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?

 

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.

 

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?

 

Look here to determine what gear ratio you're running (use option 3 to determine if it's been changed) :
https://www.jeepforum.com/forum/f9/faq-how-do-i-determine-my-gear-ratio-615380/

 

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?

 

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?

 

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.

 

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.

 

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!

 

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.

 

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.

Might be time to do hydraulic pressure & air checks.

 

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!

 

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.

 

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.

 

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.

 

What do you guys think would be an adequate tire size? I found a guy who is selling his original wheels with tires for cheap (all 5) from a 2014 JKU that are P255/75R17, but those aren't really much smaller in total diameter (about 32") so I'm not sure how much smaller I need to go to be ok with my 3.73 gears.

 

Those rims won't work for your TJ, they changed the bolt pattern with the JKs from 5x4.5 to 5x5.

 

Oh that's good to know. Was it just the JKs? Or should I stick to TJ wheels only?

I'm having a hard time figuring out what tire sizes would be ok with the 3.73 gears. All the charts I'm looking at are for manual transmissions and not for automatics.

 

Actually just found some info on a Quadratec site that answers the bolt pattern question. Looks like YJs and TJs share the same patterns/sizes (along with a few other non-wrangler Jeeps). Thanks Kruzin.

 

Well, I've decided to just get the gears changed. I ended up getting my local off-road shop to give me a pretty good deal by matching some labor and parts quotes I got from other shops. Going to do Yukon gears, 4.56 ratio. It's heading in next Monday and Tuesday! Wish me luck!

 

Well guys I need your help again. I picked up the Jeep today after getting the gears changed, and it is STILL doing the darn transmission chugging thing!

It seems like it is a little better, but that may just be my own wishful thinking. So, after changing the gearing to 4.56, it still lurches between 1500 and 2000 RPMs. I'm very frustrated with the shop because the guy at the desk I've been working with didn't even tell the technician about the lurching or to try and diagnose the issue! He just told them to change the gears. No one even drove the Jeep after they were done! And this is supposed to be the big time off-road shop in town.

So, any suggestions now? Any ideas what to check now that the gears are changed and it didn't solve the problem?

 

I'm not really buying the fuel filter theory due to how large the filter is (it would take quite a lot to clog it), and one would expect a filter issue to cause problems at high engine revs due to restricting the flow, not at low-medium revs like your case.

Engine coolant temp plays a role in the PCM's TCC application strategy partly due to managing the load on the engine during warmup, normal operations, and overheat conditions, but also in large part due to the fact your transmission fluid cooler is contained within the stock radiator. As such, heat from the engine coolant can and will affect the temperature of the transmission fluid, and fluid temp/viscosity has an effect upon how the transmission shifts.

 

Ah, ok. So the coolant does play a part in the TCC functionality, that's quite interesting. Thanks mukluk. I was looking through all the papers that were stuffed in the glove box and I found receipts for a new PCM and throttle position sensor that look like they were installed last fall. Do you think anything could have gone wrong with replacing either of those things? Since they are both related in one way or another to the TCC? Like adjustments that may need to be made and weren't, or wrong brand or something like that?

I ask about brand because I had to change an o2 sensor and I kept reading how Bosch sensors throw codes in Wranglers, and the sensor I replaced actually looked quite new; so I wonder if a Bosch was put in it last time it was replaced. So I replaced it with the recommended brand (NTX? Something like that?) and the code went away no problem. Anyway, just a thought. Trying to cover any option I can think of before I take it into the shop again to have the pressure tested like you recommended.

Also, I'm pretty sure the dealership said they replaced a cam sensor before I bought it. Those are all the repairs I know about.

I'm learning a ton with this. Thanks!

 

... a new PCM and throttle position sensor that look like they were installed last fall. Do you think anything could have gone wrong with replacing either of those things?

Possibly, but not very likely in my opinion. You can test the TPS fairly easily with a voltmeter if you suspect something may be wrong with it: with the ignition on and engine not running back probe the wires running into the TPS connector, see that you have roughly 5v at the OR power wire, then check the voltage on the OR/DB signal wire at idle and while you slowly open the throttle to WOT; the voltage should go from roughly 0.26v at idle and smoothly transition up to roughly 4.49v at WOT.

It's a bit of a Hail Mary, but to eliminate the possibility of some minor gremlin causing this issue you could spend some time under the hood and transmission cleaning and tightening electrical connections as well as checking for vacuum leaks. That would cost no more than a bit of your time and a can or two of sensor-safe spray cleaner.

 

Ok, thanks. I replaced some vacuum hoses a few weeks ago, had some pretty large leaks, but I think I got them taken care of.

I went out and drove it around quite a bit yesterday and I actually had NO lurching for the first 6-8 miles or so. I thought it had actually gone away. But, as I turned around and headed home, it started again. All this under very light acceleration because I'm still breaking in the new gears.

So here is a thought that I would really like your opinion on: I have been dealing with two major problems on this Jeep and, until last night, I thought they were separate problems that were unrelated, but last night it occurred to me that maybe they actually are quite closely related. The other problem I'm dealing with is that I think I have a cracked flex plate. I hear the typical clanking sound coming from the flex plate/oil pan area and I have tightened the torque converter bolts, so I know it isn't them. So, could a cracked flex plate affect the torque converter? Since they are literally bolted together? If the flex plate is cracked and not functioning properly, could that keep the torque converter clutch from being able to engage properly? It would make sense to me that if the plate is cracked and flexing too much that that would alter the way the torque converter spins and engages with the clutch. Also, it would make sense that it settles down as speed increases because the flex plate would be spinning with so much speed and force that the effects of a crack would be minimized.

I may be totally off, but as I'm learning about these various components, it suddenly seemed like these two problems may be one in the same.

Thoughts?

Thanks SO much for your help and advice!

 

I highly doubt a cracked flex plate would cause the TCC troubles, especially so if you're not getting any fault codes.

Regarding your noise video in the other thread, it sounds like piston slap or lifter noise to me. A cracked flex plate tends to be a sharper ticking noise.

 

Ok, lol, well it was a thought anyway.

Thanks mukluk! I really appreciate your assistance. Sounds like the pressure tests you recommended are the next step then I think. I found a copy of the FSM and it recommended air pressure tests for TCC problems as well. I have a shop that I trust more than the AAMCO guys, they replaced the engine in my Volvo and were one of the only shops who would even touch it. They are a little more expensive, but they are very very thorough, so I think it's time for me to take it in to them.

You saw the video in the other thread huh? Don't think it's a flex plate? That's good to know. I guess if it's just piston slap then that's something I can live with. It's just weird that I can't hear anything from the top end, only underneath near the oil pan/bell housing. I used a stethoscope and the bottom of the engine and the bell housing was where I could hear the noise most clearly.

On to the next step then. Thanks again! I will keep you posted.