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The Goblin 01-20-2020 07:56 PM

Transmission going crazy! 2002 Wrangler TJ.
Hey all. I'm brand new to the Jeep life and excited for the future adventures. I just purchased a 2002 Wrangler Sport with only about 78,000 miles. It's old, but overall in pretty good shape. It does have one pretty big concern though, the transmission is acting crazy when trying to shift into 3rd.

I have been searching the forums (this one and others), instructional sites, YouTube, etc. for a few days and haven't really seen anyone with the same problem (some similar, but not exactly the same).

It shifts fine from 1st to 2nd, but when it tries to shift into 3rd, it seems to shift back and forth 5-6 times as my speed picks up until it finally calms down around 45mph. All this happens around 1500-2000 rpms.

I adjusted the TV cable a little because at first it really seemed to be shifting SUPER early (like around 1000rpm), but that didn't seem to help. It takes a little longer to shift now, but it still bounces back and forth.

I just checked the transmission fluid and it is pretty dark and smells burnt. The level seems ok. I'm definitely going to change it.

Anyway, I could use some help if anyone has any suggestions. Could it be as easy as changing out the fluid? Any other thoughts?

Thank you all! I'm very excited to be a part of this great community! I am 42 and have wanted a Jeep since I was 16!

The Goblin 01-22-2020 04:19 PM

I had the fluid changed and put in a new transmission fluid filter. Didn't fix the problem. Still bounces back and forth between 2nd and 3rd gear until I reach about 50mph.

Any ideas?

mukluk 01-22-2020 06:42 PM

First thing that pops to mind would be a hunch that you have larger than stock tires but still have stock differential gearing, a surefire combination to have the governor valve in the transmission constantly kicking back and forth in response to throttle pressure and thus bouncing between 2nd and 3rd until the vehicle is up to speed.

The Goblin 01-23-2020 06:59 PM

Thank you mukluk! The jeep does have larger tires and they look almost brand new. The wheels look new as well. I wonder if the previous owner put the new wheels on and then sold it without changing the gearing. Is there any way to tell if the gearing has been changed?

Kruzin 01-23-2020 07:12 PM

Look here to determine what gear ratio you're running (use option 3 to determine if it's been changed) :

The Goblin 01-24-2020 01:34 PM


Originally Posted by Kruzin (Post 40855569)
Look here to determine what gear ratio you're running (use option 3 to determine if it's been changed) :

Thanks Kruzin. I really appreciate it. I will go get it up on jack stands and do some investigating.

At this point I'm trying to decide if it's better to have the gears changed, or to buy tires in the original size and go back to that.

I called our local 4x4 shop and they want about $2400 to change the gears. A new set of wheels and tires would be about $1600-1800 depending on the tire. So either way I'm spending a chunk of change. Any opinions on whether it's better to go one way or the other? Or is it just personal preference?

The Goblin 02-05-2020 02:41 PM

So I took it into the transmission guys and he was pretty sure its a stuck solenoid. Had him replace it and that helped quite a but, but didn't fully solve the issue. Now it does just fine for about the first 6-8 miles, but then it starts acting up again once things warm up. He checked a ton of different systems and said that they all checked out just fine, so his suggestion is that it's probably the computer.

Anyone have any experience with sending in a computer to have it fixed? Or is it just better to buy one that has been flashed and is ready to go?

jtec 02-05-2020 03:05 PM

Whoa - lets slow down on R&R PCM (computer) -
What causes him to suspect PCM? what tests, codes, are supporting that PCM has an issue?

POst the current tire size for the gang to think on, If you determine gear ratio let us know also.

mukluk 02-05-2020 03:24 PM

1 Attachment(s)
Your 2002 TJ has a 32RH transmission so the shifting is all controlled hydromechanically, not electrically by the PCM. The only interaction the PCM has on your trans is it controls the torque converter clutch lockup and that only happens in third gear above 35mph. In other words, step away from that mechanic.

Read through the TCC operation description from the FSM attached below and take note of the inputs the PCM uses to control the TCC lockup -- your oversize tires and stock gearing put a higher load on the engine, so your throttle position can easily vary back and forth over the threshold for your TCC to engage and disengage.

The Goblin 02-06-2020 12:04 PM

Whoa. Dang. The knowledge you guys have is truly awe inspiring to me. I can't tell you guys how much I appreciate the guidance. I'm not a total novice, but I'm by no means a mechanic, so I'm trying to learn as I go.

