Posted by synoman on July 04, 01 at 05:52:06:
In Reply to: Gear Oil / Pinion Seal on Rear Differential posted by Greg in EP on July 03, 01 at 21:39:09:
Stay with a 75-90 or at most, 80-90 synthetic of a well known brand. The 85-140 is too high a viscosity for your application. The diff will love the lower viscosity, towing or not. Remember, GM calls for a 80-90, anyway. I would have the pinion seal replaced before installing synthetic in it. The synthetic has a much better flow ability and will seep past the leaky seal faster than dino oil. Replace the seal, it is not that difficult or expensive for a pro to do, either.
My thoughts.
synoman
: 96 ½ Ton Sub 4x4 – 3.73 rear end
: I want to change the rear differential oil to synthetic before I tow. Previous owner used regular 80/90 gear oil, but did very little towing. However, no paint left on the rear diff cover – due to heat I’m sure. A mechanic friend had same problem with his ‘99 Tahoe after towing a few times. He switched to synthetic 85/140 gear oil - no more problem. I have seen a lot of talk about using synthetic, but have not heard of many using 85/140. Seems like it would protect better on the hot end. Any problem with it?
: Also, has anyone ever changed a pinion seal on the rear differential? Mine is leaking a little. Don’t know if I should tackle it myself or take it to a shop.
: Thanks, Greg in EP (soon to be on vacation in LA)