Traction Improvement Devices

[captspillane]

Its just a reference point for comparison. Its alot easier to relate to than an expression of ratios. Its a good reference chart for any car, any size, any engine, any horsepower, any hill.

Every gasoline engine has a similar RPM range and a graphically similar power and torque curve. At 500 RPM a 401 V8 is almost as useless as an Iron Duke. At 10,000 RPM both an Iron Duke and a 401 will explode.

If in 5th in my SX4 you can go 95 MPH at 2500 RPM then you can go 19 MPH at 500 RPM or 190 mph at 5000 RPM. The engine won't mind. Any RPM is fair game in any situation, but obviously people consistantly use a much more narrow practical range of speed and RPM for any given gear.

[captspillane]

That's true, I chose 2500 RPM because I'm talking about 4.2, 4.0, and 2.5 Eagle engines with stock or near stock camshafts. A Subaru Forester has a tiny engine that is set up to operate at a much higher range of RPM's. That would need a totally different reference RPM closer to 3500. Likewise my four speed turbodiesel Scout has a very different target RPM. A drag race car isn't designed for stop and go city traffic, it's designed to operate exclusively in its high power low longevity RPM range.

My actual "gearing calculator" is an excel spreadsheet showing several reference RPM's, every tire size I own, and every Jeep and Scout transmission I own. Its huge. My immediate family owns 41 cars and I have information for all of them. It took me several days to create the spreadsheet.

I only typed one tiny sampling here to demonstrate the effect of 2.35 versus 3.54 in an Eagle. It takes alot more information to decide what gear ratio you want in your car.

Its much more concise if we only talk about stickshift Eagles and stock Eagle engines with tires similar in size. I can tell you that 3.54 is a perfect match for a T5 or AX15, 3.07 is nearly as good a match and sometimes a better match if you have a different driving style than me, and 2.35 is no good for anyone anywhere. If you have a four speed 3.54 is too low. It will give you a top speed with the engine screaming around 80 MPH. You should use 2.72 or 3.07.

[standup650]

my four speed turbodiesel Scout

I have a 1966 800 and I've thought about this. Have you posted about it or have pics?
Sorry not trying to change topics. Also posting to follow topic. But Scouts do make me smile!

[mach1mustang351]

Still no progress on my end on this project.  I am waiting on tackling anything until I know for sure I can get my 3.55s up front which as we have covered in dept other threads requires the 4 cyl front axle.  Not a lot of AMC donor cars here in AK so this may be tough situation for me. 

[captspillane]

Yes I have posted about my 1980 Scout. It is currently my daily driver until my primary SX4 is complete. I bought the Scout because it came with a spare turbodiesel engine and it was mechanically sound with lots of rust repair already complete. I've since purchased a second long wheelbase Scout  with Terra pickup truck cap.

The SD33T has very similar dimensions and output, both horsepower and torque, to a stock AMC 258. Its underpowered for the Scout but its perfect for an Eagle. I'll be converting the Scout to a 6.2L GM diesel or a Cummins diesel. The SD33T will be mated to a NV4500 five speed, with a special IH North adaptor kit, and then installed in an Eagle.

Here is my project thread.

http://forums.amceaglenest.com/index.php?topic=36383.0

[carnuck]

my four speed turbodiesel Scout

I have a 1966 800 and I've thought about this. Have you posted about it or have pics?
Sorry not trying to change topics. Also posting to follow topic. But Scouts do make me smile!

You need more length under the hood. (late model Scouts came stock with the SD33 and '80 came with SD33T) 4 cyl Nissan turbo diesel would fit better. The 6 cyl is used in Full size Jeeps except in the US.

Back to the ratios:
Determine what speeds you will need to drive at the most (for example, we have 70 mph zones on the highway here and spots where it's like LA in rush hour).

What loads? (I often haul trailer or heavy loads)

What motor? What's it's power curve?

Tire size?

[captspillane]

Nope, you don't need more length under the hood. It fits. The other thread talks about that. I own a 1980 turbodiesel as my daily driver.

Realistically all the thought and figuring in the world doesn't make much difference with the gear ratios. There's only four choices for an Eagle, and one of them is obviously junk. If your car is roadworthy (I don't consider drag racing cars roadworthy) then its going to work with the three choices.

All three of them work fine for any engine and any camshaft available. It's all preference from there. I drove my 2.35 T5 SX4 for several months with just some mild griping.

[carnuck]

I meant the early Scout needs more underhood length to fit in a 6 cyl Nissan diesel like the Scout II (they quit calling it that before 1980). They mostly came with slant 4s (304 IH with 1 bank cut off) I did a 6 cyl 200 Ford swap into one and the firewall had to be notched to fit.

