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ZJ Transmission Help

1202 Views 19 Replies 13 Participants Last post by  papitt
Hello,

I just purchased a Jeep Grand Cherokee Laredo 4.0 three weeks ago from a private seller. It has 91k on the odometer, and the transmission was replaced 7 years ago at 81k. The owner kept this thing in his garage and daily drove something else, so it's in awesome shape cosmetically but I am having issues with it.

It stalls when on an incline, surges RPM when stopped in Drive, and shifts abnormally when going up hills, (2nd to 3rd, back to 2nd). I took it to a local mechanic to help diagnose the problem and he states "the transmission fluid looks almost brand new but the trans seems like it's slipping." Very discouraging, especially because they quoted a new trans installation for $2,500.

The dealership that initially replace the transmission said that the warranty expired in 2019, and that there's nothing they could do. Any advice on what to do?
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96 ZJ 4.0 / 42RE / NP242 / 4.56 Gears / HPD30 Truetrac / F8.8 Trac-Lok / 2x6 Sliders / Fully Skidded
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You don’t mention the year. 93-95 is OBDI and uses a separate TCM that is known to have issues and 96-98 is OBDII uses a single PCM and no TCM.
 

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I think you may have multiple issues. The trans shifting and the engine idling. I'd check for vacuum leaks and clean the ISV as well as checking the adjustment on TV (throttle variation) cable, as was stated above. That adjustment has a lot to do with down shifts and holding gears prperly.

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Shift cycling or hunting on these trannys are almost always a band or tv valve adjustment problem. More throttle valve pressure =more shift hysteresis = less hunting. If the bands are not adjusted correctly, the shifts don’t always time out right. A trans shop that does not recommend doing the external adjustments first can’t be trusted. These are OLD SCHOOL. Any tech with a half a brain should be able to sort it out without a rebuild.
 

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Discussion Starter · #10 ·
Shift cycling or hunting on these trannys are almost always a band or tv valve adjustment problem. More throttle valve pressure =more shift hysteresis = less hunting. If the bands are not adjusted correctly, the shifts don’t always time out right. A trans shop that does not recommend doing the external adjustments first can’t be trusted. These are OLD SCHOOL. Any tech with a half a brain should be able to sort it out without a rebuild.
I believe that the mechanic I took it to doesn't work on these often and immediately is jumping to a rebuild because it's the easiest thing to do. I'm going to look for a Jeep mechanic locally to see if I can find a more knowledgeable mechanic. The vacuum leak is most likely occurring, it is after all a 25 year old vehicle, but apart from youtube tutorials I am very unsure of locating the issue.
 

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I have got to say most automatic transmission shops don't really seem to have a clue on what they are actually doing. They disassemble the transmission, then reassemble with the cheapest rebuild kits, not measuring clutch pack clearances etc., and not using selective spacers and lock rings, don't replace "hard to replace" bushings, and generally doing sub par work - but charge premium price due to "amount of time it takes to properly rebuild an automatic transmission".
 

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TIMO_90XJ...
man how I agree with you. I worked for Chrysler for 10 years . TOTAL THIEVES as I saw it.
Fixed Right the 1st time . ONLY MENT Chrysler replaced every thing from the radiator cap to the right rear tail light bulb .
& BUT 99% OF WHAT WAS REPLACED WAS REALLY GOOD PART that didn't really need to be replaced.
 

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Stalling at a stop, surging, almost sounds like a torque converter not unlocking when at a stop, and then locking and unlocking during driving causing the surging. Fluid color typically wouldn't give you a clue about that issue, unless its done it long enough that its destroyed the clutches in the torque converter and the clutch material has circulated through the transmission but usually the transmission filter will catch that and you won't know for some time until you end up getting the stalling, surging of the tach even a minute amount can be a sign of the torque converter failing....they might have replaced the transmission, but depending on the shop, or the previous owner may have taken a cheap route and skipped replacing the torque converter which should be done if you replace the transmission anyways due to fluid and foreign material making its way through everything...to include the transmission cooler(s).
 

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How long has it been since the Jeep had a typical tuneup? An ignition issue can feel just like the trans is slipping.
 

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How long has it been since the Jeep had a typical tuneup? An ignition issue can feel just like the trans is slipping.
I have no idea, given the thing puking fluid all over the carport, its definitely a transmission issue, and the lower engine knock getting worse were great signs of get rid of it ASAP.

I think at some point I'll get another Jeep but maybe a WJ next time.
 

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Discussion Starter · #19 ·
How long has it been since the Jeep had a typical tuneup? An ignition issue can feel just like the trans is slipping.
I did a tuneup a few weeks ago with a new Distributor Cap and spark plugs. I've also replaced the IAC and have put in some injector cleaner to break up anything that's been sitting and might clog the fuel pump.
 

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KYLE. It's been a long time since I worked at CHRYSLER.. But I'm going to drop some more thoughts .
It honestly sounds like you've got a good Jeep to start with . You've just got to get past several different issues.
.1. when you tuned it up .. What spark plugs did you use. I SAY ONLY use Champion but I believe NGK May be the plug the Chrysler sells today. SORRY BUT DON'T put any other plug in that motor..
2. JEEPS ARE STUPID.... If it had at for a long time with a dead battery, Then it most likely need to go through a relearn feature. Meaning Crank it cold go drive it & make sure it warms up completely . Let it shift 1, 2, 3, 4th several times.
It's learning your foot habits in it's computer.. Take it home & let it cool down 100%. I Loaned one of mine out FOR LIKE 6 MONTHS ... He couldn't get it to run correctly . I kept telling him he needed to put a new battery on it. But He'd just jump it off & drive it home .
... SO IT LEFT HIM ONE to many times . He tells me where it setting . So I went & bought a new battery .. installed it..
& DROVE IT HOME . THEN I CRANKED it about 2 or 3 times a day & drove it around. In about a month .. It was running correctly. Now I'd put in 93 opt fuel & different fuel treatments . But IT FINALLY GOT TO RUNNING OK .
3. & I'M going to say at only 10K miles on the trans . It's not bad. '' GUESS'' ... BUT I would take it to a good trans shop &
A. Let them check it out.
B. I'd even have them change the filter & fluid completely. never hurts .
C. I'd ask them to adjust any cables it has.. &
D. It has a transducer & Governor Pressure Solenoid in it. If any thing indicates these 2 are bad .. Have them changed out.
We were one of the best Chrysler dealership TECH WISE IN THE Nation. We had 4 techs in the top 600 tech in the nation. THEY Sure liked to take the customers money but their vehicle was normally ''FIXED RIGHT THE 1ST TIME''.
E. & It does sound like there might be a Torque Convertor problem also . But that's a expensive fix so I'd sure want a good shop to check it out.
F. I've had about 4 techs work on my 95 V8 It sat for 5 years . The last little young kid just starting in his home back yard shop . He fixed a half dozen thing on this Jeep that others missed..
 
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