96 Rear Differential Fluid

[1993Suburban]

Would it be ok to put Amsoil 75w-90 Synthetic Gear Oil in my rear differential? The book calls for 80w-90 but I can't find any synthetic in 80w-90 that isnt expensive GM fluid. Also I hear alot of people use Royal Purple 75w-90 without a problem. I am probably over-due for a rear fluid change, and I wanted to get the benifits of synthetic lubircation. The vehicle is a 1996 Suburban half ton, 350 engine, 4 wheel drive. Thanks!

[777stickman]

If it was me I'd spend the money and use what GM recommends. Your '96 probably has a lot of miles on it.

I think the synthetics are good if you switch over to them early and stick with it. Otherwise you should probably stay with the OEM stuff.

GM is always updating their lubricants and yes they are costly, but to me the cost vs problems from something different is nothing.

JMHO

[1993Suburban]

I tend to lean toward what you are saying. I have 155,000 miles on this rig (runs like a champ too). I switched over to Mobil 1 in my engine without problems. I seem to have developed a penny size oil leak, every week and a half, from the oilpan area probably (too cold to get under vehicles). Now that the synthetic has found this small hole (oil was quite dirty only after 2,000 on first change after switch), I hope that within time, it will clean and plump up the seal a little bit. This is wishful thinking, but it's a 12 year old 350 with 155,000 miles. Oil on the driveway comes standard. I know that the previous owner probably didn't flush out the rear end, so i figured i would before too long. Since purchasing this vehicle, I fill it with AC-Delco/Delphi/GM parts because I have heard too many horror stories, and also witnessed many problems from aftermarket stuff. I've had a few reccomendations on synthetic lubrication for the rear end, but never heard what weight and brand would be best suited. If anyone has any info on this, I would appreciate you sharing with me! Otherwise I suppose i'll just pick up some conventional from GM.

[j cAT]

Originally Posted by 1993Suburban

Would it be ok to put Amsoil 75w-90 Synthetic Gear Oil in my rear differential? The book calls for 80w-90 but I can't find any synthetic in 80w-90 that isnt expensive GM fluid. Also I hear alot of people use Royal Purple 75w-90 without a problem. I am probably over-due for a rear fluid change, and I wanted to get the benifits of synthetic lubircation. The vehicle is a 1996 Suburban half ton, 350 engine, 4 wheel drive. Thanks!

I believe the 80-90wt is all that is required in this application and spending more money for synthetic is of no added benifit. regular diff oil changes are required to remove debris generated. so if you are looking for longer trouble free operation replace this gear oil every 30,000mi or sooner if it begins to turn grayish........if this were a limited slip diff many have had problems changing to synthetic's .........