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AW4 Lockup relay problem

89 XJeep

NAXJA Forum User
89 4L-6cyl AW4 203500 mi. Well maintained, gets 18-21mpg normally.

A couple of months ago I noticed the lockup was kicking in and out too much in the 35mph-45mph range while driving at a constant speed on very flat roads.

I took the Jeep to two former Chrysler, Jeep, Dodge transmission techs. We replaced the lock-up solonoid with an "after market" one. Every thing worked great for a week (couple of hundred miles.) Then one morning after warming up the torque converter no longer locked at all -- in any gear, at any speed.

There was no problem with the other gears and there was plenty of power delivered to the wheels.

This business of working until warm (10-20 miles) repeated every day. The Jeep had to THROUGHLY cool down (usually over night) before the lock-up would work.

The transmission tech used a scanner while I drove and said the scanner showed a signal was being sent to the lockup relay -- at least to where the scanner was connected. We replaced the solonoid with another one from the same supplier. (They have used this supplier for years and have not had problems with their stuff.)

This one worked perfectly for about a month (1200 miles) and then also begin to cease functioning after warm-up.

The tech does not think it is the solonoids but is not at all interested tracing problems.

Please help.
 
Wow, somewhat similar to my problem.

Tap into the gnd and signal lines from the transmission TPS with a digital voltmeter and record what you see. Of interest would be the value at idle, and the readings when it kicks in and out. The +V line to the TPS shold be recorded once too. It's easiest to tap into them at the TCU under the passenger side dash.

I have a similar problem, but it seems to be from a slightly shifting TPS reading. It's very senstitive.

Your can put something on the lockup signal line (+12=on) to see when it's engaged if you think it's getting the right signal, but not repsonding. Mine is doing everything it's told, it's just not being told properly... ;)

Report back - with your details, maybe I can combine with mine and we can figure this out. Please record to .01 or .02 v accuracy if possible.

Skip
 
If I can find a little time tomorrow I will try to hook up the volt meter and check the TPS voltages while driving. I have never done that before.

Since all real shifting (1-2, 3, D) is normal I have not been too concerned with the TPS. The tranny tech verified the settings with his scanner while driving before putting in the first solenoid and again before replacing it with the second.

Anyway this afternoon I discussed the problem with the owner of transmission shop that specializes in extensive, high-tech diagnostics. He said the non OEM lockup solenoid is probably the problem and to install an OEM before spending any money on diagnostic testing.

His shop does not warrenty any transmission with all but a very few specific aftermarket parts installed -- even if they are working.
 
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