Ok...and more...

[Sticks]

So, we've had this XJ for a little while now. Every now and then it feels like its on cruise control. If i put it into neutral the RPM's can race as high as 2K rpm. Give the accelerator a tap and it drops. Also, the tranny bucks sometimes. It's unpredictable. From a dead stop, just letting of the gas from mild acceleration...just bucks.

Allrighty, well a couple weeks ago, in typical Jeep fashion...I got a check engine light. Had it read, and forgive me for not recalling it, it pointed to a electrical problem in the transmission. Did some review online of the code and most forums pointed (and recommended) at changing the transmission pick up filter and the two quarts you lose from dropping the AW4 pan.

So, I did that. As much of a pain in the butt that was. The check engine light went out and seemed to drive ok. Now, I also did read that this could be, and probably is, a torque converter problem...as in, the torque converter is dying (or dead).

When I changed the filter, the merc 3 fluid did smell a bit and didn't have that rich red color. There was a good amount of sediment on the pan floor too.

We drove it to Wakefield last week (had no choice) after I had changed the filter and on the way back, it bucked pretty good one time and the check engine light came back on. The rest of the way home it would dance between 3rd gear and the lockup....RPMs just not settling down.

I want to change the torque converter but am afraid that I really just need to change the transmission completely.

Thoughts?

[4WDnRocksNmud]

pull the pan again and find out what color the oil is... it sounds like you have some definite gunk stuck in the valve body. How big are the sediment pieces this next go around? check your fluid levels... if the oil didn't smell quite right, and there was sediment, you could be burning up some of the oil, so your fluid is low. which would cause excess wear, which causes the sediment, etc etc...

[Sticks]

Levels are and have been where they should be. The color was more grey than red. There were no chunks of metal, only a very fine sediment...There was quite a lot of sediment, but it was all very fine and was more like a couple mils coating on the pan. Like, I didn't know that it was a coating on the pan till I grabbed it and it was on my fingers.

I also read a thread on a couple other threads and forums where people are chatting up about the lockup valve (?) possibly needing replaced...and problems with the CPS.

BTW, I hate this.

[87B2XLT]

The 'sediment' you're referring to sounds like the clutch plate friction material inside the gearset/clutch packs. Some is 'normal' per se, but sounds like you're going to need to drain completely, including the torque converter. That stuff will clog up things a little and eventually your transmission will give up the ghost. You may have a converter/pump going south as well.

Dave G

[Deleted]

The first thing everyone always says is to change the trans fluid. Let me ask you guys something, when was the last time you or anyone else you know successfully fixed a broken transmission by changing the fluid?

[Sticks]

+1 on changing just the fluid.

I don't know enough about the AW4 (or automatics in general) to say that I can even answer simple questions. I know that it feels like it's bouncing between lock up and third gear when hitting highway speeds.

The "driving" forward thing baffles me too...Karla has shown me that sometimes the entire jeep will speed up on its own to meet the 1500-2000 rpm demand that it sometimes goes through. Weird right?

Could it be the computer (too)?

[4WDnRocksNmud]

May 6, 2010 21:39:35 GMT -5 @fromme said:

The first thing everyone always says is to change the trans fluid. Let me ask you guys something, when was the last time you or anyone else you know successfully fixed a broken transmission by changing the fluid?

Me.

Next puzzler?

[jpeay]

get your trans flushed buy a shop I recommend Jay's transmission shop in Suffolk he does great work and is very reasonable

[Sticks]

if im going to drop the tranny, (with driveshafts, transfer case, linkages,etc)....just to change the fluid (right?)...I should probably consider just changing the torque converter and whatever this lockup valve thing is at the same time right? Plus flushing it...however that is accomplished?!?!?

***I see that the only way to flush it to take it somewhere where they can hook it up and run it while it draws fluid and flushes it out too.

Still $200+ for a torque converter. $30 to replace fluids.

Maybe I should rebuild it? Like $250 for a complete rebuild kit.