As for gears, tires make a huge difference in what ratio you'd want. Slammed lowrider would want the taller gears, even with an O/D.

As for ratios, I found out the '80 I parted had an oddball one. 3.31 with class 3 tow package (Is there a full list on Eaglepedia?)

2.37, 2.72, 3.08, 3.31, 3.54, 3.73 and 4.10. Any 4.56s? Any missing?

[BenM]

As for ratios, I found out the '80 I parted had an oddball one. 3.31 with class 3 tow package (Is there a full list on Eaglepedia?)

2.37, 2.72, 3.08, 3.31, 3.54, 3.73 and 4.10. Any 4.56s? Any missing?

I don't believe as such, but the 79-83 parts catalog lists a whole mess of available AMC 15 and 20 ratios.

As far as I can tell (F/R)
2.35/2.35 (20:47/17:40)
2.72/2.73 (18:49/15:41)
3.07/3.08 (14:43/13:40)
3.31/3.31 (13:43/13:43)
3.54/3.54 (13:46/13:46)

...Those are the factory Eagle ratios offered. The lowest gears (4.xx) are available aftermarket for CJs; I don't have any Jeep TSMs available to see if there were other options from AMC.
The 3.0x and 3.54 gears are easy to come by for replacement but 3.31, 2.7x and 2.3x sets are hard to find. They exist, aren't necessarily more expensive, but are just harder to find.

[Einsteins Eagle]

Are these 'soft lockers/centrifugal' parts along the same lines as the 'Lunchbox Lockers' I have read about?  I'd like to get a little bit better traction in my '80 sedan, do not have the resources easily at hand to do major welding mods in the way of axle swaps, and am liking the fuel mileage (albeit pokey) performance of the long-legged gearing.  The 2-speed transfer case takes care of tall gearing off-road for my needs.  Please if I may ask, what and who is a source for these devices?  I'm sure I could install it myself, reading you keep the same carrier and do not have to disturb crown/pinion during the project.  How noticeable is the unit on the road, does the device make the Scrambler jump sideways badly in a turn if it locks up suddenly, especially in the wet?  Thanks in advance for any input, Howie

I have a centrifugal unit in my Jeep Scrambler. Its effective, but it has a noticeable effect in curves. My sister refuses to drive it because of the soft locker. Their biggest advantage is that they can be installed quickly and easily. No change to the carrier is necessary. As a wheel loses traction and the wheel begins to spin much faster relative to the other, the centrifugal force locks the two halves together. It clunks together and often causes an audible tire screech. The clutches in a limited slip differential are much smoother and less likely to scare the driver, but in some ways that makes them less effective than a soft locker.

A hard locker is much more expensive and harder to install. The one I want to buy for my 401 5 speed SX4 is electric. Its a limited slip until you push the button and then the axles are fully locked together. My Rubicon has this option front and rear and I absolutely love them. Most of us would never install one since they're worth more than the average Eagle. I think a soft locker costs about 300 dollars and a hard locker 1200 to 2000 dollars. A limited slip differential is expensive unless you buy a whole axle with a factory unit already installed.
[/quote]

[PR1AWRet]

Look at my reply on this thread it gives the proper name for the different traction aiding differentials.  It is post #21.  If you are talking about a lunch box locker, they are not centrifugal.  The only centrifugal locker I know about is the Gov-loc used on older Chevys. 

[Einsteins Eagle]

Look at my reply on this thread it gives the proper name for the different traction aiding differentials.  It is post #21.  If you are talking about a lunch box locker, they are not centrifugal.  The only centrifugal locker I know about is the Gov-loc used on older Chevys. 

Thank you very much, the primer in what is what helped indeed.  I was sort of thinking this is what was meant the the centrifugal unit indeed being the Gov-Loc.  I will look into the many options seeing there is much available for the AMC15/Dana35's.

[captspillane]

I'm sure I could install it myself, reading you keep the same carrier and do not have to disturb crown/pinion during the project.  How noticeable is the unit on the road, does the device make the Scrambler jump sideways badly in a turn if it locks up suddenly, especially in the wet?  Thanks in advance for any input, Howie

I disagree in the proper names listed earlier in the thread and I especially disagree with the comment that the only "centrifugal" unit that exists is one obscure type. Forums are full of such silly arguments. That's as ridiculous as objecting to calling an AMC Eagle "All wheel drive" just because the factory didn't use the term (Subaru coined the term in 1984, long after the 1980 Eagle's pioneered the concept). Another favorite of mine was the recent arguement about the definition of "coupe." Who cares about the names, we just want to discuss the options you have to spend money on.

