yoke still while spinning one hub, the other hub will spin in the opposite direction. If any one input or output is spinning, another input or output must also spin, but the third input or output can stay perfectly still. In your transfer case you have an input shaft coming from the transmission, an output shaft going to the rear driveshaft, and an output going to the front driveshaft. If you spin the input shaft and hold one output still, the other output must spin. If you hold the input shaft still, like when the transmission is in park, then the rear wheels can only spin forward if the front wheels spin backwards. So if you put the transmission in gear and apply engine torque to make the transmission output shaft spin, then the input shaft of the transfer case will spin, and one of the output shafts must also spin but the other output shaft has the option of sitting still. When your front wheels are no longer connected to the front driveshaft because of the front axle disconnect, the front driveshaft spins effortlessly while the rear driveshaft can only spin if the car moves forward. Your car won't move anywhere because the engine torque took the path of least resistance. In the same way your car will not move in 2wd if one rear tire is up in the air. The tire on the ground takes effort to spin, so it stays still while the other tire spins with the rear driveshaft. It does not damage anything if the front disconnects when you don't want it to, but the car might not move anymore.

In low range or with a "command-trac" transfer case, the differential is closed or locked. That means that if the rear driveshaft spins, the front driveshaft must also spin. It also means that if the input shaft spins, both outputs must spin together too. It wouldn't matter if the front driveshaft was removed or disconnected from the front wheels with a closed differential.

[captspillane]

A viscous coupling is like two hands interlaced. If you kept one hand still and your fingers spread apart, the other hand could move forward and backward with each moving finger passing between two stationary fingers. Inside the coupling are strips of metal connected to one output that pass in close proximity to strips of metal connected to the other output. The strips pass each other without touching, but there is a viscous fluid surrounding them. That means that if you spin one output really fast and let the other go slack, the viscous fluid will not be able to easily push out of the way. The slack output will naturally feel like spinning along with the moving output. You can always stop the slack output if you hold it still since its not rigidly connected to the spinning output, but the viscous fluid lets some degree of torque be transfered from the spinning one to the stationary one. When the viscous coupling wears out, which all of our antique transfer cases are, then there is nothing connecting the front driveshaft and rear driveshaft like any other open differential transfer case. When the viscous coupling is new, you can grab one driveshaft yoke and hold it still while slowly spinning the other driveshaft yoke, but you will feel the stationary driveshaft wanting to spin unless you exert alot of pressure.

[captspillane]

A clutch can last anywhere from 60K to 200K miles, depending on driving habits. The key to long life on a clutch is fast shifting. Thats counter-intuitive. The gripping surface on the clutch lasts forever if its cold. It sheds off material considerably faster when its warm, and insanely fast when its hot. In an exaggerated sense, the rate of wear is exponentially related to the temperature of the material. If you pull your clutch pedal back very slowly the car will smoothly start rolling. If you let the clutch out very fast, the car will jerk and toss your head around and the engine will probably stall. The smooth start requires the clutch to come into contact with the flywheel and slide against the surface, which heats it up quickly while the jerking start requires the clutch plate to contact the flywheel and almost instantly mate to it and begin spinning together without any sliding or any heat buildup.

In stop and go city traffic your clutch will heat up from many consecutive shifts. It will still last forever if you intentionally let the car gently jerk around from very fast pedal motions. It also helps if you resist the car with your brakes to slow the engine until you actually feel it throbbing from wanting to stall and then let go of the brakes just long enough for it to recover before slowing back down to a throb. The point is that you can't predict how long a clutch will last when driving techniques have a drastic impact on the rate of wear.

[Eagle1984]

A clutch can last anywhere from 60K to 200K miles, depending on driving habits. The key to long life on a clutch is fast shifting. Thats counter-intuitive. The gripping surface on the clutch lasts forever if its cold. It sheds off material considerably faster when its warm, and insanely fast when its hot. In an exaggerated sense, the rate of wear is exponentially related to the temperature of the material. If you pull your clutch pedal back very slowly the car will smoothly start rolling. If you let the clutch out very fast, the car will jerk and toss your head around and the engine will probably stall. The smooth start requires the clutch to come into contact with the flywheel and slide against the surface, which heats it up quickly while the jerking start requires the clutch plate to contact the flywheel and almost instantly mate to it and begin spinning together without any sliding or any heat buildup.

In stop and go city traffic your clutch will heat up from many consecutive shifts. It will still last forever if you intentionally let the car gently jerk around from very fast pedal motions. It also helps if you resist the car with your brakes to slow the engine until you actually feel it throbbing from wanting to stall and then let go of the brakes just long enough for it to recover before slowing back down to a throb. The point is that you can't predict how long a clutch will last when driving techniques have a drastic impact on the rate of wear.

Thanks again, so basically with a open differential is one is not engaged the power will go to it as it has the least resistance and not move compared to a closed one where it will move if one is disengaged. Does the clutch still wear out the same if it is a automatic? Are you saying that if the front axle does disengage for some reason it will not hurt anything and if it is a closed differential/transfer case even if they do disengage the front tires will still spin like they were engaged?

[captspillane]

It might suck to have to reach into your glove compartment for the emergency 9/16 wrench and have to crawl under the car in the rain along the side of Route 78 with your feet on the drivers side inches from the passing trucks to click the transfer case into 2WD. Yes indeed that does suck. No mechanical damage will occur. If your viscous coupling is strong it will make the front driveshaft spin along with the rear driveshaft but it won't matter because the wheels won't slow or restrict the movement of the driveshaft.

I'm not sure how to answer your question about a clutch wearing out in an automatic transmission. My earlier post was specific to the clutch in a car with a manual transmission.

[captspillane]

In an Automatic there are clutches, but they do a different job. The torque converter converts the engine torque into fluid pressure by using the spinning flywheel to drive internal turbines that move around fluid and imparting potential energy to that fluid. The main reason that automatics get terrible gas mileage in comparison to manual cars is that the torque converter is always putting a load on the engine and always robbing energy even when the car is sitting still. On a manual car the engine is totally disconnected from the rest of the car once the clutch pedal is depressed, so the only fuel necessary to keep it running is enough to compensate for the friction and resistance in one rotation of the crankshaft and associated internal components. That's minimal. Around each planetary assembly inside the automatic transmission is a clutch band that tightens down around the outside of the planetary to stop it from spinning or to let it spin freely, which makes the output shaft of the transmission go from stationary to spinning in a similar fashion as our differential discussion. Those clutch bands work off fluid pressure, so if the pump isn't putting out enough fluid pressure or if the throttle body can't maintain fluid pressure because of excessive leaks from antique gaskets then they can't engage fully. Clutch bands generally last for 300K+ miles but will quickly burn up and get ruined if they slip and heat up because of poor fluid pressure or a defective servo. There is also round clutch discs stacked together with steel discs in some of the internal assemblies that ease the impact of gear changes. Those also generally last forever unless they get damaged because of some other internal problem.

[mick]

Counter-clockwise is 4wd and clockwise is 2wd.