erratic shifting (AW4)

Today my AW4 exhibited signs of erratic shifting, not slipping but more like it would kick up or down at the wrong times. It shifted fine for the first 200km that I owned it and now has started acting a little funny.

Here are the symptoms:

From start up, everything seems fine. After driving around 5 miles(and subsequently letting the transmission warm up) it started to show signs of erratic shifting.

I reached my destination(around 15 miles from home) and did some business, letting it sit for around 2 hours. Hopped in, drove home and the same thing..shifted fine with NO abnormal shifts or torque converter lockup for around the first 5 miles, then it started acting up again.

I bought this thing not too long ago, and it appears to have had the fluid/filter changed fairly recently(maybe even at the dealership where I bought it, since they did other tune up things at the same time--plugs, wires, air filter,new oil/filter, new 02 sensor etc--quite likely that they did the tranny at the same time).

The tranny fluid is at the right level(a hair above the full level, actually), checked both hot and cold. Fluid is nice and reddish, no signs of wear--it actually looks brand new. would the minute amount of extra tranny fluid cause these problems?
I'm wondering if there is a possibility of the wrong fluid causing these symptoms? The fact that everything shifts fine until it starts to warm up leads me to believe this may be the case. I have read it is quite common for the dealer to mistake the correct fluids and substitute ATF3 for the dexron2 the manual calls for.

To be more specefic about the "erratic shifting", it'll upshift fine into first, second, third and OD at the correct RPM's but when slowing down it will sometimes kick down from OD to 3rd rather erratically, rev to 3000RPM then get back into OD. It'll do the same thing between 2nd and 3rd occasionally too. I don't redline it at all, and accelerate really slowly to allow it to comfortably reach it's shift points instead of stomping it and forcing it to shift too quickly.

thanks!

I had a similar problem on my 1991 XJ, but it only happened when it hadn't been run in several hours and it was cold out. The dealership tech I talked to said that the previous owner had most likely neglected to change the fluid for years, then recently changed the fluid; this is bad because over the years crap starts to build up inside the tranny. When you introduce new fluids, they loosen the deposits and they can in turn stick in valves, gum up oil passages, or just otherwise ruin a tranny's day.

His advice? Drain some fluid off, and dump in a bottle of Lucas transmission treatment. It helped, but it was always an issue.

Does your problem persist after the Jeep has been running for a long time? Does it ever shift normally? The only other problem I can think of is that your valve body isn't able to hold the tranny in a higher gear when you let off the gas. It happened to my 93 ZJ with the 46rh tranny (one of the reasons I went BACK to an XJ!) and the mechanic said I needed a new valve body. (It wasn't as painful as you might think, it was under warranty for a tranny rebuild.)

I'm no expert though, hopefully someone else will be able to help more.

the jeep completely shifts normally until I have driven around 5 miles and I emphasize completely normal because it shifts like it was new, then on a tee all of a sudden it starts exhibiting the problems I described. When I bought it I took it for a test drive and drove it in a variety of conditions for quite a long distance as well as stomped it a few times to check it's shifting under hard acceleration and it didn't miss a beat at that time, and hasn't for nearly 200km afterwards. In fact just the other day when I finished my rear main seal the retired mechanic friend who's shop space I borrowed asked how the tranny was and I was happy to say that it didn't miss a beat.
All of a sudden, out of the blue it has started doing it this morning. The only thing I can think of is that after the fluid heats up, it become thin enough to cause some problems.
This *kind of* backs up the belief that I have that there may be the incorrect fluid in there...if ATF3 has a lighter viscosity than the dexron2 that the manual calls for, then it might cause some problems.


Does anyone know the viscosities of the different fluids? A quick google search didn't really turn up the info I was hoping for.

While you are checking out the transmission itself, fluids, filters, be sure to check the electrical items like the TPS and electronic transmission controller (TCU?) under the steering column. TPS Sensor connector to the tranny could have been lossened during all the work those people did, or the TPS could be going bad on the tranny side of the sensor (TPS).

