Check that Duramax Transfer Case!

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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.
 
That's what I'm going to do, but more importantly, just to realize these things run dry quicker than most transfer cases is the key to keeping them alive in my opinon.
 
I had never heard of this prior to your post. Good info for sure. The Redline D6(any of their atf's) will resist burnoff much better than any dino atf. It will be interesting to see what your results are using the D6 knowing burnoff is an issue. Keep us posted!
 
Royal Purple Synchromax will not burn off and is excellent in transfer cases. I know some of you will think I am nuts but I use their Syntractor III fluid in all my Kubotas. That stuff is lasting 3 times longer than the synthetc blend Super UDT fluid. Anyway,I has some leftover and I put it in the differential part of my daughter's Corolla automatic 60,000 miles ago. Still clean and purple as it was when it went in. I don't use their oils personally but their gear fluids are tough as nails.
 
Originally Posted By: xxch4osxx
What year is this truck? Would it not use Auto-Trak II fluid?


Nope, it's not an automatic transfer case. It's a new body style 2500HD in my signature. My previous chev avalanche used the autotrack II. Different transfer case. It just has 2Hi, N, 4H, 4L. No 4wd Auto.
 
Ah, ok, I was just wondering, as my Silverado uses the Auto-Trak fluid. I just don't understand where the fluid would escape from when it gets real hot though. My transfer case never loses a drop and I change it every 2 years regardless of milage.
 
Originally Posted By: Jim 5
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.

thanks for the 411. i have a 03 duramax/allison trans 4X4 at work. is this the same transfer case? mike
 
Originally Posted By: caravanmike
Originally Posted By: Jim 5
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.

thanks for the 411. i have a 03 duramax/allison trans 4X4 at work. is this the same transfer case? mike


I think they're all the same. It's a pretty easy job to do.
 
Its foolish to run any gearbox to 100k without maintenance, or even checking the level.
Too many are bedazzled by the maintenance guide in owners' manuals which is useless and worth wiping your ars with!

It should be changed every 30k/2yr.
You can use a UOA to prove any longer intervals if you want.

A full synthetic is the 1st upgrade that should always be considered. MTF/MTL is another option if you want a little better protection.
 
I'd like someone to explain how t-case fluid "burns off?" That would take temps at or near it's flash point (375+). I have seen up to 300 degrees in various full-time t-cases at times but there's very little moving in a part-time case to create heat when it's in 4x2 mode.

Leaks... maybe.

The NP-261 t-cases in the '01-07 do have a tendency to wear a hole in the case at one of the oil pump locating tabs and leak but it's not due to "burn-off" it's a locating tab that breaks. The lack of lubrication occurs after some or all of the oil leaks out. You can read about it below.
NP261
 
I didn't know Dex VI was approved for the T-case. Last thing I read from GM was that Dex VI was NOT to be used in the T-case.

Dexron III is being phased out as a product name. It is being renamed Manual Transmission Fluid and carries p/n 88861800 U.S. (88861801 Canada).

"If fluid p/n 88861800 U.S. (88861801 Canada) is not yet available when servicing a manual transmission or transfer case, Dexron III can be used in its place.

DO NOT use Dexron VI in place of manual transmission fluid in any manual transmissions or transfer cases that specify Dexron III, as a failure may result."

Has this changed?
 
Sunnyinhollister, it hasn't changed. Some new gearboxes come shipped with DexronVI now. I'm hoping that they either upgraded some seals to prevent DexronVI leaks, or possibly improved pumped/splash lubrication for the better flowing DexronVI. Or, GM simply changed the spec for some transfer cases and are crossing their fingers ;-)

Jim, I think that the average and instantaneous temp could easily be 100+ degrees apart. So, if the average fluid them is 300f, there could be plenty of hot spots cooking off the fluid. But, I'd wager most is lost from burping when too hot or gradual leaks not noticed over 100k.
 
undummy, I strongly disagree about the temps. Look at the power flow diagram for a late model NP t-case (they are largely similar) and see how much of it is in operation in two-sheel drive. Next to nothing. I suppose I should hedge my bets and not make such a strong statement without looking at the Np261/263, but still...

Automatic transmissions run hot, 200 degrees, most of the time, hotter than t-cases... why doesn't their fluid "burn off?" Their localized temps are probably much higher than even the hardest worked t-case.

In some of the cases of the pinholes in the NP t-cases, the loss of fluid was so slow that people didn't really notice much of a leak, e.g. no massive puddles.

I just don't buy t-case oil "burning off." Prove it to me if you can, anyone.
 
I definitely saw "weeping" at the top of the transfer case near the rear by what felt like 2 rubber grommets pressed into the top of the case. I wouldn't be surprised that it doesn't burn off, the reports weren't in any way scientific.
 
From what I have seen and read in my owners manual, all transfer cases in the GMT900 07-present GM trucks spec Dex VI in manual and auto transfer cases.
 
Again, I'd wager most is slowly leaked out over time not being noticed.

And, I'm not worried about 4x2 temperature. The same engine HP is going through the transfer case as is the transmission. The same vehicle weight is loading the transfer case as it does the transmission. Automatics have 7-12 quarts. Transfer cases have <3. It doesn't take much time in 4x4 to warm a fluid with that small of a sump in a work vehicle. I think that automakers spend too much time with cost accountants and statisticians. They've got the perfect formula to make that transfer case last the warranty period. Too bad the negligent pay the big bill after it expires.
 
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