Rear main seal

Good morning! It's been awhile since I've been on here. I researched the archives - -- - oh, btw, 'like the new site! - -- - and didn't exactly see what I was looking for so, I'll post it here.

I am aware of the other possible sources for what often looks like a leaking rear main - - - for the sake of this question, let's just assume it really is the rear main seal that's leaking, okay?

Back in August, I had my mechanic install a new rear main seal ('88 XJ Limited, 4.0L). After only a couple of days it was leaking a little and recently it is leaking as bad or maybe a little worse than it did with the old one. The XJ is back in there and he's working on it. He called Jeep and they questioned whether the seal he had installed was oem or aftermarket ...................................... well, my immediate and often reasonable assumption is they want to sell the exact same seal in a bag that says Jeep for 10x what the prefectly-good aftermarket one cost.

Here's the question. 'Any experience here that would convince or sway me that there really is something better about the oem rear main seal? [We're going with the oem seal now anyway, 'just cuz' - - but, 'wanted your input.]

Thanks for your thoughts and input.

Don

I know of nothing that would indicate the OEM is better than an aftermarket. Just for curiosity sake though, what kind of aftermarket was it? The most common cause I know for a replacement rear main seal leaking is improper installation, followed by damage to the crank where the seal covers it.

you sure its motor oil and not tranny fluid ?

Concur.

I've put in a few Fel-Pro rear mains, and haven't had any trouble afterwards. Granted, I'll put them in clean oil to soak before I start tearing things to bits, and I'm a little crankier about checking things than most, but that's just me.

I also tend to do all my own work - for this very reason.

5-90

Engine oil, not atf and no, I don't know the brand of aftermarket seal used originally. Don

I would lean more towards an installation error. I know when I was installing my new seal, I didn't hold it tight to the crank as I rotated it around the shaft, and the sharp edge of the engine block started to shave a sliver of rubber off of the outer edge of the seal. That's why all our friends here recommend buying two sets when you tackle this job, just in case.

Now that's the sort of thing I was suspecting! Don

I did my '88 with a seal I got from AZ for about $6 (I think). That was over a year ago and it's still fine.

Well, this wasn't as simple as I had expected. When the new seal came out, it was flattened-out - - - not bad installation nor a bad seal - - - a former just keep-it-running repair job.

Someone, before I owned it, was in there and apparently discovered some crankshaft wear. Instead of doing it right (turn the crank and install .010 under bearings), as I now must do, they put-in some .001 over bearings (hey, good news is, no pork rinds . . . ) and slapped it back together.

Consequently, the crankshaft bounces up and down a bit and flattens-out the rear main seal.

I guess I can't be too critical, it has been relatively leak free (for a Jeep) most of the time I've owned it.

Yes, one could argue my mechanic should have seen this last time . . . hey, this guy really treats me right and, without me even saying something, he will probably adjust the bill some himself and, if he doesn't this time, I likely owe him one - - great and honest guy!

Thanks for your input and, if I'm not "back" before then, everyone have a very Merry Christmas!

Don