AW-4 slipping problem

Alright I’ve searched a million different threads and the answers are about as clear as mud. Sorry for the essay, but it’s a weird situation. So here it goes, I have a 93 XJ 4.0 3.5 RE lift, 4x4 np231, ford 8.8 rear and 4.10 gears. The other day I made a trip up the hill to do a little wheeling and shooting and the Jeep was having slippage issues in OD, it first started when I was driving to my buddies just on the highway but was minimal, when I got there I checked the fluid and it was a little low so I added some more. No issues until we started to get climbing in elevation. In OD the trans would slip right around the 2000-2500 RPM range, basically I would just lose power and RPM’s. If it was higher in RPM’s no problem, lower no problem only in that range. I kicked it down to third and it was fine. We got up there checked the fluid again still fine made it back down the mountain fine and right when we got in the city it started acting up again and pretty bad. Got it home checked the fluid still ok. It does not do it daily really only has happened when going on long drives in the heat on the highway. It did it a while ago only briefly and in part it was because I had too much fluid in there, at least that’s what I thought. I also read that the temp needs to be no more than 180* or the fluid starts to break down, so I went ahead and did a external trans cooler and that did help, but didn’t fix it. So now I’m thinking it’s because of the fluid I used. I had done nothing to the trans until I was working on my cooling system and replacing the radiator. Well the fine Jeep engineering of the stupid disconnects on the trans cooling lines proved to be well just stupid. After replacing the cooling system and I went on a road test and the bottom transmission cooling line popped off in turn spitting out all the trans fluid. I made it home but it was bone dry, I know I shouldn’t have drove it but literally if was only a few miles away and was late. The next I went to Advanced and the recommended fluid by them was ATF +4, so without thinking about it I went ahead and poured it in. After reading post after post about what fluid to use I’m thinking that I need to flush out all the ATF +4 and put in DEX III. Side bar the trans has probably 120,XXX miles on it, which I’ve read can influence which fluid to use. Two questions, first do I need flush out the ATF +4 and add in DEX or is it a separate issue? Second, if I do need to flush it what is the best way to do that? I was just going to run the engine, leave the trans in neutral and have it drain the fluid out while adding new fluid in until it runs red? Thanks

Dexron-Mercon III or equivalent, etc is what you should use. But I see several times where you were low on, or completely out of fluid. That means the bands got worn. You may still have some life in the trans, but honestly the bands are probably on their way out and you'll see it slipping more and more. Plus, you should change the fluid and filter, and use a can of trans flush to completely clean it out as well as the cooler and lines. I'd suggest putting some money aside for a future trans rebuild.

Thanks, CompleteCherokee. I was thinking the same about having to have the trans rebuilt I just didn't want to fork over a bunch of cash only to find out that maybe it just was the fluid. I had been reading about the aw4 rebuilds and I get mixed reviews some people say its ok to rebuild other say it's not worth it and just getting a spare trans with low miles and swapping that in. Any input in regards to that? The quote I got from my mechanic was about 700-1000 to rebuild it.

a rebuild is only as good as the parts used and the person doing the work. I have a trans shop here in GA that I've used exclusively for about 15+ years, and he's the only one I trust. Before that I had mixed experiences that weren't so good.

The aw4 is a pretty tough transmission, before I would shell out that kind of cash I would first do a full fluid swap to Dex Merc III. Next I would pick up a used aw4 from a you-pull-it junkyard, where I can personally smell the transmission fluid that is in the donor jeep (around me they are going for around 150). I am in agreement with Complete Cherokee that finding a transmission shop that does great work is often hard to find, and as such I personally would try to find a decent used one assembled by AW. Just my opinion.

I've used the guy for years and he's rebuilt engines and trannies for me with no issues. He actually rebuilt the engine on my current jeep and it's been great. Well first I will start with a fluid swap and then start looking for a used aw4. Thanks again for the input I appreciate it.

Valvoline Max Life Dex/Merc is great fluid. Try a gallon of that plus a bottle of lubegard red. My wife's Honda Odyssey uses both and we have 170k on it. The Honda has a crap trans, BTW.

make sure to swap the filter and use the flush in the lines to clear out any gunk in the trans, lines and cooler.

For flushing it out what is the best way to get all the old fluid out?

Unless you take it to a shop with a specialized pump, I believe the way most home mechanics do it (drain pan and fill) only gets out a percentage at a time. Then you drive a little bit and repeat.

I don't understand your explanation very well. You say you're losing RPMs and power. But if the tranny was slipping the RPMs should move up as you give it more throttle not down when in a gear. I would check to see your fuel pressure is up to specs. Drive the jeep with the fuel pressure gauge and see if it holds steady.

It has no filter, only a screen with no specified or recommended change interval from the manufacturer Do drain and fills with the proper fluid and it's the best you can do.

For the flush, they sell cans of trans flush at most autoparts stores. It connects to the cooling line ports and uses pressurized fluid to flush it out.

Here is a good write-up about changing the fluid and filter:
http://www.naxja.org/forum/showthread.php?t=1031061

note that in the OP's list, he had ft. lbs. instead of inch lbs.

If it is slipping the RPM's will go up, not down. Most times they slip in the lower gears anyway, at least in the beginning.

ATF 4 is supposed (re engineered) to work in the AW 4, I honestly can't tell you, but ATF 3 has given me issues in the past in the AW 4. I don't let the dealership mess with my fluid changes anymore, they screw it up on a regular basis.

Just having a problem at 2000-2500 hundred RPM sounds like a sensor issue. I've seen engines with bad O2 sensors buck at around 2000-2500 RPM. The sensor sends the wrong info and the PCM leans the motor out too much, it bogs and sometimes bucks. Usually only on a warm motor, at cruising speed 2000-2500 with a steady pedal or slightly accelerating. The O2 sensor leaning the motor out too much acts a lot like a tranny issues, that's what I thought the first time it happened to me.

I have seen questionable TPS function cause odd shift times (RPM's).

I'd do a key test for codes and see if you get any sensor codes.

I'd also do a TV cable adjustment. One of the first things to check when you have most any tranny issues.

Mercon Dexron seems to work just fine, Dexron 3 is likely the best choice. ATF 3 has given me issues on two different XJ's, I have no idea what ATF 4 will do.

Sounds like maybe you have some shift point issues and maybe it isn't dropping out of O.D. like it should and the engine is bogging down. Most times the OBD 1 and OBD 2 motors downshift too soon and not to late.

Sensor issue, TV cable adjustment, sticky O.D. solenoid?

I will check the O2 sensors that very well could be something also. It's goofy because it only does it if I'm driving on the highway for pro longed periods, about 30+ minutes or when I'm trying to get it up the hill. If I drive around town and am coming to stops and such it doesn't have issues. I get what you're saying about the RPM's should go up not down, but it didn't have issues until me having to add in the AW4 and that's when I started to think something drive line related. I can even drop it down into 3rd if it starts doing it and it's fine, only in OD does it get jittery. I will also check the TV cable and adjust it, it never seems to have issue with shifts points and for how it's geared rarely does it down shift to get more power.

that's weird that it only does it in OD at that specific RPM and after x amount of time. I'd think maybe it is a sensor issue, and adding the fluid was coincidental. Key codes would be good to check for immediately after it occurs again