I personally have just two categories for full time automatic units. I look at the options as "Centrifugal" or "Clutch type Limited Slip" to mean it either needs a new carrier or it doesn't. In other words the installation is either expensive and hard or cheap and easy. Either I would install it in a car my grandmother owns or I wouldn't.

If you punch in "dana 35 locker" as a search term into ebay you'll see a huge list of lockers that retail between $270 and $350 new under such names as lunchbox locker, soft locker, Powertrax, Spartan, Lock Right, etcetra. Those are great because they are very cheap and easy to install. You can install them into your existing carrier in almost no time flat with no special tools or skills. I call those "centrifugal" lockers because they consist of two halves seperated by springs that have teeth built into them. As the wheels spin relative to each other the springs keeping the two halves and their teeth apart get pushed in through centrifugal force. When the teeth come into contact they crunch together with a dramatic jerk. If you continue to accelerate the two halves remain locked together. You need to back off on the gas pedal before they release. When they release it can be just as dramatic as when they lock up if you're driving aggressively.

That is what my Scrambler currently has. It sucks. The tires chirp around tight curves and the sudden jerk as it engaged frightened my sister. I'm used to it and I don't care much. I certainly would not justify a nicer locker in the cheap Dana 20 axle I still have in that truck. It works fine and I generally like it. It does not have a dramatic impact on driving quality if you take your foot of the gas during the curve. The heavy jerk really only happens when you try to accelerate through the curve aggressively.

Do you drive the car to work every day and on the beach several times a year? Install one. Does your trophy wife and your grandmother drive the car as often as you do? Don't install one and invest that $300 toward a better, smoother unit.

Most people call factory limited slip differentials "Positraction" just like they call tissues "Kleenex." That broad category of clutch style limited slips are very nice and very smooth working. They are much more expensive and they generally wear out in ways that a lunchbox locker never would. You must replace the whole carrier to install one. There are plenty of options for all budgets.

[captspillane]

Here's some stuff I found in a quick ebay search. I disregarded all the lunchbox lockers because I personally will never install another one. I loan my cars out to all my family and friends and I will always choose to pay a little more for a quality driving experience that I can be proud of.

I also disregarded all the typical offroad lockers that are designed to be an open differential on pavement and then fully lock while offroad. Those don't help improve traction when you drive to work.

Here are some options I found:

-Detroic "Truetrac" advertises the smooth operation of a true OEM limited slip without the need to replace the clutch packs or use the oil additives. They seem like the foremost choice. There was one vendor offering several new units for $400 and several people selling them for about $550.
-"Trac-Lok" is the Dana Spicer term for the OEM style limited slip. It has a replaceable clutch pack and requires additive to the differential fluid. It works very smoothly and might be available used. There was an auction there with a buy it now of $289, but generally these are more expensive closer to $400 brand new.
-"Powr-Lok" is OEM style with a replaceable clutch pack.
-"Yukon Positraction" seemed to be a style similar to the OEM Chevy version of the "Trac-Lok."
-"Auburn Gear Positraction" was an interesting option. It was relatively cheap at $285 and it looked like a normal lunchbox locker in the diagram. The difference was that it was advertised to have cone clutches and it seemed to require the replacement of the whole carrier. It seemed to be vastly better than a typical lunchbox locker but not quite as nice as a usual limited slip. That might be a great option for some people.

-I didn't find it but Detroit does make an Electric locker very similar to the older Rubicon electic lockers. Those are awesome. They cost about $1200. It acts as a very smooth limited slip in normal operations but it can be fully locked with a button in the cab. That's the ideal locker for someone with a big budget and high standards. I plan on using one in my nicest Eagle. I already have the factory version in my 2006 Jeep Rubicon and I love it.

FYI the older AMC designed 2004-2006 Jeep Rubicons had electric lockers that acted as limited slips until locked, while the newer all Chrysler Jeep JK Rubicons do not act as limited slips. They only electonically lock.

[PR1AWRet]

-I didn't find it but Detroit does make an Electric locker very similar to the older Rubicon electic lockers. Those are awesome. They cost about $1200. It acts as a very smooth limited slip in normal operations but it can be fully locked with a button in the cab. That's the ideal locker for someone with a big budget and high standards. I plan on using one in my nicest Eagle. I already have the factory version in my 2006 Jeep Rubicon and I love it.

FYI the older AMC designed 2004-2006 Jeep Rubicons had electric lockers that acted as limited slips until locked, while the newer all Chrysler Jeep JK Rubicons do not act as limited slips. They only electronically lock.

Eaton E-Locker.  Detroit is a sub division of Eaton.

I agree on the newer Rubicons, But I said a variation meaning not all.

If we ALL use the proper nomenclature, we will ALL be on the same page.  

That is all I will post on this subject here.  It's not a mine is bigger than yours contest.