Check that Duramax Transfer Case!

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Originally Posted By: Sunnyinhollister
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?


Guess I better change it out to M1 ATF. Don't know what to believe here. Especially with the newer manuals specifying Dex VI. Lucky for me it's an easy job.
 
I'd wager that heat is a factor. I've checked more than enough cases filled with ATF that was black as midnight not to think that...
 
Mine came out dark cherry red at 43k miles. At least I know it's ATF in there and not Autotrak II. I will admit the owner's manual is really vague as to what goes in there.
 
According to my sources, the NP-261 holds 5.1 quarts.

In four wheel drive, undummy, you are right. They can get pretty hot, though chain drives and planetaries don't generate much heat. I had a temp gauges in both an NP208 chain drive case and an older gear drive NP-205. Both had the mucus 'wheeled out of them in Western Colorado and Utah in 100+ degree summers. The gear drive t-case could get to 250F very easily rockcrawling. The NP-208 never broke 200F even once, even holding just 5 quarts (plus a skosh). I did use syn fluid and even a synchromesh fluid in it, so that would account for some lowering of temperatures. I did not have a temp gauge on it when the truck ('83 Blazer diesel) was stock. 200F is hot but not near hot enough IMO to boil or burn off oil.

On the other hand, in my past years as a factory trained Land Rover tech, when the first BW viscous-coupled, fulltime, chaindrive t-cases were introduced in the Range Rover in 1990, those puppies got blisteringly hot on the highway, but ran cooler in low range with the center diff locked. On the street, we would see the oil stinkin' and burnt dark brown or even black in 30K (but no loss of fluid). That bespoke 300+ to me but, again, no drop in level.

Anyway, oil oil capacity, 'wheeling and high temps necessitate more frequent service, certainly, but no "burn off," agree?
 
I'll agree. Volatility is there but might account for a couple percents of the fluid on a 'FULL' transfer case. These leaky xfer cases are losing 1/4 to 3/4 of their capacity over an interval. Can't cook that much off.

Now, what happens to the ATF temp when the sump level drops?
Transfer case temp at 2 quarts vs 1 quarts vs the final pint left just after the warranty expires?
 
Originally Posted By: unDummy
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 am taking your advice on this and am going to switch over to M1 ATF. I'm just wondering what it is about Dex VI that would cause a failure (as compared to Dex III) and how rapidly that failure is likely to occur. I thought I would wait until the weekend (a few days) to change it.

Also, I'm just interested in knowing the theory around why this failure would occur with Dex VI.
 
Not speaking for undummy, but if the factory manuals call for Dex IV, what "failure" are you anticipating? If yours calls for Dex III, use it. The oil pump tab/case failure is a design issue separate from any lubricant. The best lubricant on the planet will not prevent it from happening. I'm sure M1 ATF is a fine replacement for either Dex III or Dex IV but it isn't smart enough to fix a major design flaw.

Or are you still convinced the the ATF mysteriously "boils way." If so, drive your trucs a fair distance in 2wd on a warm day. Go under and put your hand on it. It will be warm but not blistering hot. To boil away ATF, it would have to be smokin' hot and would burn your hand.
 
Its not occurring with just DexronVI. I've seen too many dry gearboxes and can say all were caused by negligent owners. So, if yours requires DexronVI, don't be afraid to use it. But, you don't have to.
You can play the DexronVI game by using Maxlife, Amalie, Redline D6 or Amsoil ATL :) These are all the 'thin' full synth's so you don't lose that critical MPG with your 7000lb 500hp SUV or truck :eek:)

I'd just use any full synthetic ATF from the closest local auto part or dept store. BTW, I regularly use Chrysler's ATF+4 in place of Dex/Merc in transfer cases and front or rear-ends that require ATF. Its the poor man's synth substitute.
 
Originally Posted By: unDummy
Its not occurring with just DexronVI. I've seen too many dry gearboxes and can say all were caused by negligent owners. So, if yours requires DexronVI, don't be afraid to use it. But, you don't have to.
You can play the DexronVI game by using Maxlife, Amalie, Redline D6 or Amsoil ATL :) These are all the 'thin' full synth's so you don't lose that critical MPG with your 7000lb 500hp SUV or truck :eek:)

I'd just use any full synthetic ATF from the closest local auto part or dept store. BTW, I regularly use Chrysler's ATF+4 in place of Dex/Merc in transfer cases and front or rear-ends that require ATF. Its the poor man's synth substitute.


I don't know what mine requires due to the vagueness of the owner's manual language referring to both "Automatic" transfer cases and "Manual" transfer cases. My truck is a new body style in a crossoever year when old and new style were both offered. I believe I have a "manual" transfer case that is engaged electronically. It has 2H, 4H, N and 4L on the electronic dial. I believe they are referring to trucks with the following options when they refer to an automatic transfer case "2H, 4WD Auto, 4H, 4L".

If it's an automatic, it takes Autotrack II like the 1/2 Tons. If it's manual it takes If fluid p/n 88861800 U.S. (88861801 Canada) which appears to be Dex III. If it's a 2008+ NBS, then it takes Dex VI like all of the guys on the Duramax forums are saying.

