Evil Drew M

I helped a friend swap an AW4 recently. His Jeep is a 91 or 92 (Don't remember). We pulled an AW4 out of a 1995.

We had no issues getting it in. We used his flywheel and a new torque converter. Fluid level is correct.

With the Jeep on jack stands the tires spin when in gear but the Jeep won't move (seems like a low pressure issue). Point being it isn't a linkage issue.

My question is whether or not the TCUs are different? It is possible the "new" trans has issues but want to rule out everything else first.

Although I used to be a mechanic we never did trans work so I admittedly don't know much about them beyond the basics needed to determine that it needs to go to a trans shop.

dukie564

try disconnecting the TCU and shift it manually to rule it out. Doesn't sound TCU related though (they are the same), I think you may have gotten a bum tranny that won't stay in gear.

Does it happen in all gears? If the manual shifting test fails best get a pressure test done

Evil Drew M

Yeah it happens in all gears. It won't move under it's own power and will only turn the wheels if they are off the ground.

I agree that it sounds like the trans but as I said - my knowledge is limited to basic stuff and RnR. It is a pretty straight-forward job though and it either goes together or it doesn't. Not much room for "mistakes" that go un-noticed.

I really don't want to pull that F'ing thing again . . . haha! I helped him pull it at the pick n pull, helped him pull his old one and helped put this one back in.

excess650

Basic troubleshooting for an AW4 is to unplug the TCU or pull its fuse and try to shift manually. If it works manually but not with the TCU in play, its an elctrical issue. If it doesn't work manually, its most likely internal.

Did you test the NSS? You can check continuity between pins on its connector to verify what gear it thinks it should be in.

Do you have the AW4 manuals? If not, PM me your email address and I'll send 'em as attachments.

IIRC, 92-96 use the same TCU. '91 still has the comfort/power switch, so different shift points in the different settings.

If you wanna drive 20 miles past Mount Airy you can come and get my '88 MJ, pull the trans and part the rest.

Evil Drew M

By shift manually you mean using 1, 2, etc?

Outside of double-checking our work and jacking it up (the trick if you didn't fill the TC before installing it) we haven't done anything since we had a hurricane to deal with. FWIW I didn't unplug the stuff up top but I do remember what stuff I plugged back in and that wasn't one of them.

excess650

There are 2 connectors beside the trans dipstick. The 8 pin is for the NSS and the grey 7 pin is for the TCU.

Manually, yeah, R gets you R, N gets N, 1-2 gets you 1st until 4500rpm when it should pressure shift to 2nd, 3 with get you 3 and D will get you 4th which is a .75 OD.

hmmm I wonder if the TC is the problem

Evil Drew M

I got it then. For some reason I was thinking it was a smaller 4-5ish pin connector.

the buddmang

What everyone else has already mentioned, disconnect the tcu and try it. You should have foward and reverse, if not, check to make sure you have a filter on the trans. While you have the pan off, check for water damage. If the fluid is pink and milky you might as well get another trans to swap in.

The glue that companys use on the clutch plates is water based, if you introduce any kind of water into the trans it will wipe the friction material right off the clutch plates....