TC Gremilin 96XJ

[fishinpolejoe]

Hello everyone.

New member here, although I've been coming here since March for info on the XJ I bought. It's a 96 4.0 HO, 4 door, 4wd, 274,000 miles. The guy I bought it from said he had put "another transmission", which I assumed to mean a used one, in it at 200,000 miles. I've researched TC issues from the archives here quite extensively and have learned about the many possible causes. I'm hoping someone might be able to point me in the right direction with my TC issues based on the information I can provide.

My XJ had 253,000 miles on it when I bought it. I made some minor repairs to it and it runs great and drives great. After a few months and eight or nine thousand miles (I deliver pizza), I noticed that every now and then, I wouldn't get that final 'shift' where the TC would engage and allow the XJ to cruise at a low RPM. The RPM's would stay at 2,100/2,200 at 55mph on level ground when it should be running at 1,750 or so RPM's. Try to climb a hill and the RPM's go even more unusually high just to maintain the speed limit.

I didn't think much of it at first. It would happen on one occasion and not happen again for maybe weeks. Then it started to happen more often and with greater duration. Sometimes the TC wouldn't work for most of the day and then mysteriously kick in, sometimes it wouldn't work for days at a time and then work for a week. It seems to be pretty much unpredictable.

Most recently, for a week I drove to work. I would pull out of my driveway with a cold engine, accelerate to 55mph, the TC would engage, and the RPMs would drop to 1,750. A half mile out of my driveway I let off the gas to go around a curve. When I get back in the gas, the XJ cruises at 2,100 RPM at 55mph, and the TC would continue to not work until parked over night again. After that week, the TC works perfectly for three and a half days, goes out for the better part of one pizza delivery, then mysteriously starts working again.

The things I have noticed that have any consistency is that the TC always seems to work when you first start it after it sits over night. Also, it always seems to stop working after going down or up a steep incline, and/or after letting off the gas completely.

I want to think it is due to a sticking solenoid. What do you guys think?

I thought about trying some TF additive for shits and giggles.

Joe

 

[8Mud]

I'd start with the easy stuff first, TV cable adjustment, then check the CEL codes.

96 is pretty notorious for wanting to downshift early. It seems to be in the programming. If the TV cable is out of adjustment and/or the TPS is a little off it can aggravate the whole situation.

I know I have to back off the gas pedal a little to get mine to upshift sometimes, I suspect my TPS is flaky, but not flaky enough to leave a CEL trouble code.

My early downshifts improved maybe 50% after a TV cable adjustment, being just one click off can make a big difference.

Could be a sticky, high or low resistance solenoid, but check the easy stuff first.

 

[fishinpolejoe]

I'd start with the easy stuff first, TV cable adjustment, then check the CEL codes.

96 is pretty notorious for wanting to downshift early.QUOTE]

I'm experiencing early downshifts. This is my first Jeep, so I didn't know if they were designed to downshift early or what, but it seems to downshift unnecessarily to me. You can't let off the gas or almost all the way off of the gas going around a curve without the TC disengaging or without a 4 to 3 shift at lower speeds on back roads. When the TC is working though, I can maintain 4th gear at 35 mph up a hill at 1,100 rpm!

My first thought was that the TV cable could need adjusted, but a mechanic friend of mine told me that mine wasn't adjustable. This gives me new hope.

I haven't had it to the garage to have it scanned because I never can predict when it will work and when it won't. If it isn't malfunctioning when I have it scanned, there will be no code, of course.

 

[fishinpolejoe]

I would also like to add that when the TC isn't engaging, the RPM's will still drop to 1,200 or so at 55mph when you are going down a hill and you let completely off the gas. The RPMs will fluctuate at constant speeds on consistent downgrades which also seems odd to me. I'm no gear head and I've never paid this close attention to my tach/tranny so bear with me.

 

[8Mud]

Some codes will set into your onboard computer (PCM), some will light up the CEL (check engine lamp), some codes won't illuminate the CEL but will be stored for retrieval either by using the key methode or a scan tool. You don't have to catch it in the act to have a code, depends on what is causing your issues.

