89 AW4 shifting problems

My XJ is having problems shifting properly. I was driving the other day and noticed it shifting much later than normal, but that was the only symptom. Later in the day, I was driving about 30MPH, and it acted like I shifted into Neutral. I could rev the engine, but I wasn't getting that power to the drivetrain. After a little revving, it engaged again and I pulled into a gas station. I have been having issues with a bad negative battery connection, but I have resolved that issue.

When I put the shifter in 1-2, or 3, it does the same behavior.

The fluid level in the trans looks fine.

The fuse to the TCU has been replaced, even though it was not blown.

I have a brand new TPS, but would it cause that symptom?

I have no confidence to take the thing more than a few blocks. Late shifting is one thing, but cruising along and having it disengage is very bad.

It only "disengaged" once, but I haven't driven it much.

Any thoughts?

Your fluid may be up, but the filter might be clogged....

Change the fluid and the filter and see if that improves it's attitude....

I should say I have not installed the new TPS.

I will try a fluid and filter change, when I have a chance to go to the parts store. This is my DD.

If it suddenly disengaged then I doubt it's the TPS

Maybe the torque clutch converter is failing

ehall said:

If it suddenly disengaged then I doubt it's the TPS

Maybe the torque clutch converter is failing

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I was thinking the same thing, other than a real malfunction with the trans. Like I said, I was cruising along and it felt like I threw it in N. After a few revs, it re-engaged.

Hmmm...

Am I thinking correctly that the AW4 can be removed without pulling the engine?

Anyone else have any suggestions on this issue? I would hate to do all of that work and not have it fix my problem.

It is a good thing I live near the light rail system.

The trans can definately be removed from the bottom. You will need an E12 socket for the top two trans/motor bolts, other than that it's all basic hand tools.

Bad TPS can cause the late, or early shift problem so replace it. For the stuck in neutral change the filter and fluid, use Dexron III/Mecon, not mecon V, or anything else. Do not use synthetic Tranny fluid either. Take two aspirin, say lots of prayers to the Jeep Gods, and try it again!

ehall said:

If it suddenly disengaged then I doubt it's the TPS

Maybe the torque clutch converter is failing

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Could just be some varnish/trash that came loose and stuck in a valve seat area temporarily, if he is lucky. He should drop the pan and take a look see at the filter and pan bottom for trash, oil parts....

Slo-Sho said:

The trans can definately be removed from the bottom. You will need an E12 socket for the top two trans/motor bolts, other than that it's all basic hand tools.

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Why even pull it at this point?

Ecomike said:

Why even pull it at this point?

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Because it does the same in 1-2.

poorboy_616 said:

Change the fluid and the filter and see if that improves it's attitude....

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There *IS NO FILTER*.

There is a 'screen', but its got GIANT holes in it and wouldnt hold anything much smaller than metal shavings. I think the screens on my bedroom window are a finer mesh.

to the OP:

Unplug your TCU (its under the dash right over the passengers knees) and go for a drive. That will eliminate anything electrical. If you still have problems, proceed with pulling the trans.

Its time consuming but not a difficult job. Be sure to support the engine.

89CherokeePioneer said:

Because it does the same in 1-2.

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Not sure that means anything. In 1-2 it always shifts to 2 real late, like at 4000 rpm.

A bad TPS can cause late shifting, and other odd behavior. He said it stuck in neutral, but only once so far, and then it fixed itself. That is not enough justifcation to drop the transmission. Run more tests, with the TCU disconnected as Cal said, and visual inspections by dropping the pan first. Hell it could be a bad vehicle speed sensor at this point! He has not run enough road tests yet. Or it may just need some seafoam or TransX to clean and flush the varnish out of it.

cal said:

There *IS NO FILTER*.

There is a 'screen', but its got GIANT holes in it and wouldnt hold anything much smaller than metal shavings. I think the screens on my bedroom window are a finer mesh.

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OK, but someone a few days ago here said they changed their filter (or screen) on the AW4, as it was totally clogged with clutch material, and it fixed their neutral, slipping problem.

Are the AW4 replacement aftermarket filters that course???

In summary, in the following order, replace and calibrate the new TPS sensor. Disconnect the Battery for an hour. Reconnect the battery, disconnect the TCU, and test drive it using the shifter like a manual stick. Note that in 1-2 it will not shift into 2 until about 4000 rpm, so you can shift to 3rd at 2500 rpm if you choose to.

If the neutral slipping problem returns, then drop the pan, drain the fluid, replace the screen or:dunno:, and then add fresh fluid. If it persists I would try a can of TransX or Seafoam before I started doing real work on the tranny.

Now, why can 't the valve body be pulled and serviced while the tranny is still installed? Not mention running pressure tests before dropping the Tranny?

cal said:

There *IS NO FILTER*.

There is a 'screen', but its got GIANT holes in it and wouldnt hold anything much smaller than metal shavings. I think the screens on my bedroom window are a finer mesh. I did not know that about the AW4, I was thinking it took the fine mesh or cotton type filters that other trannies do...

to the OP:

Unplug your TCU (its under the dash right over the passengers knees) and go for a drive. That will eliminate anything electrical. If you still have problems, proceed with pulling the trans.

Its time consuming but not a difficult job. Be sure to support the engine. The trans will have to be shifted manually with the TCU unplugged, so have fun!!

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Comments in bold

Thank you all for your help. I am going to try your suggestions and do more road tests.

Just for the sake of clarity, I had the shifter in 4 and was moving when it seemed to "slip" into Neutral. The shifter did not move and there was no strange sound I noticed. I just wasn't moving along how I should have been.

It will be a few days until I have my parts and fluid together for the change.

I will post up my findings/results.

Thanks again!

I say start looking for a trans now. Lot's of hopefuls in here thinking fluid changes will bring back a slipping trans heh. As far as the TPS, you can check that with a multimeter to verify that it is good.

Slo-Sho said:

I say start looking for a trans now. Lot's of hopefuls in here thinking fluid changes will bring back a slipping trans heh. As far as the TPS, you can check that with a multimeter to verify that it is good.

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He said he already has a new TPS that he just hasn't installed.

cherokee89,

How long have you had this Jeep? How much do you know about the tranny in it? Have you ever changed the fluid since you bought it? Is it an 89?

I had the same problem with my '88. Tranny fluid was normal and decent shape; flushed and replaced anyway, problem persisted. I had just replaced my valve cover gasket and had disconnected the throttle valve linkage to do it, well apparently that took it out of adjustment. If you have a Haynes manual go to Chapter 7 Part B pg 3 (7B-3) Section #4 Throttle Linkage - Adjustment it is very quick and easy to do. See if that doesn't fix your problem. If you don't have a manual you should get one, sometimes they come in handy, not always but sometimes. Good Luck

Get a manual for your transmission from ATSG they make very detailed shop manuals for complete teardown and troubleshooting.