Transfer Case Fluid

[NY Diesel]

I have a 2003 2500HD with a Diesel and an Allison Transmission. The dealership told me it has a MP263 Transfer Case. I was also told to use Decron III in the transfer case, When I drained the old fluid, it was not red. It looked like motor oil.

Any suggestions?

[DmaxMaverick]

The original fill, and service fluid, should be ATF. The same stuff recommended for the Allison tranny. Motor oil, while it may have sufficient lubrication properties, is too heavy. If the TC seems to be operating normally, I suggest a fill with ATF, and a short change interval (maybe a few thousand miles). Don't look back. Odds are, no harm done.

On the other hand, if the lube was very thin (like ATF or thinner), you may have issues with the TC (contaminated fluid or an overheat issue). Was the fluid level normal? A series of events (however unlikely), could allow fluid to migrate from a leaking rear tranny seal into the front TC seal. I've seen it happen, but it's a million to one chance.

[NY Diesel]

Have a 263 Transfer Case. Was told to use Dexron III ATF Fluid. When I drained the old fluid out (original) it looked like oil. Is the Dexron III the corect fluid.

2003, 2500HD, Diesel, Allison Transmission

[jjcsnlynn]

I just picked up an 04, and changed all my fluids. I put in Dextron VI on the advice of this forum. When it came out, it was pretty dark, but not as bad as the transmission. Mine has 173K, and I don't know when the diffs and transaxle fluids were changed. The filter on the tranny was dated 12/2006 so the tranny fluid could be as much as 5 years old.

Man you should have seen the front diff fluid...more like paste than fluid.:eek:

[Kennedy]

I'm a Transynd user. There is non better IMHO. One thing I heard from a very reliable source is that there may be a compatibility issue with DexVI and the older input seals on the Allison. Dex VI is also said to solidify at a warmer temp than DexIII.

[rapidoxidationman]

Dex VI is also said to solidify at a warmer temp than DexIII.

???

Meaning that at colder temps the IV won't flow as well as the III?

But the Dex IV is a full synthetic (at least as it is labelled at the local NAPA). Does that not mean it has better flow properties, hot and cold, than III? Isn't that why GM says to replace III with IV in the transmission?

[Gapper_ca]

I have a 2005. when i changed to fluid it was black as well. then changed it on a short interval and it was very dark. later on i had to replace the entire transfer case. the bushing had come loose and was spinning around inside , full of metal fillings and such. if it is very dark i would check it out. cost me over $2000 to get it rebuilt, should have just bought a rebuilt one, but did not reliaze all that was poched on it.

[CoyleJR]

I am about to change my transfer case fluid for the 5th time in 180k miles. I have always used the GM owners manual recommended fluid GM p/n 12378508. The new/fresh fluid is a blue/green color and a dark dirty motor looking fluid after use. It appears that some DP members are draining the original blue/green fluid that looks like dirty motor after use and replacing it with ATF. Has GM made the determination that ATF is better than the owners manual recommended GM p/n 12378508? I have never had any problems with my transfer case and only want to use the best fluids in my truck. What is the VERY BEST fluid to use in my TC??????????
Thanks
John

[DmaxMaverick]

I am about to change my transfer case fluid for the 5th time in 180k miles. I have always used the GM owners manual recommended fluid GM p/n 12378508. The new/fresh fluid is a blue/green color and a dark dirty motor looking fluid after use. It appears that some DP members are draining the original blue/green fluid that looks like dirty motor after use and replacing it with ATF. Has GM made the determination that ATF is better than the owners manual recommended GM p/n 12378508? I have never had any problems with my transfer case and only want to use the best fluids in my truck. What is the VERY BEST fluid to use in my TC??????????
Thanks
John
The part number you posted is the WRONG fluid. That's Autotrac II fluid. It is ONLY for electronic/auto 4x4, which is NOT available on a 2500HD or 3500 GM truck. That fluid is designed and recommended for only 2500 (non HD) and lesser vehicles with auto 4x4. Your 4x4 system is electric, NOT electronic. Your transfer case should be serviced with ATF, the same fluid you should be using in the transmission. I recommend synthetic for both, especially if towing, and absolutely if towing heavy or frequently. The owner's manual covers several vehicle models, and they are not all the same.

[CoyleJR]

DuramaxMaverick,

I will replace the current fluid with Dexron VI full synthetic.

Thanks
John