[4WDnRocksNmud]

if you rebuild it, you better make sure you have inch pound torque wrench, and a digital camera with lots of life...the valve body may have some gunk in it... it's that part, directly above the filter, when you pulled the filter off. Transmission flushes, i've never heard any good come of them... some of the sediment actually helps the tranny perform. If alllllll the gunk is gone, there's no buildup, so EVERYTHING moves freely, even the stuff that shouldn't.

[87B2XLT]

I am honestly not sure if the AW4 is controlled by the computer (it's a Jeep and I'm not as familiar as I'd like to be with anything past the last year of the CJs). Anyhow, that being said, do you know when the last time the fluid was completely drained and replaced along with the filter? If it's been more than 30-50k miles, then that's part of the problem. If it's holding fluid, then that leaves me to believe that the seals are not shot (crossing fingers), so it isn't probably ingesting any water or other foreign material. Going back to my first statement: Does the AW4 have an atmospheric vent? If not, then the 'sediment' is friction disk material from the transmission, which an excess of it means either the transmission is running at higher than normal temps or the converter/pump is not pumping adequately. The excess of the 'sediment' has possibly also caused abnormal wear / restrictions elsewhere in the transmission. A lot of things, including solenoid-operated-by computer things have o-rings on them. Going back again to my first statement: Does the AW4 have a vacuum modulator on it? That could also contribute to problems. That's about all my semi-educated guesses. If it were a Ford C4, C6 or any GM transmission other than the 700R and 200R and newer / pre-TH350 and Powerglide, I could pick it apart piece by piece... those are the only bona-fide, no bull transmissions I have worked on personally.

Dave G

[Sticks]

From my reasearch, it looks like if you have the time, couple special tools (extended snap ring pliers) and the bench space, it can be done. I don't know if I should just take the XJ off the road completely or if I should buy a working used one, and possibly rebuild that instead?

[87B2XLT]

It'd be easy if you have a spare transmission to rebuild then swap in, if in fact the transmission is going south. I forgot about something and re-read through this thread. Your transmission should be computer or module-controlled. Since it's 'a Chrysler'.... it would not surprise me if the control module is acting up. If you can find some sort of shop manual or info for diagnosing both the mechanical and electrical/electronic side of the thing, that might help. Could be a signal issue or could be a mechanical linkage issue - if it's shifting out of OD as you're going down the road and not giving it more skinny pedal. Given what we know so far, though, seems like the fluid has not been changed in a while if it doesn't look or smell normal. I would do a complete drain and refill and then take a look at the shift/kickdown linkages and also try and diagnose any possible electrical/electronic issues. I don't know if a diagnostic will pull what you'd need to know for sure (and the stealership's/shops charge a pretty penny to run one). If you can 'afford' to take the XJ off the road to figure out what's going on, then that probably would be a good idea.

Dave G

[jpeay]

If you can get to jays transmission he saved me an expensive rebuild he replaced a module $250 after two other shops told me it was going to be a $3000 rebuild

[gtmud]

From what I have read hear it sounds like the original Culprit is possibly the TPS sensor on the T-body. The TCU is not liking the signal from the TPS so it will cause harsh, or erratic shifting. I would replace the TPS sensor and get it set up correctly! The set up is VERY important but simple too. As far as your gunk in the pan, I have an AW4 in my 89, this XJ was ragged hard before I got it ( old hunting jeep) so the tranny saw Very hard times. I have been running that same tranny for 3 years now everyday to and from work, and of course wheeling, even went to GW with it loaded. The very first thing I did was flush it. About 3 times in about 4 month period to get all the old burnt fluid out. After the last flush I started using Lucas trans additive at every change, and have had no problems. Oh, when I first dropped the pan, I too thought I was in for a rebuild, but these trannys are near bullet proof, just as the old Ford C6. I would recommend a very good flush and then change the filter and run the Lucas additive, also get a really good tanny cooler on it. I have proved this out on my own, it very well might work for you and is far cheaper than a rebuild. If for some reason you need an AW4, I have one here out of an 90 XJ. Good luck.