Just a guess, but if your speed sensor is completely bad the CEL will illuminate. A OBD 2 code scan may show a flaky speed sensor. Pretty much the same with a TPS.

The first step is most always to check the grounds before you move on to more exotic solutions. Poor grounds can cause all sorts of mischief. And check the fluid levels, remember the tranny gets check hot and with the motor running, you likely know this, just saying.

I usually disconnect the battery for awhile and reconnect it, then take it for a drive and see what happens. Don't let it sit and idle after disconnecting the battery. There is a relearn scenario in the book for the PCM/TCU. I've found a combination of highway driving and some stop and go to work just as well as the relearn sequence. One thing about disconnecting the battery and reconnecting, try not to arch or wiggle the clamps, smooth on and smooth off.

And like I said, I often have to back off the gas a little to get an upshift, especially if I'm going up a gradual hill. A lot of people have complained about this and the tranny dropping prematurely into passing gear (downshifting early). Many of the complaints were 96 models, seems to be a combination of a glitchy TCU (transmission Control Unit) program and maybe the tranny pressures TV cable adjustment, maybe a combination of both. I've learned to live with it.

The coast function is RPM dependant if I remember correctly. You may be just at the RPM range it is trying to go into coast mode (supposed to save fuel and lower emissions). You may have an issue or it may just be the nature of the beast. I do have to say though, mine coasts and compression brakes well, with no noticeable fluctuations or glitches. I just get kind of random upshifts and downshifts depending on throttle location (how hard I'm accelerating). In other words there seems to be a fairly large RPM range when it decides to upshift. It's always been that way for my 96, I just got used to it. When I get a late shift or it isn't shifting when I think it should, I back off the throttle a little, let it shift, then resume accelerating moderately, works for me.

 

[minionsram]

I'd start with the easy stuff first, TV cable adjustment, then check the CEL codes.

96 is pretty notorious for wanting to downshift early.QUOTE]

I'm experiencing early downshifts. This is my first Jeep, so I didn't know if they were designed to downshift early or what, but it seems to downshift unnecessarily to me. You can't let off the gas or almost all the way off of the gas going around a curve without the TC disengaging or without a 4 to 3 shift at lower speeds on back roads. When the TC is working though, I can maintain 4th gear at 35 mph up a hill at 1,100 rpm!

My first thought was that the TV cable could need adjusted, but a mechanic friend of mine told me that mine wasn't adjustable. This gives me new hope.

I haven't had it to the garage to have it scanned because I never can predict when it will work and when it won't. If it isn't malfunctioning when I have it scanned, there will be no code, of course.

the cable is adjustable.
Shift transmission into Park, shut engine off and raise hood.
Press cable release button
Push cable conduit back into cable sheath as far as possible
Rotate lever on throttle body to wide open throttle position. Cable will ratchet to correct adjustment point as lever is rotated

 

[tetrad]

What does your fluid look/smell like, and is it at the right level?

You'll want to check it at a hot idle, in Neutral. I believe the procedure is to park it, set the parking brake, put it in neutral, take out the dipstick and wipe it off and set it aside, run through all your gears from park to D and then back to Neutral, and then take the reading by feeding the dipstick back in and pulling it out.

A quick drain + fill can be done in about 15 minutes without removing the oil pan -- the only tricky part is getting the fluid back at the right level. If it is low you'll have slipping and poor/delayed shifts. If it is high you'll have similar symptoms, and when it gets hot it can bubble over and hit your exhaust and smoke.

 

[fishinpolejoe]

Thanks for all the great information!

Update:
My TC functioned flawlessly after posting this until last Sunday. While delivering pizzas on Sunday, the TC would not engage on several brief occasions, on several different trips, but worked for the most part. I noticed that when it didn't want to work, I could give the throttle an extra nudge and usually it would engage.

I drove to work (eight miles) Monday and the TC stopped working after climbing a good sized hill. It continued not to work at all on all my deliveries that night (I drove about 130 miles). I parked it at the end of the night for an hour and a half while I closed the store. I left work and the TC worked for about a mile and a half. I descended the same good sized hill and the TC wasn't working when I got to the bottom. After another mile and a half I turned onto a 35mph speed limit side road for a mile or two and then back onto the highway. When I got it back up to 60mph, the TC started working again! I'm baffled. I haven't driven it since then.

My transmission fluid isn't burnt or low. I've had my XJ serviced seven times since March and the mechanic always checks the tranny fluid level to make sure it is full and not burned. I stand right there in the garage and watch him do it. I also check the fluid myself between oil changes.

I've never had a CEL light except for when I disconnected the temp sensor.

Whatever is causing the problem isn't causing it all the time. If the TV cable needed adjustment, I would think that I would be having the problem all the time. Perhaps it is like 8mud said, a flaky speed sensor or something similar.

I'm hoping to get a constant failure of the TC at a time when I can disconnect the battery and go through the relearn process to see if that helps. Does anyone know how long the battery needs to be disconnected?

 

[tetrad]

To clear the PCM adaptive memory: (From CJ7-Tim's post on http://www.jeepforum.com/forum/f11/best-correct-method-reset-ecm-548305/)

Disconnect the POSITIVE battery Terminal clamp and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory).

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”

(It will take roughly 50 full warm-up cycles to relearn).

--

You might also try experimenting with unplugging your main TCM connector. This will put the AW4 in manual shift mode. 1-2 is 1st gear, you have no 2nd, 3 is 3rd gear, 4 is OD. You might be able to get a better picture of what's going on for TC vs shifting.

 

[fishinpolejoe]

Any chance this could be caused by a bad set of plugs and wires? I've noticed that my plug wires are missing insulation where rats have chewed on them. I've wondered if the TC isn't engaging due to a lack of power from the bad wires, although it will pull steep inclines with ease at very low RPM's

I also think about what 8mud said about grounds. When I got my XJ, it smelled horribly of rat urine. I removed the seats and carpet and found three rat nests. They chewed some of the seat belts in half, ate the padding off the door handles, even chewed the rubber cover off the shifter. When I replaced my blower motor, it's wires were almost completely bare and touching the body! I imagine there is more damage I haven't found yet. In my experience, electrical problems increase with wet weather. My TC functioned perfectly through several days of rain and snow, so I'm not sure if that could be the problem.

 

[8Mud]

Had a thought, my middle daughter is a two footed driver, one foot for the brake and the other for the gas pedal. She had a tendency to ride the brake pedal a little, the RPM's would fluctuate as the brake switch engaged and disengaged and the torque converter locked and unlocked. Took me awhile to figure out what she was doing.

Is it possible you have a sloppy brake pedal that isn't completely releasing the brake switch? Maybe the brake switch is flaky, weak, sticky or adjusted to close/tight?

I had a Weasel that chewed up the engine bay wiring in my wifes first XJ, what a mess. Nothing smells quite so foul as Weasel feces.

 

[fishinpolejoe]

Had a thought, my middle daughter is a two footed driver, one foot for the brake and the other for the gas pedal. She had a tendency to ride the brake pedal a little, the RPM's would fluctuate as the brake switch engaged and disengaged and the torque converter locked and unlocked. Took me awhile to figure out what she was doing.

Is it possible you have a sloppy brake pedal that isn't completely releasing the brake switch? Maybe the brake switch is flaky, weak, sticky or adjusted to close/tight?

I had a Weasel that chewed up the engine bay wiring in my wifes first XJ, what a mess. Nothing smells quite so foul as Weasel feces.

I considered that as well after reading about someone else's trouble here. I've tried playing with the brake pedal while driving in an attempt to get the TC to engage. Tapping the brake, pulling up on it from underneath the pad. That never helped. I've paid attention to the brake light in the mirror and it always responds properly to the brake pedal. I'm not sure if I can rely on the light to indicate that the TC is also getting the correct signal though. I have noticed that it doesn't coast the same as other vehicles I've had. Hills that I used to have to brake on in my 2wd S-10 (similar in weight to the XJ) I don't have to brake in my Jeep. When I'm going between 30-40 mph and let off the gas, it often instantly downshifts and compression brakes pretty hard for a brief moment without me touching the brake. That seems odd to me.

I took it out earlier and again, after climbing the steep incline at 55mph/1,800rpms, I topped the hill, let off the gas as I was going down hill very briefly, leveled out and I had to push the rpms to 2200 to maintain 55mph on level ground. Perhaps it has something to do with changes in the pressure in the tranny?

 

[fishinpolejoe]

I should also add that I live in a mountainous area. The roads are full of curves and hills so the tranny gets a serious workout. Especially driving 100 + miles per day for my job. I make a lot of 15 - 30 mile round trips in one night at work which means a lot of heating up and cooling down. I ask a lot from my XJ and it does a damn good job for the most part.

 

[fishinpolejoe]

I've cleared the PCM as tetrad suggested and adjusted the TV cable as well. Nothing has changed. I had some trouble with the cable release button. Once I got it pushed down enough, I thought I'd never get it to come back up and catch the cable. Plenty of WD-40 and a lot of thumb work got it moving again. I may try it again tomorrow in the daylight just to make sure I did it right. Then it's off to the mechanic for a scan I suppose. I'm still tempted to try a fluid additive.

 

[tetrad]

I've cleared the PCM as tetrad suggested and adjusted the TV cable as well. Nothing has changed. I had some trouble with the cable release button. Once I got it pushed down enough, I thought I'd never get it to come back up and catch the cable. Plenty of WD-40 and a lot of thumb work got it moving again. I may try it again tomorrow in the daylight just to make sure I did it right. Then it's off to the mechanic for a scan I suppose. I'm still tempted to try a fluid additive.

Well, you're about hitting the limit of my AW4 diagnostic ability. Try adjusting that TV an eight of an inch or so on either side of where it auto-ratchets. You should notice different downshifting behavior.

I would be extremely hesitant to put any kind of additive in my AW4 except as a last-ditch "work until I can swap it out" solution. It sounds like in general your trans is strong, ie not slipping etc, so I wouldn't add anything but clean DEXMERC -- if you want to try it that's up to you.

If your TV cable is working properly, and your fluid is good, and your trans just doesn't want to upshift, that could be a bad solenoid, or some kind of blockage in the valve body, or I don't know what else. I still recommend a manual shifting test -- if you are in third, and pop it up to OD, and it takes 8 seconds to engage, you have some data to start analyzing the problem. If the computer does it, you don't know when it tried, just when it succeeded.

You could have your mechanic hook a pressure gauge up to the pressure test port. Here is a detailed list of tests and symptoms (kudos to 5-90 for supplying these):

--

Hydraulic Pressure Testing
(pressure test port on P/S of case, above NSS. It's some oddball metric thread I've not identified yet...)
Range D at idle 53-61psia
Range D at WOT 161-196psia
Range R at idle 73-87psa
Range R at WOT 223-273psia
Note: psia(pounds per sqare inch absolute = psig +14.7 psi @ sea level.)

Symptomology:
High pressures in D & R, check:
Line Pressure Cable
Throttle Valve, Downshift Plug, or Throttle Cam
Primarly Regulator Valve Sticking

Low pressures in D & R, check above AND:
Front Pump Gears and Housing
Overdrive Clutch

Low pressure in D only, check:
Forward Clutch
Fluid Leakage in "D" Range Circuit

Low pressure in R only, check:
Shift Linkage/Manual Valve Adjustment
Fluid Leakage in "R" range circuit
Direct Clutch
First/Reverse Brake


Stall Speed Test:
With engine running and parking AND service brake engaged:
Shift into D range, rev engine, and note peak RPM on tach - should be 2100-2400.
Shift into R range, rev engine, and note peak RPM on tach - should be 2100-2400.
Stall converter NOT MORE THAN 4-5 seconds, and allow fluid to cool beween tests. (ie let it run a least 30-60s in neutral to circulate fluid)

Symptomology:
Low Stall Speeds in D & R:
Low Engine Performance
Stator Clutch Slipping if stall speed less than 1500RPM

High Stall Speed in D:
Low Line Pressure
Forward Clutch Slipping
One-Way clutch #2 slipping

High Stall Speed in R:
Low Line Pressure
Direct Clutch Slipping
First/Reverse Brake Slipping
Overdrive one-way clutch slipping

High Stall Speeds in D & R:
Low Fluid Level
Low Line Pressure
Overdrive One-Way Clutch slipping