Technical Gear Oil

I'm working on a 10 Bolt rear end, and went to buy the gear oil to put in it. Haven't bought any in a while, and was surprised by the prices these days. Factory recommends using synthetic (which I bought some)............$50 a gallon at Oriellys. Factory says a little less than 3 qts are needed, so I bought a gallon rather than 3 qt bottles.
Now all these rear ends have been around forever and seem to last forever......without synthetic oil and virtually no maintainance of any kind. I'm the kinda guy who will always spend extra money to get quality stuff, but I really have to question whether this is necessary. Its a simple open drive in a daily driver. If it was a posi of some kind I wouldn't mind so much. In the near future I expect to be assembling several rears that WILL have posi units in them. Whats the best oil for them ?

 

Haven't bought any in a long while, but the Royal Purple synthetic gear lube is good stuff. I used it in shaft-drive motorcycle final drives, it reduced running temps by a good 30%. Don't remember if it was rated for a clutch-type posi, you'll have to check on that.

 

I doubt you can go wrong with any name brand that has the additive for posi rears . Mark Williams has their own product , Torco .

 

I use walmart GL-5 80w-90, fifteen bucks a gallon. But then, I've been known to use what works, not what's "best".

 

You can always buy a bottle of stink oil and add it to regular gear oil.

 

as an experiment, i switched my gashog pickup over to synthetic in all the right places: engine, trans, both axles. no difference.

 

^^^they are all smilin' at cha now! (and for next 10K)

 

On the newer trucks, I think they recommend synthetic in the rear end because they know no one will ever change it, and the want to give it the best chance of survival. But us gearheads are better about maintenance than the normal driver, aren't we?

 

Synthetics do offer some advantages. May be good for an extra mph or so if you're racing on the salt or dry lake bed. For the average hot rodder probably not necessary. Good old GL-5 mineral oil should do the trick for most of us I would think. In your daily driver you might like it for the fill it and forget about it benefit. For commercial trucking, they might gain a slight fuel economy benefit, which cam add up to real dollars when spread over thousands of trucks, but probably not a great benefit for the classic car enthusiast. For limited slip or posi diff's it is the lubricity additives that are important, not synthetic properties.

 

A cobblers shoes are always worn. A roofers roof always leaks. A mechanics car is always broken. This one I love the best. An accountant is always broke.

 

It’s funny that you mentioned that. I just bought some filters for my OT SUV and I noticed that they had a more expensive “severe duty filter” by the same company. A little research and I found out it is actually less efficient than the standard filter. It is designed to go farther between changes with out clogging up. Geared toward the people that don’t service regularly. Less for more. Crazy? Clever marketing?

 

Recall early tests where either a slight improvement in milage, and more hp available since less internal friction. Likely over time as the contaminates lessen the lube qualities.

 

I bought my first race car from the guy who drove for me for 3 years. He had been using LE (Lubrication Engineers) gear oil, it's dyed red. He said it dropped the temperature of the rear end considerably. During an event you might change the rear gears 3 times. I watched guys not using LE lube pull out gears that were almost smoking. My QC gears were hot but you could handle them with a shop towel. I've used LE gear oil in everything I own ever since then.

 

Never had a gearbox fail with the old style gear lube....In fact the higher in sulphur the better...

 

I think you can use about anything. 80/90, 75/140. I would get the cheapest stuff around. Easy to over think it. It’s gear oil. I used leftover 75/140 I had from work in my 9 inch. It’s synthetic but I would not have bought it.


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yup, the worst modern gear oil is way better than the best old gear oil

 

My boss has a 05 dodge diesel pick up and changed all the fluids over to shafers synthetic oils, trans, transfer case and rear end and he gained 1.5 mpg doing it. And he keeps excellent track of his mpg.

His brother did it later and got about 1.5 in his hemi pick up.

So I'd say some of it has merit.

 

I know from experience working in the dealerships the big switch to synthetic any fluid is for a slight benefit in fuel mileage and also for extended service interval ( if any interval at all !). Most transmissions and diff are now SEALED FOR LIFE !! Ok sure

at Toyota the newer cars took a 0-w20motor oil and was about double the existing 5-w20 oil being used. Toyota issues a bulletin for customers stating “ for cost savings 5w-20 could be used with no ill effect but you may notice a decrease in fuel mileage.


I dunno for non racing, non heavy abuse applications regular old 80-90 will work just fine.

 

jaws dropped at the tavern when i told the guys that modern standard transmissions use ATF!

 

Have used Redline Shockproof w/ great results