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Mystery transmission leak

Scottwclark

New Member
Joined
Aug 26, 2020
Messages
1
Location
United States
Recently purchased 2002 Jeep TJ // 4.0L I6 // 32RH // 110k

I started with some basic leak chasing. Replaced the valve cover gasket and found the oil sender leaking.

I've got everything resolved and dry and decided to drop the AT pan and replace the filter.

Everything is great and leak-free. Seemingly randomly, the Jeep starts leaking AT fluid after being parked for about four days. It was a hot day, and earlier in the day, I had purposefully/obsessively checked for any leaks and found nothing, then an active dripping leak with a drop every 30min or so.

The leak is coming from behind the inspection cover, and the pan is dry. I check the AT fluid level, and it is very overfilled. That is confusing because I know I verified this level after the pan drop and filter change, which was completed a month ago.

Scratching my head, I decide to let the Jeep engine run to operating temp and shift the transmission into neutral and check the fluid level. I look under the Jeep, and there is a lot more fluid which leaked but isn't actively leaking now... maybe 3 oz. I check the AT fluid level... it's perfect.

I cleaned up all of the leak residue and let it sit for another couple of days. Another hot day comes, and the same scenario plays out... fluid level is high and AT fluid is leaking on the ground... there were no leaks between the two incidents.

Could it be a seal? How is the fluid level balance changing?
 

Gilaguy23

TJ Enthusiast
Joined
Sep 21, 2021
Messages
292
Location
A'holeville
A long shot here, but my first 93 Diesel 250/518 auto would allow the torque converter to drain out when it sat a couple days. IIRC it was a common issue on some Dc built auto's. Again, IIRC something about a check valve that sticks and allows everything back into the pan. One of the symptoms was if you fired it up and tried to drive off immediately it would not move until the converter filled and starter to do its thing.
 

Old_Crow

TJ Enthusiast
Joined
Dec 16, 2021
Messages
327
Location
Tom's Place, California
A long shot here, but my first 93 Diesel 250/518 auto would allow the torque converter to drain out when it sat a couple days. IIRC it was a common issue on some Dc built auto's. Again, IIRC something about a check valve that sticks and allows everything back into the pan. One of the symptoms was if you fired it up and tried to drive off immediately it would not move until the converter filled and starter to do its thing.
My wife had an old Plymouth Satellite that would do that. I knew what it was, and was gathering parts to fix it, but every time she'd park that thing in public, she'd come out and there'd be cards from 2 or 3 transmission shops tucked under the wiper blade. :)
 

hear

TJ Enthusiast
Supporting Member
Joined
Oct 18, 2020
Messages
949
Location
Prosper, TX
My initial thought is the selector seal, but the truth is it could be a lot of things. The best way I know of to track an ATF leak is to clean the entire thing with no leak residue. Then stuff paper towels around all the ports: NSS, TCC, cooler lines, dipstick tube, selector shaft...everything. Even stuff one up into the bottom part of the bell housing.. Let it sit, and then figure out which paper towels have red on them. Once you know for sure where the leak is you can go about solving it. That stuff has a tendency to run different directions and really mask the leak source.
 
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Rcroane

TJ Enthusiast
Joined
Jun 22, 2019
Messages
255
Location
Virginia
Could be coming from trans cooling lines. They can develop leaks at the crimped connectors or even pinholes in the line itself from corrosion.
 

hear

TJ Enthusiast
Supporting Member
Joined
Oct 18, 2020
Messages
949
Location
Prosper, TX
hells bells, I didn't notice that there are 7 posts total between the first two posters. We'll never see them again.