I must admit that this is frustrating because I took the Jeep to AAMCO, whom I thought were the experts on transmissions. So to hear that he obviously doesn't even know how these transmissions work is a little disheartening.

As far as tests go, he just said that he hooked up his scan tool and checked all the "systems" and everything was "working perfectly" (his words). His rationale for changing the computer was that he felt on Jeeps sometimes the different circuits and components on the circuit/mother board break loose from the solder and cause a bad connection so everything may look fine at rest, but once the vehicle gets up to speed any jarring on the road can mess the connections up. But, it sounds like from what you guys are saying, that this wouldn't really make sense because the transmission isn't really controlled electronically anyway.

He did say that it looks like someone has replaced (or at least messed with) the throttle positioning sensor, but it seemed to be working fine. Could that cause any concerns?

I went out and drove it today for about 15 miles. It's definitely better now, but it stills struggles. There were a few times when I got up to 3rd gear without any problems (under both light and heavy acceleration), but once I was out on the road for a bit, it pretty much happened every time after that. It's right about 35-40 mph when it starts bouncing back and forth.

I will get the tire size and post it and see if I can figure out the gear ratio as well.

Thanks guys!

mukluk 02-06-2020 12:43 PM

The speed range you're having issues is right at and slightly above the TCC engage/disengage threshold, so that may be what you're noticing. As I noted earlier the PCM uses information from the engine coolant temp sensor, vehicle speed sensor, and the throttle position sensor to determine when to engage or cut off the TCC, so the TPS can be a factor here -- but again I emphasize normal functioning of the TCC and the transmission shifting depends on the Jeep either being stock or that the gearing has been changed to accommodate an increase in tire size and keep the engine in its power band. Something that would help in addition to noting your tire size and figuring out what gear ratio you're running in the axles would be to pay attention to what gear the transmission is in and whether the TCC is engaged when the hunting issue occurs -- you should be able to notice a shift from first to second gear a little after taking off, then a shift to third gear as speed increases, then a drop of roughly 60rpm when the TCC engages at roughly 35mph with light throttle.

Your 32RH transmission is basically just a modernised version of the Chrysler TorqueFlite three speed transmission that's been around since the mid 1950s. Outside of checking the adjustment of cables/linkages and the bands, the main diagnostic testing that a transmission shop should be doing with that trans is to perform pressure checks at various test points to see if they fall in spec or not. Very little can be discerned from a scanner for these transmissions, unlike the later 42RLE (electronically-controlled) transmission used starting in 2003.

The Goblin 02-08-2020 03:22 PM

2 Attachment(s)
Ok. Thanks Mukluk and jtec. I drove it around the last few days and it definitely appears to be something to do with the TCC. Now that the AAMCO guys replaced the TCC solenoid, it seems to bounce around right at the 35mph mark. It's not every time now though, maybe 7 out 10 times, but I haven't been able to figure out why it seems to go ok when it does. I checked the tire size and what I am assuming is the gear ratio on the rear diff, this is what I found:

Tires: 33x10.50R15LT
Gear tag: 3.73

I haven't jacked it up and spun the tires/drive shaft to verify that gear ratio, but this was what was on the tag attached to the bolts so I'm assuming it's accurate (hopefully if someone changed the gears, they wouldn't have put that tag back on).

What do you guys think with those numbers?

Mukluk, knowing those numbers and what you posted about the PCM only controlling the TCC, do you think it would be worth it to try a new PCM and see if that solves the problem? I can order a remanufactured one and send it back free of charge if it doesn't fix the problem. I will be totally honest, I'm really hoping it isn't the gears because they are so darn expensive to change (so is putting on 5 new wheels/tires). But, I'm also realistic.

Thanks guys!

Kruzin 02-08-2020 03:28 PM

33s are too large for 3.73 gears, that's what your issue is. A PCM won't do anything for it. You should be running 4.11 gears minimum for that size tire.

mukluk 02-08-2020 04:01 PM

Your call if you want to throw a PCM at it, but I'd say the chance of that making any realistic difference is minimal at best.

The Goblin 02-08-2020 05:16 PM

Hmm. Ok. Thanks Kruzin and mukluk. Sounds like I have some decisions to make. I really really appreciate all the help you guys have given me. I can see how great of a community this is. I will keep you posted on what I decide.

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