Electrical Experts AW4 Mod question.

[eaglefreek]

I'm am going to be installing an AW4 transmission from a Jeep Cherokee into my Eagle to gain overdrive. It is an electronically controlled transmission. I have all the wiring figured out, it's rather simple actually, but I have one mod I want to make. The one downfall of the AW4 is that you can't select first and second gear independently. The gear selector has one location for first and second and the TCU, transmission control unit, decides what gear to put it in based on output shaft RPM and the throttle position sensor. There are two solenoids that are involved with first and second gear. Solenoid 1 is on and solenoid 2 is off for first gear.  Solenoid 1 is on and solenoid 2 is on for second gear. Others have used 2 toggle switches to either de-energize or energize solenoid 2 depending on which gear they want to be in. I want to use one switch. In my wonderful drawing below is a three position rocker switch. In up position, power will be taken away from solenoid 2 to keep the transmission in first gear. In the down position, 12vdc will be supplied to solenoid 2 to keep it in second gear. In the middle position it would run as designed allowing the TCU to energize solenoid 2 when it wants to via the jumper with a diode. Am I on the right track? Don't have a clue? Is there another switch that will allow me to do this easier? What type of diode for the jumper and should I have a diode on the relay between 85 and 86? Does there need to be a load on 87 when the relay is open? THANKS! Here's an article with using two toggle switches. http://www.fourwheeler.com/techarticles/drivetrain/129_0606_aw4_jeep_cherokees_transmission_lock/index.html

[rohnk]

I don't know anything about these transmissions but the principles are solid. I would worry about "switching transients" and/or arching from the switch depending on how much current is being switched. From the article you referenced, the 1N4002 is a general purpose rectifier that is very common and used in many applications. In this case, your need for the diode is to prevent feeding +12Vdc into the TCU output.

The 4004 and 4006 are better for reverse voltage ratings. This would be better in the case of switching transients caused by sudden changes in voltage. The 4004 in particular has a higher internal capacitance which will also help to smooth these peak voltages out. Why am I worried about this? Because I dod not know how robust the electronics in the transmissions are and I don't know the specs for the TCU inputs/outputs. Better to go with a slighty larger rated diode that is more common and be safe. They all operate at the same currents which is 1 amp.

Using two switches is also a safer option IMHO. Using a double ended rocker may lead to an accidental switch if your elbow hits it on a big bump. Two switches also removes some of the confusion (at least for me). Also, if you use lighted switches, you can use different colors for each gear in case your wheeling a little late into the evening or early in the morning.

[eaglefreek]

Thanks for your input Rohn. I think two switches would be confusing for me. So the 1N4002 should probably be fine? I posted this on another forum and a guy made a good point that I could use a single pole switch, instead of a double pole, by just attaching the line coming from 87a right to solenoid 2. He also changed my diagram in case I wanted to install some idiot lights which I just may do.

[shaggimo]

  This is one mod I've been meaning to do, I'll be watching to see how you make out, if you don't mind me looking over your shoulder, lol. 

[eaglefreek]

This is one mod I've been meaning to do, I'll be watching to see how you make out, if you don't mind me looking over your shoulder, lol.  

Not at all. It might be a few weeks before I have it all said an done and I plan on doing a write up to make it easy for others. I still have a couple parts to collect to convert the 2000 Aw4 I have, into an earlier one. I may also take it to a trannsmission guy and have a Transgo reprogramming kit installed also. The more research I do, the easier the swap seems, except for muscling the trans in and out of course.

[shaggimo]

Nice, shift improver kits are pretty straight forward, never done one on an aw4, but several on gm trans'.  Don't go too far, I made that mistake on my car, now I can't use my cd player around town,  , and for some odd reason my rear tires are prematurly going bald  . lol

[carnuck]

This is one mod I've been meaning to do, I'll be watching to see how you make out, if you don't mind me looking over your shoulder, lol. 

Not at all. It might be a few weeks before I have it all said an done and I plan on doing a write up to make it easy for others. I still have a couple parts to collect to convert the 2000 Aw4 I have, into an earlier one. I may also take it to a trannsmission guy and have a Transgo reprogramming kit installed also. The more research I do, the easier the swap seems, except for muscling the trans in and out of course.

