Replacing differential cover gasket

Hello all,

A friend of mine has a 93 Astro Van w/ 84K on it, we did his rear brakes yesterday, and I noticed his rear differential cover was covered with oil. Not good. It's been 16yrs since I did one of these.

1) When replacing the gasket, is any gasket sealant required, or just the gasket itself?
2) How much oil to put in? I know there's a filler plug, but I don't know how to tell how much to add.
3) If anyone knows the kind of lubricant used, please tell. I know it's a heavy oil, but don't know the specs.

Thanks!

Hello all,

A friend of mine has a 93 Astro Van w/ 84K on it, we did his rear brakes yesterday, and I noticed his rear differential cover was covered with oil. Not good. It's been 16yrs since I did one of these.

1) When replacing the gasket, is any gasket sealant required, or just the gasket itself?
2) How much oil to put in? I know there's a filler plug, but I don't know how to tell how much to add.
3) If anyone knows the kind of lubricant used, please tell. I know it's a heavy oil, but don't know the specs.

Thanks!
I think the '93 Astro had the 8" rear end (same as an S10); regardless on your questions though;
1) a good gasket sealant is recommended, as the differential is leaking now, plus it has probably never been serviced, so the gasket will have to last another 80+k. Permatex's ultra black is spec'ed to GM OEM standard, but the ultra blue or ultra copper are just as good, if not superior to black (but black won't show as much)
2) this depends on whether your Astro is AWD, and if it had a New Process 207 or a 231 rear-end; either way it will take AT LEAST 5pints (2.5 quarts), and after the cover is on, just fill until the oil starts to weep from the filler plug opening.
3) an 80W90 or a 75W140 will do... depending on your driving and geographic location, AND if you are not planning on servicing it for another 80+K, I would spend the money on a synthetic and KNOW it will be lubricated at -40deg, or while flying down the freeway, gears whining at heating up to 150+...

hope this helps,
ctesla
ASE cert.instructor

It helps a lot, thanks for the details!!

A question: I've put synthetic in new vehicles, with good results. I've read that old seals, used to oil, will dry out and leak if synthetic is used. The article suggested semi-synthetic, to keep the old seals "oiled".
Thoughts?