Transfer case fluid

[Enforced_Leo44]

I'll soon change my TC fluid, I was scrolling through the lubrication order manual (LO 9-2320-280-12) and saw that it says to use Dexron 2 ATF, 3.5qts
But I've also seen people on this forum as well as on youtube say that it's recommended by GM to use manual transmission fluid

Is there a reason to use one or the other?
Also, would Dexron 3 be compatible with Dexron 2 if I chose to go the ATF route?

 

[Coug]

DEX 3 replaced DEX 2 for all applications. DEX 3 is what you want to use.

So what happened with GM is they came out with DEX 6, and started having an increase in transfer case issues/failures.
So what they did was make a new label for DEX 3 and called it "manual gearcase fluid" and a new part number for it.

04-07-30-037E GMC Technical Service Bulletin

04-07-30-037E GMC Technical Service Bulletin

www.tsbsearch.com

From the GM bulletin

The content of this bulletin does not apply to manual transmissions or transfer cases. Any vehicle that previously required DEXRON®-III for a manual transmission or transfer case should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case Fluid. Some manual transmissions and transfer cases require a different fluid. Appropriate references should be checked when servicing any of these components.

 

[Enforced_Leo44]

DEX 3 replaced DEX 2 for all applications. DEX 3 is what you want to use.

So what happened with GM is they came out with DEX 6, and started having an increase in transfer case issues/failures.
So what they did was make a new label for DEX 3 and called it "manual gearcase fluid" and a new part number for it.

04-07-30-037E GMC Technical Service Bulletin

04-07-30-037E GMC Technical Service Bulletin

www.tsbsearch.com

From the GM bulletin

The content of this bulletin does not apply to manual transmissions or transfer cases. Any vehicle that previously required DEXRON®-III for a manual transmission or transfer case should now use P/N 88861800. This fluid is labeled Manual Transmission and Transfer Case Fluid. Some manual transmissions and transfer cases require a different fluid. Appropriate references should be checked when servicing any of these components.

Aaaaah I see, makes sense, thanks for the detailed answer, time to go get some Dex 3 then!

 

[Bulldogger]

Check if your transfer case is part of the cooling loop for the transmission. Mine is. I thought ALL were. This means your transfer case fluid is the same as the automatic transmission and is being constantly shared/changed.
BDGR

 

[Mogman]

Check if your transfer case is part of the cooling loop for the transmission. Mine is. I thought ALL were. This means your transfer case fluid is the same as the automatic transmission and is being constantly shared/changed.
BDGR

This is incorrect, the cooling fluid from the transmission goes through a closed loop (cooler) in the transfer case, the two fluids never mix unless the cooling loop in the transfer case is bad.

 

[Enforced_Leo44]

This is incorrect, the cooling fluid from the transmission goes through a closed loop (cooler) in the transfer case, the two fluids never mix unless the cooling loop in the transfer case is bad.

oh yeah I think I read this somewhere, if that cooling loop goes bad, you got transmission fluid overflowing the transfer case, stressing the seals and pushing ATF in the vent lines

 

[frauhansen]

Check if your transfer case is part of the cooling loop for the transmission. Mine is. I thought ALL were. This means your transfer case fluid is the same as the automatic transmission and is being constantly shared/changed.
BDGR

In that case, it doesn't matter how after a few minutes the same, no matter what you put on which side.

 

[Bulldogger]

oh yeah I think I read this somewhere, if that cooling loop goes bad, you got transmission fluid overflowing the transfer case, stressing the seals and pushing ATF in the vent lines

This happened to me last Summer, I am in process of replacing all cooling loop hardware and getting a new transmission... Still looking for one. Hard to find time. I can say with certainty, my transmission/transfer case interface is NOT a closed loop, because all the ATF in my transmission vented out the transfer case and caused the clutches in the transmission to burn up.
BDGR

 

[Mogman]

This happened to me last Summer, I am in process of replacing all cooling loop hardware and getting a new transmission... Still looking for one. Hard to find time. I can say with certainty, my transmission/transfer case interface is NOT a closed loop, because all the ATF in my transmission vented out the transfer case and caused the clutches in the transmission to burn up.
BDGR

You can run without the cooler connected, the same basic transfer case in civy use does not have a cooler, unless you are pulling hard for hours on end in low range.

 

[Bulldogger]

You can run without the cooler connected, the same basic transfer case in civy use does not have a cooler, unless you are pulling hard for hours on end in low range.

Agreed. It's setup that way now, both Trans and TC in bypass, to get me home*. I've not driven much since (on purpose). I still have to choose whether to add the transfer case to the cooling loop when I replace the transmission. I did buy an oil and ATF cooler already, having decided it was best to keep transmission cooling.
BDGR

* with the damage done to the 3rd and 4th gear clutches I can't make better than 45MPH, or I might just keep driving it in bypass...