AW4 Weak Reverse

I've got a 1996 XJ with an AW4 that has a very weak reverse gear. I mean it's so weak the previous owner didn't think it worked at all, it will move the Jeep on a flat smooth ground but if it gets any resistance it will stop no matter how much gas you give it.

With the TCU unplugged first, third, and fourth work just fine, reverse is weak with the TCU plugged in or unplugged (as you would expect).

Now I don't have a lot of automatic transmission experience but by looking at the book I'm thinking it might be a physical blockage in the manual shift valve in the transmission? It can't be a first/reverse clutch issue because first has the right pull.

So what do you think? Has anybody seen this issue before, if so what did you do to repair it?

The transmission only has 120k on it but there was an unsmart previous owner involved...

Thanks

A fluid change with the correct fluid might be a good place to start. The PO might have used ATF4+. Check the throttlebody-tranny cable as well.

X2 on atf fluid change. --DEXRON/MERCON 3 ONLY.--

-?weak solenoid?

Good Luck,
Orange

P.S. if the fluid change do it, suggest another change after few hundred miles

Well on some further looking into it I'm still guessing a blocked passage. Whoever last sealed this transmission up used way too much RTV and there were globs of it on the inside of the transmission. I guess I'll be pulling the valve body off and inspecting it. Fun stuff!

Careful of the check balls and springs. Never had an AW-4 apart but a Turbo 400 has several balls and springs.

Well there was a clip that might have been out of position, I'm not sure if it was out or if it just slipped when I was taking it apart. Other than that the gaskets between the upper/lower valve body separation plate looked like hell. I'm going to pick up a valve body rebuild kit to replace the check valves and gaskets and button it back up.

It'll probably be a week before I can do this (not exactly the kind of part you can pick up on a Sunday afternoon). I'll update this thread with my findings.

Today's work, I'm too lazy to type it out again.

http://www.boyandjeep.com/2009/10/18/aw4-madness

Teaser pic:

i wonder where the check ball went? unless somebody has been it it before?

x99j said:

i wonder where the check ball went? unless somebody has been it it before?

Click to expand...

I know that at the very least somebody has changed the fluid / filter, more than that I cannot tell you. It's possible somebody took the valve body apart and lost the ball though. It is also remotely possible that the check ball was defective and broke up (they are not metal, they are a plastic or maybe hard rubber).

I'm going to try to find the parts somewhere, I know I can get them from a dealership in New Jersey (ChryslerPartsDirect.com) for a little over $40 but I need to have them by next weekend, we'll see...

GSequoia said:

I know that at the very least somebody has changed the fluid / filter, more than that I cannot tell you. It's possible somebody took the valve body apart and lost the ball though. It is also remotely possible that the check ball was defective and broke up (they are not metal, they are a plastic or maybe hard rubber).

I'm going to try to find the parts somewhere, I know I can get them from a dealership in New Jersey (ChryslerPartsDirect.com) for a little over $40 but I need to have them by next weekend, we'll see...

Click to expand...

Same box in the Toyotas, can't tell you the models, try their dealers.

joe_peters said:

Same box in the Toyotas, can't tell you the models, try their dealers.

Click to expand...

Yeah, dealerships are annoying though

GSequoia said:

Yeah, dealerships are annoying though

Click to expand...

I think Autozone has a master rebuild kit, but it is $100 or so.