Which TC Oil should i use?
 

Hey Guys,
I got an 1989 GMC 1500 4x4 350. I was told to put 80-90 in the transfer Case, and i confirmed it in my haynes manual. But i heard the newer trucks all use transmission oil in there TC.

So my Question is, Which one is better????

Thanx,
Steve

use what is say to put it

thats not what i asked though. Yes i know i should use what they recommend. But which one is better?

Look into a high quality synthetic like Amsoil, Royal Purple, Red Line, etc.

Amsoil is excellent - but expensive - especially up here in Canada. I run it in my quad - diffs and gearbox.... The more load on the truck - the better quality oil you should use....

Hey,
Another way to look at it i guess is - Is it better for thick oil on the gears to lube them..OR! Thin oil that is more easy to be splashed around to lube the gears??????

Any thoughts????......

And Yes i know more expensive synthetics are better. But what im trying to figure out is, is it better for thicker oil or thinner?

The reason i am askin this is cause Gm made the change from gear oil to Tranny oil for a reason, and was just wondering if anyone has had any problems with using one or the other or???????????

Any input would be appreciated

GMC89
It's not an issue of which one is better, not all transfer cases are the same.
Would you put gear oil in your transmission? or Transmission oil in your engine?
Which one is better?
They are both good for the what they were designed to do.
The newer transfer cases call for AT fluid because they have electronic shifting capabilities some what like your AT.
Hoped this helped you get an idea why different fluids are needed
vp

Jvp
You have half answered my question which others have not.
I was not aware of the newer TC electronics, And frankly thats another reason why i refuse to buy a New/newer truck...TOO MUCH ELECTRONICS.
Again thanx.

As per your fluid application, Those are not realistic.

But if you may know i have put engine oil in my tranny, it got me where i needed to go and my tranny was on its way out anyways.

The reason behind my madness is up where i am, alot of guys with older trucks run the AT in there TC because the 80-90 oil is too thick at -20 -30 Celcius, A buddy of mine went threw a couple tranny's becuase of it. Once he went to AT fluid his problem was gone.

Another example, My dirtbike (KX250) should have 80 weight oil in the tranny/gearbox. It works ALOT ALOT better with 5w-30 in it. Does Kawi recommend it, NO. Does it work better YES.

Dissagree? i've been running it with 5-30 for 3 years, NO PROBLEMS.

I do understand the application for fluids, And i am not trying to be a know it all or smart a$$. And i do not want to bite the hand that is feeding my knowledge, by all means im not trying to.

What i've been trying to get at is what if your application calls for different fluid then what is recommended????

GMC 89
I understand, at the same time I would be careful.
My truck is an 05 2wd crew cab, with 3.73 gears I do a lot of pulling a 6500lb trailer.
I mix the different wt. of Amsoil gear oil 1qt. 75-140 and the bal. 75-90., Why? Looking for the lighter wt. to keep close tolerance areas lubed and the heavier wt. to add additional shock value under heavy load.
I am not an Amsoil dealer, but again I only use synthetic oils in by vehicles.
I am sold on the fact that they just work better and run cleaner.
Example my wife's Honda would not pass smog inspection with newer conventional oil.
I changed the oil to Castor Edge and the car passed with flying colors.
Go figure.
I understand your concerns in cold weather, all the more reason for synthetics, they do cost more but they work.
Go to the oil company's web. sites and check out friction numbers. Friction is not our friend.
Good Luck
vp

The right fluid to put in your tc is transmission fluid. That is what gm recommends. I own a 89 gmc sierra 4x4 and i work for gm.