Oil vs Dexron III in transfer case

[lmholmes11]

I just changed my transfer case fluid and it looks like the previous owner put motor oil or something besides Dexron III, in the t case. Which is better, I already replaced with Dexron III, is it ok to go from one right to the other?

[More Power]

I've heard of people using synthetic motor oil in the Txfer case. It may not matter from a lube requirements position, but I think the manufacturers use ATF due to a potential for fluid migration between the transmission and txfer case should a seal problem develop. I had this happen in the late 1980's in a GM truck I owned at the time.

Jim

[pete m]

I had a 2002 HD that had the dreaded "transfer case leak", previous owner never new about it and never checked it. He traded it in to a dealer, who put regular oil in it to slow down the leak and quiet it down, after I drove it a year it started to make noise from the transfer case, I then found this site, saw what to look for, got under the truck, saw it had the leak, drained the case which was almost empty anyway, and saw it was filled with thick motor oil, when I filled with ATF, it sounded terrible, and also leaked out fast, I wound up replacing the transfer case because it sounded so bad and was afraid it would break down and leave me stranded, found one on the internet from a supplier that came with a year warranty for $900 shipped to my door. That may be why yours had the wrong oil in it too?

[DmaxMaverick]

You MUST use ATF. Reason being, there isn't a lot of 10 weight motor oil around. Running motor oil, or gear oil, will starve it of lubrication. The pump just won't pump enough heavy oil. In every case heavy oil was in TC's I'm familiar with, required a premature overhaul. The problem isn't lubrication ability, but the ability to get the lubrication where it needs to go.

[Kennedy]

I use the same ATF that I run in the transmission which is generally Transynd. If it's noisy with ATF it's shot.

Put a wear plate in BEFORE the pump plate eats a hole in the case.

[THEFERMANATOR]

I'm running AMSOIL 5W30 SYNCHROMESH oil in mine. It has basically the same viscosity to it as ATF when hot, and is actually slightly thinner cold when compared to a regular DEX III. The other reason that people run a motor oil type oil instead of ATF is it has been found that regular ATF will actually boil off somewhat in a transfer case of a vehicle that gets worked hard as many have found that they would be low onm oil in the t-case with no visible leaks.

[tpitt]

I run Castrol 5wt 30wt synthetic in mine. I have for quite some time. I've also done the pump rub fix.

[Observer]

One of the first things I did when I got my 2002 GMC 3500, was change the TC [Transfer Case] ATF fluid ... swapping it out for (3 qts.) AMSOIL 0W-20 Full Synthetic.

Most others are using 5W-30, but living up north wanted something a little thinner. My TC is loving it and I have absolutely no noise or vibration. If I were located down south (i.e. Nevada, Arizona, etc.) I'd probably go with 5W-30.