Transmission leak

bmcgc

bmcgc

TJ Enthusiast
Joined
Dec 13, 2023
Messages
424
Location
Georgia
The first couple months I owned my 99 Tj 4.0/AT, all was well. The last few months I have had a giant transmission leak. So big, that I have had to add fluid. We have only driven it a couple times since late April, so the leak has been on the back burner.

This weekend I am going to attempt to drop the skid plate for a look. If I get the plate off, I am going to hit it with degreaser and the pressure washer. Any guesses on the likely source of a large leak? From what I can see, it does not appear to be coming from the pan.

I've got a 65 Mustang, 67 Mustang, Class A motorhome, Jeep, 2 dogs, a lawn to mow and a wife. I can't keep up.
 
On my TJ, I've had 2 transmission leaks. The first was the output shaft seal of the transmission. There is a weep hole at the back of the transmission. If the fluid is coming from there, it is probably the output shaft seal. If you are going to replace that, also replace the input shaft seal of the transfer case since you'll have to take the TC off to get to the trans output shaft seal.

I've also had the shift shaft seal leak. I replaced it last November, and unfortunately, it is leaking again for me. You can diagnose that fairly easy by cleaning up the area by the shift shaft seal really well, wrapping a paper towel or blue shop towel around it, wait overnight, and check for red fluid on it the next day.

Also, this may sound dumb, but get some anti fungal powder spray to help diagnose the leaks. After you get everything cleaned up, let it dry, and then spray the white powder everywhere. The leaking red trans fluid will really show up then.

Have you taken off the skid plate before?

Also, if you are able to figure out where the leak is coming from, reply to me directly and I can give you some more advice.
 
bmcgc said:
The first couple months I owned my 99 Tj 4.0/AT, all was well. The last few months I have had a giant transmission leak. So big, that I have had to add fluid. We have only driven it a couple times since late April, so the leak has been on the back burner.

This weekend I am going to attempt to drop the skid plate for a look. If I get the plate off, I am going to hit it with degreaser and the pressure washer. Any guesses on the likely source of a large leak? From what I can see, it does not appear to be coming from the pan.

I've got a 65 Mustang, 67 Mustang, Class A motorhome, Jeep, 2 dogs, a lawn to mow and a wife. I can't keep up.
Click to expand...

You didn't list kids, which would trump all of those in one. There's hope.

Are your vents plugged? If the PCV on the motor fails or vent on an axle/gearbox gets plugged, there's no way for built up pressure (from heat) to escape. This causes it to find the path of least resistance, which is usually not in our favor. This can be in the form of a pinion seal, trans input or output seal, diff cover seal, rear main seal, etc.

A trans pan is the easiest, and gives you an excuse to do a fluid change.
 
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