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1997 jeep XJ 120000 transmission will not shift when hot

Rob.viking

NAXJA Forum User
Location
TX
Transmission woes, 1997 4.0l XJ AW4 120000 miles

My wife was driving the jeep when she noticed a plume of white smoke coming out the back and then the jeep would not shift. The check gauges light came on and the heat was just above 210 with all other gauges ok.

After cooling down for about 30min waiting for me to arrive it operated ok for a couple miles before it lost the ability to shift. And the check gauges light came on. The motor would redline with no power transfer to the transmission.

At one point I pulled over and turned on and off the motor and it gained the ability to shift for a minute.

At idle when it has a rattle coming from the transmission that goes away when hot. I then called the tow truck and brought it home.

No check engine light. Fluid level ok, a little brown but not burned.

What are the most likely issues?

Some of my research suggest a torque converter? But this does not make total sense in my mind. Due to the fact it works when cold.

Unplugged the TCM and it will shift fine until hot and then behave as if in neutral no matter what gear.

What could it be?

Clogged filter

Torque converter?

Seems like low mileage for the tranny to fail

Thanks for the help.
 
The plume of white smoke is a good clue...
I do recall a symptom where trans oil can be sucked back up through a vac line. Been years since then. Unsure of any vac lines to the trans in an XJ but
 
I believe the white smoke was some fluid getting hot and bubbling out the breather tube. The motor runs clean.
 
Unplugged the TCM and it will shift fine until hot and then behave as if in neutral no matter what gear.

This would make me suspect that there is mechanical issue with transmission or possible a shift solenoid problem. The root cause of the symptoms requires diagnostics. The smoke only tells us that the transmission overheated and expelled fluid, or has a leak.


If you search Google, there is a complete Jeep Dealership AW-4 Service Manual you can download. It has all the necessary diagnostic and testing info, and repair info, you will need. A $ 7.95 genuine Jeep Service Manual from www.pacificcoastmanuals.com is also good to have.
 
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I have seen this on a tranny that was overfilled or had moisture in the fluid. When it got hot, the fluid got whipped up into a foam, screwing with the pressure and blowing it out the tranny vent tube and all over the exhaust.
 
I reviewed the service manual and it indicated a clogged filter could cause it not to shift. I dropped the pan and discovered a very filthy filter with a thick layer of fine metallic grit on the pan magnets. No shavings or other debris. Unfortunately the drain plug was stripped so I had to order a repair kit I need to install before I can see if this fixes the issue.

My guess is this is the first pan drop it has had.
 
I have seen this on a tranny that was overfilled or had moisture in the fluid. When it got hot, the fluid got whipped up into a foam, screwing with the pressure and blowing it out the tranny vent tube and all over the exhaust.




Check the coolant for oil contamination. If the trans fluid cooler in the radiator has a leak, you could be getting coolant into the transmission. Oil on the dipstick would have probably looked nasty too.


Otherwise, I'd say it's probably a mechanical failure. If the t/c is slipping badly it could cause it to overheat. Used AW4s aren't took hard to find, and you can look at https://www.naxja.org/forum/showthread.php?t=1053970 for swap info.
 
Problem solved!!

It looks like the clogged filter was indeed the issue. It may be too soon but the short test drive showed much improvement, the rattling noise is gone and it shifts much better.

I am very thankful she did not need a transmission.
 
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