I have had multiple transmission fluid problems with older chryslers/dodges. Luckily no jeep tramsmission problems yet, but you are asking a good question. When, if in doubt, I would get the right stuff and change the tranny fluid and filter ASAP.

Ecomike said:

While you are checking out the transmission itself, fluids, filters, be sure to check the electrical items like the TPS and electronic transmission controller (TCU?) under the steering column. TPS Sensor connector to the tranny could have been lossened during all the work those people did, or the TPS could be going bad on the tranny side of the sensor (TPS).

Click to expand...

A little googling and I found a few people talk about the TCU and a wonky voltage reading throwing off the transmissions shift points. I'll have to get out the voltmeter and do a little troubleshooting tommorow. The article I read revealed that the guy adjusted the voltage back to spec (I guess you can do that?) and that fixed his problem.
Does anyone have any insight on the TCU?

You need to check the TPS (throttle position sensor), not the TCU (trans computer). Pre 1991 TPS units could be adjusted by loosening the mounting screws and turning it slightly. A flaky TPS would not be unusual and can cause your symptoms. Also look at the tranny cable for proper adjustment and that can affect shift firmness. ATF and Dexron have similar viscosities, but rather different coefficients of friction.

lawsoncl said:

You need to check the TPS (throttle position sensor), not the TCU (trans computer). Pre 1991 TPS units could be adjusted by loosening the mounting screws and turning it slightly. A flaky TPS would not be unusual and can cause your symptoms. Also look at the tranny cable for proper adjustment and that can affect shift firmness. ATF and Dexron have similar viscosities, but rather different coefficients of friction.

Click to expand...

good to know, that's great! Could you please give me a bit more info on turning the TPS unit? Just had a look at my haynes manual and they say "the TPS on 1991 and later models is non adjustable". Of course, they don't give any info on actually adjusting the pre 1991 models.
thanks alot!

I do wonder if the TCU could be damaged in some way. I had a problem with the blower motor hose being disconnected and resting on the firewall. Long story short as soon as the blower motor was running, it would suck up any water sitting on the firewall and spray it all over the passenger floor--and I guess the TCU as well.
hmm, hope that didn't fry it.

Water and most Renix electrical devices do not get along too well with water.

If you have a multimeter, you can test the TPS easily first. It is a wear part that frequently wears out, and it is cheaper (new ones) than a TCU.

The TCU is real easy to reach and remove, just under the steering column. Just pull it out, and see if it got wet and or fried.

I have read recently that the transmission will work with the TCU disconnected. I forget the details, but they were discussing the TCU and transmision tests with out the TCU connected for troubleshooting. Something about manual shifting using first, and third versus Drive selection on the shifter.

clunk said:

Of course, they don't give any info on actually adjusting the pre 1991 models.

Click to expand...

Checkout this links, it was the first one that popped up when I googled "adjust Jeep TPS".

http://autorepair.about.com/library/a/1e/bl608e.htm

Intersting to note that they called the IAC an ISCV (Idle Speed Control Valve(?) which is I think what Autozone called it in their computer data base. I played hell finding the right name both times I had them pull one for me. They tried to tell me it was non stock item. I just had to give them the right, wrong name for it, LOL.:doh:

ISCV actually makes more sense if you think how it functions. The fun one is figuring out that the FSM and dealer call it versus what everyone else calls it. For example a CPS sensor is not a crankshaft position sensor, the FSM calls that a CKP.

lawsoncl said:

ISCV actually makes more sense if you think how it functions. The fun one is figuring out that the FSM and dealer call it versus what everyone else calls it. For example a CPS sensor is not a crankshaft position sensor, the FSM calls that a CKP.

Click to expand...

So lets see, accronym game time,.....CKP sensor must be "Cran Kshaft Position" sensor?:banghead: