Auto Tranny Problem

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OldVart

OldVart

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This is for a buddy who is having problems with an 87 Jeep Cherokee 4x4 Auto tranny, inline 6 cyl. This one has the Power / Comfort switch on the dash, although I don't think this has any effect on his current problem.
Anyhow, lately with the hot weather, he'll be driving along at road speed when the tranny will suddenly shift itself from OD into 3rd or maybe even 2nd gear and rev the motor in the 4K RPM range. When this happens, even if he puts the shifter in the N position, it stays stuck in the gear it self selected. Eventually it will shift back in to OD on its own.
I'm thinking it's really time for him to do the fluid / filter to start with, however, I also think there may be a servo or solenoid problem causing this.
All other the gears engage notmally, including reverse, the bands are not slipping in any gear, and the fluid level is correct with no burned look or smell.
Any ideas what might be causing this problem folks?
Thanks.
 
A service is the first place to start. Make sure he adjusts the bands also, not just a filter and fluid change. It's a good possibility that'll solve it. If not it's time for a rebuild.
 
Thanks fishy. I was thinking that would be the best place to start, but then I'm no auto tranny guru. :) I'll probably end up helping him do the work, so I'll be sure to adjust the bands.
 
Sid,

If it is an electronic shift tranny, you may want to check the lock-up servo. I had one get dirty and start to stick and it did some very similar things as you are describing and also gave me conv. shudder. If you are going to do the work, I would check all the servos.

Jack
 
Thanks for the info Jack. Actually, I was talking to my buddy last night and told him the next time it happened, to stop the vehicle as soon as he safely could, turn off the engine, wait a little while, then turn it back on again to see if maybe a sensor, servo, or the computer would reset itself. He is driving this thing on dusty gravel roads most of the time, and I was thinking maybe dust in one or more connections could be causing the problem. on a 22 year old Jeep, wiring connectors and such dry out and allow water and dust to get in there.
 
Good call Jack. I haven't done any electronic shift versions yet so I didn't think about the servo's. I remember you just went through that a few months ago.
 
I was taking with him last night and since he doesn't work today, I told him to take it in and have any engine and tranny codes pulled. If the engine or tranny threw a code, it will give us a starting point at least.
 
OldVart said:
I was taking with him last night and since he doesn't work today, I told him to take it in and have any engine and tranny codes pulled. If the engine or tranny threw a code, it will give us a starting point at least.
Click to expand...

Sounds like a good plan. Hopefully it threw a code to help.
 
If its an A500 or A518, the solenoid paks can short out (locks it in od/TC lock) or become open (downshift). If they have never been changed its a ***** since you have to take out the VB to change out the plug. Replacements are around $60 or so and have an additional plug on the harness at the solenoid pak so that future replacements don't require removal of VB. By the way, they are CHINESE made crap so be prepared. I know!! Brand new tranny and they failed after about 40 miles.....

Larry
 
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