1987 Chevy 3/4 ton truck

[wolfc70]

My BIL has a fully restored 1987 Chevy truck. It has 100k on it and he wants to change the diff fluids. The truck maybe gets 3k miles put on per year.

I was thinking of using Amsoil (I have a PC discount) severe gear and the Amsoil slip lock additive. He thinks switching to a syn will cause leaks. I do not think that leaks should be an issue since there are no signs of current leaks. I told him that the syn gear oil will help protect against rust better than conventional gear lube.

What do you guys think? Any personal experiences?

 

[Johnny]

Severe Gear 75W-110 would be an excellent choice for his truck. Are you sure you would need the additional slip lock additive?

 

[wolfc70]

Originally Posted By: Johnny
Severe Gear 75W-110 would be an excellent choice for his truck. Are you sure you would need the additional slip lock additive?


I am pretty sure it has some form of limited slip device. Won't really know until we take the covers off. Any worry about seals leaking? I know they shouldn't, but I have to convince my brother in law that synthetic will be ok to use.

 

[Johnny]

Well, they should not leak, but I guess anything is possible. The Amsoil product will do some cleaning. If in doubt and for no more than the truck will be used, just put in a good mineral 80W-90 and some GM LS additive if needed.

 

[mechtech2]

If a leak ever does occur for whatever, you will be the bad guy for your Amsoil advice. [Amsoil is a superior fluid, no doubt.]

With the projected usage, it should not matter what is in there -conventional or synthetic.

 

[FL_Rob]

3k per year? conventional,and if its condensation causing rust you're concerned about Amsiol would suffer that result as well, save the money or put it toward one of those neat diff covers with a built in drain plug .