Gear oil

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Jun 18, 2019 | 02:51 PM

caravaggio2000

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Gear oil

Probably a stupid question...

I figured now was a good time to suck the old gear oil out of the rear and replace. Who knows if it has ever had a change. My reading says 90w is what I need, but... none of the local parts stores had it.

I picked up 85w-140 Valvoline gear oil (not synthetic). Am I good to go?

Jun 18, 2019 | 04:36 PM

1TonBasecamp

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From: San Jose, CA

Maybe, maybe not.
Most have gotten away from the lube that was common 40 years ago when our trucks were still relatively new, but the multi-vis lubes have all that they had and more going on. So I'm a fan...

I'm also a fan of the slightly thinner 75w/90 where it's called for.
Which differential do you have, and what do you plan to do with your truck? Also, what climate do you live in?
Sorry, I'm sure I should know all that by now since you've been a regular poster, but I forget!

My thinking is that, with most of us, the 75w/90 gives you plenty of protection and a little easier flowing and all that. If you use the truck hard, carry lots of heavy loads, have a lot of power in your engine, live in a consistently hot climate, then the 85w/140 is the stuff.
The other reason I tend to go with the thinner oil is that on my lighter duty trucks at least, I can use the same stuff in the front diff, the rear diff, the transfer case, and the manual transmission. And I hate having multiple oils for one single vehicle!

So I'm not against your choice. Just wondering if it's justified for it's more gear cushioning and thicker flowing properties.

Paul

Jun 18, 2019 | 04:41 PM

440 sixpack

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if you're in a warm climate it's better than 85-90. in cold weather it will be fine but I question if it flows as well to the hub bearings on a floating axle.

in any event I would use it.

Jun 18, 2019 | 04:56 PM

caravaggio2000

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Well I don't go hard on my 390, but when it eventually gets rebuilt it might end up with a bit more power than stock. I think the key here is I live in Florida, which is 75 when it is cold and living in a sauna on the Sun when it is hot.

Jun 18, 2019 | 05:36 PM

440 sixpack

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you're good to go then. I have trucks with 85-140 in them and it get's 35 below here some years, 20 below is expected. never had a problem but I prefer 85-90 for our area.

Jun 19, 2019 | 01:16 AM

Ozzie H.

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From: S.E. Louisiana;so far USA

Quote:

Originally Posted by caravaggio2000

If you're in Florida, that climate is similar to mine. I've used your choice for many years with no problems. If you were in AK, Canada, or Siberia my answer would have been different. Gear lubricants, like engine lubricants, have evolved a bit in the last 40-50 years. If you "must" have SAE 90W, you can find it at Amazon, but I suspect that you are better off with what you have already.

Jun 19, 2019 | 07:45 PM

caravaggio2000

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Finished. I've got to say, this little hand vacuum pump I picked up last year has turned out to be one of the best tools I've purchased. Really helped me bleed the brakes completely last year and today it did an excellent job of sucking the old gear oil out of the rear.

At first I thought it didn't get it all because I only pumped 2 quarts out (though it was not at the hole when I took the plug out), but it took precisely 2 1/2 quarts to fill it back up.

Didn't see any metal, so I think I'm good. Thanks forum.