Gear oil.

[progress4m]

I planning to change gear oil (front, rear and trnser case) and I know that many people here have switched to 75W-90 gear oil. I would like to use synthetic, but it is not offered in recommended 80W-90, at least I cannot find it locally.
Can anyone comment if you noticed any negative effects (whining noise etc) from using lighter than recommended oil? Especially in the hot climates, like Texas.

Thanks in advance.

 

[skeetr1163]

I replaced all my fluids including the gear oil with Amsoil. Works great and should last a long time.

 

[skeetr1163]

I should have noted the type is Severe Gear 75W-90

 

[riverwolf]

I planning to change gear oil (front, rear and trnser case) and I know that many people here have switched to 75W-90 gear oil. I would like to use synthetic, but it is not offered in recommended 80W-90, at least I cannot find it locally.
Can anyone comment if you noticed any negative effects (whining noise etc) from using lighter than recommended oil? Especially in the hot climates, like Texas.

Thanks in advance.

In a multi-viscosity oil, the second number is the warm flow viscosity. Your 75W-90 and 80w-90 examples have the same viscosity on a warm flow test and theoretically the same heat protection (ignoring additives, base stock quality, etc.). The difference is the 75W will flow better in low temps...overall, a good thing, I would think.

I'm pretty sure you won't find a synthetic 80w-90 gear oil. Something about the nature of gear oil that dino can't be thinned out that much on the cold end.

Anecdotally, I swapped my diffs and xfer case to Mobil 75w-90 a couple of months ago and can't really say for sure I could find a difference with the OEM juice. The drivetrain might be a little quieter, but that could also be wishful thinking or a product of the drain-and-fill on the tranny at the same time (only 4 quarts out of 13).

-Brent

 

[progress4m]

In a multi-viscosity oil, the second number is the warm flow viscosity. Your 75W-90 and 80w-90 examples have the same viscosity on a warm flow test and theoretically the same heat protection (ignoring additives, base stock quality, etc.). The difference is the 75W will flow better in low temps...overall, a good thing, I would think. ...-Brent

Thanks for replies.
My concern was that before oil would get up in temperature would it provide enough protection being 75W versus 80W..?

 

[Top Shelf Synthetics]

I switched to Amsoil sever gear 75W-90, no problems at all. Made a noticable difference, rolls smoother and is quieter. Definitely recommend it!

 

[progress4m]

Thanks again, I will give Mobil 1 75W-90 a try… since it is readily available @ Autozone for $8.99 per q.
I will be going to Yellowstone in about three weeks. It will be around 3000 miles trip and will post results after I come back.