Transgo doesn't make a kit for them AFAIK. It's all electric solenoid and computer controlled.
Search AW4 shifting

[eaglefreek]

This is one mod I've been meaning to do, I'll be watching to see how you make out, if you don't mind me looking over your shoulder, lol. 

Not at all. It might be a few weeks before I have it all said an done and I plan on doing a write up to make it easy for others. I still have a couple parts to collect to convert the 2000 Aw4 I have, into an earlier one. I may also take it to a trannsmission guy and have a Transgo reprogramming kit installed also. The more research I do, the easier the swap seems, except for muscling the trans in and out of course.

Transgo doesn't make a kit for them AFAIK. It's all electric solenoid and computer controlled.
Search AW4 shifting

The link I posted says otherwise and others in the Jeep community have used it. I have no desire to have a manual box. I want it to work like an auto transmission and if I get into any bad stuff and need to keep it in first gear, I want the option of  doing that.

[shaggimo]

http://transgoonline.com/products.php?prd=340-HD2&homeinclude=catalog&category_id=149&parent_id=45&product_id=254&countdisplay=1&start=0&addcountview=Yes

Changes the springs and  a couple valves with in the body, higher pressures, quicker springs, = your firmer shift. It shouldn't change anything with the electronic end.

[captspillane]

Transgo doesn't make a kit for them AFAIK. It's all electric solenoid and computer controlled.

Shift kits will always be available for automatic transmissions, regardless if they are considered "Hydraulically controlled" or "electronically controlled". They both use the exact some components and operating principles to function.

Electronically controlled transmissions have solenoids that open and close passages in the valve body. That controls when it shifts, but not how it shifts. Spring pressure and circulation of hydraulic fluid is still the deciding factor in its operation.

[anrkii]

Just buy one of these, and throw ALL of the electrical crap away.

http://www.radesignsproducts.com/Baja.html

They have a little version of it for $85 as well.

I love manually shifted autos!

[eaglefreek]

I've seen those. Honestly, if I wanted to shift, I'd get a manual transmission and get the full advantage of a manual transmission. I've been working out of town too much and haven't had a chance to tackle the swap yet. Heck, I don't think I have driven my 86 Eagle in over a month.

[captspillane]

The measurements I took between bellhousing surface and trans mounting surface:

25-1/4" long for my 1992 AW4
22-3/8" for TF998
22-1/2" for TF727

24" for my AX15/NSG370/NV3550
21-3/4" for T5/T4/SR4

How do you plan on accounting for the extra three inches of length for the AW4? I'm also planning this same swap and have been interested in doing the same wiring upgrade this thread is about.

My plan is to use a NP242 behind the AW4. I already have an NP242 now with an XJ slip yoke added directly to my original driveshaft Ujoint. My original Eagle driveshaft has a three inch piece of pipe added to limit the range of the old slip yoke, necessary to keep both slip yokes from working together and letting the driveshaft fall out of place. I figure I can use an original driveshaft without a problem because the driveshaft will be at the extreme bottom of its range of motion, making it three inches shorter than it currently is. That solves my rear driveshaft difference without any effort.

On the front driveshaft there is about an inch or two of adjustment available from the slip yoke, necessary to keep the engine vibrations from damaging the Ujoint. Because the front axle is bolted directly to the engine the driveshaft doesn't need a slip yoke in a sense. The actual range of motion it needs to provide is less than an 1/8" inch, even though the slip yoke is several inches long. It may work as is with the AW4. If it doesn't quite reach I hoped to use a longer output yoke on the transfer case. Here is a picture of three output yokes lined up. They came from a NP242, a NP249, and an Eagle NP129. I forget which is which except that the shortest is the Eagle one. Normally I switch to the shortest one, the original Eagle yoke, when I install an NP242. I figure I can just keep the NP242 long yoke or find a 249 long yoke to make up for an inch or two of the three inch difference in length. That should make the front driveshaft work as is.

[eaglefreek]

How do you plan on accounting for the extra three inches of length for the AW4? 

 

I was going to tackle that when I got to that point.

[captspillane]

I was going to tackle that when I got to that point.

I think that's funny. I put alot of thought into the driveshafts and other mechanical details but dismissed the electrical details as something to worry about after I have it all bolted together. You're pregaming for the swap by researching the electrical details and you're dismissing the bolt together details as something to worry about along the way. I think it's an ironic difference in perspective.