After reviewing a number of threads on the duramax forums, I decided to change my transfer case fluid (Dex VI) at 43k miles.
There is a great deal of information out there on the fact that the ATF in the transfer case gets hot and burns off. There are guys draining their transfer case at 100k miles and getting out 1/2 qt when the capacity is 2 qts.
At 43k miles I pulled out 1.5 qts, so this early I had already suffered some burn-off. It's an easy job to do. When the transfer case goes dry, this case suffers "pump rub" and basically the pump shaft wears a hole through the aluminum transfer case wall.
There is a representative of a manufacturer of transmission parts that wrote a paper in a trade publication around this pump rub problem recommending overfilling the transfer case to 3 qts and instead using synthetic 5w-30. Overfilling with ATF is not recommended as it is said it will foam if overfilled - the 5w-30 will not. Tons of guys have done it (3qts of syn 5w-30) and are reporting no-burn off and very long transfer case life on this regime. Theres a number of guys with 100k miles on 3qts of 5w-30 in the case with no problems. The bigger sample size is the guys with between 30k and 50k on 5w-30 in the transfer case with no problems. I'll leave the dispute out of whether to do this or go with MFG spec out of this thread.
I might do it out of warranty, but don't want to give GM any excuses if I have an issue. I may move to the Redline D6 ATF for my next change and I'll likely change it at 30k miles intervals since its easy and it only takes 2 qts. Word to the wise - use the speedo sensor hole at the top of the transfer case for filling - you'll never get a funnel in that tiny fill hole, even if there was access. Leave the fill hole open to verify right level of fill.
Anyhow, whatever fluid you choose, I wanted to let the duramax owners out there know that it's important to stay ahead of this.
There is a great deal of information out there on the fact that the ATF in the transfer case gets hot and burns off. There are guys draining their transfer case at 100k miles and getting out 1/2 qt when the capacity is 2 qts.
At 43k miles I pulled out 1.5 qts, so this early I had already suffered some burn-off. It's an easy job to do. When the transfer case goes dry, this case suffers "pump rub" and basically the pump shaft wears a hole through the aluminum transfer case wall.
There is a representative of a manufacturer of transmission parts that wrote a paper in a trade publication around this pump rub problem recommending overfilling the transfer case to 3 qts and instead using synthetic 5w-30. Overfilling with ATF is not recommended as it is said it will foam if overfilled - the 5w-30 will not. Tons of guys have done it (3qts of syn 5w-30) and are reporting no-burn off and very long transfer case life on this regime. Theres a number of guys with 100k miles on 3qts of 5w-30 in the case with no problems. The bigger sample size is the guys with between 30k and 50k on 5w-30 in the transfer case with no problems. I'll leave the dispute out of whether to do this or go with MFG spec out of this thread.
I might do it out of warranty, but don't want to give GM any excuses if I have an issue. I may move to the Redline D6 ATF for my next change and I'll likely change it at 30k miles intervals since its easy and it only takes 2 qts. Word to the wise - use the speedo sensor hole at the top of the transfer case for filling - you'll never get a funnel in that tiny fill hole, even if there was access. Leave the fill hole open to verify right level of fill.
Anyhow, whatever fluid you choose, I wanted to let the duramax owners out there know that it's important to stay ahead of this.