I think it's an electronically operated manual transfer case, in the sense that it has no function to automatically engage 4WD from being in 2WD to send power to the front diff when it detects rear slip (when 4WD Auto is selected - which I don't have). I had that transfer case on my previous Chev Avalanche. That's why I think it takes Dex VI or possibly more properly Dex III. But if not, and there are probable or possible failures on Dex VI then I'll switch to Dex III M1 ATF which will be a better fluid than the OEM serial numbered Dex III, and probably at 1/2 the price.

Any thoughts here?
 
Yours sounds like a manual gearbox to me. The "dial" controls the servos instead of you moving a mechanical lever. So, use DexronIII(MT/transfer case oil) for older and DexronVI for newer. Anyone can use a full synthetic DexronIII regardless.

"4wd auto" sounds like AutocrapII as it has to, while moving under load, smoothly engage 4wd via clutches vs the mechanical clunk that you'd get from the e-servo locking the mechanical transfer case instantly. AutotrakII is the friction modified fluid that make the "auto 4wd" consumer friendly.
 
Yes it would, as would any full synthetic ATF available that mentions the Dexron spec.

I don't believe that the maintenance intervals are proactive enough, & is why I won't recommend the new GM fluid or the TES-389 mineral ATFs, or the Dex/Merc generics that are available.
 
I am very familiar with this topic. So much so, that when I was a mod over at a Dmax site, I wrote a whole article as a "sticky". You can go over to dieselplace.com and read it in the M&F forum.

Bottom line is that there is a HUGE amount of misinformation regarding the background of the failures and the source of the "fixes".

"Pump rub" is a mechanical issue that affects the K 2500/3500 HD trucks with 261/263 xfer cases. It has NOTHING to do with the lube you use, or lube level. If you get "pump rub" you will still suffer catastrophic failuer if you even used the world's most expensive, perfect oil. Pump rub is a mechanical failure, period. A small spring clip can eventually fail and allow the alumimum pump body to run a hole into the magnesium xfer case (alum is soft, but mag is softer, believe it or not!). Many of us that know of this problem purchase and install a true mechanical fix so that it never happens; it is the Achillis Heel of this xfer case.

As for the man suggested the use of 3 qts 5w-30 in a xfer case that calls for 2 qts ATF, well, I both personally spoke with him on the phone and exchanged emails. This guy owns a reman shop; he not an engineer, he has no experience with tribology, he never spoke with the engineers at NV (I did!). He simply SWAG'd a lube and it works fine; but that is NOT the same thing as selecting a lube based upon design and performance criteria. His "experience" came from some rebuilds his shop did, and they noticed low (or no) lube levels in the failed xfer cases. I agree that low lube (or no lube) is a very bad thing for anything like a transfer case. But that is NOT the fault of the lube; rather, that is a failure of the owner/operator to maintain the proper lube level! Would you run 80w-90 gear oil in your Dmax engine just because it was "thicker" and "better"? That was his answer to me when I asked him why he suggested motor oil in place of ATF. He had ZERO explination as to why "thicker is better", nor could he address cold flow properties, etc. He may be a famous part-time racer, and run a lot of business through his shops, but I was not impressed. He specifically admitted to me that he never called GM, NV, or any other source before making his choice. I personally spoke to him, the product engineer at the NV plant, and sourced several other industry leaders; NONE of them agreed with the use of motor oil in an ATF application.

I will never understand why some people are so anal about their engine oil, but literally treat the diffs and xfer cases as though they are fill-and-forget devices. Neglect is no reason to displace blame, folks.

Now, be aware that I am NOT saying the use of 5w-30 will destroy a xfer case; clearly many people use it and it works fine.

What I am saying is that one man took a few exmaples of failures, blamed the lube for the owner's lack of maintenance, and then used absolutely no research before suggesting an alternative fluid.

Again, if you want the whole story, read my sticky over at dieselplace.com. However, consider yourself hereby forewarned; that site has a high percentage of zealots and they lay siege to common sense and factual basis, and bow to the lords of mythology, hype and rhetoric. (One of the many reasons I quit moderating over there ...)

Bottom line for this topic is this:
1) check ALL your fluids; failure to do so is your fault - not the fluid's
2) if you want to "upgrade" your fluid in the GM HD trucks, you can choose a nice DEX III type ATF in synthetic form
 
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Actually, unless I see back to back tests comparing ATF to motor oil, MTF/MTL or 90wt gear oil, I won't jump to the conclusion that it has nothing to do with the fluid. Spent too much time in drivetrain component testing.

Running low and ignoring sensible maintenance certainly will add to the expectation of failure.

The pump rub, or pump hammering the case, is an engineering defect. Nothing will prevent inevitable. But, I'd wager that with the thicker the fluid, the longer it would take. Rattling a spoon in your cup of coffee is easier than rattling that same spoon in the cup filled with honey. Eventually, either your cup or spoon wears out. Viscosity is your friend.

The real question is, can I get an additional 25k, 50k, 100k, or 150k out of the case with different fluids from the get go? And, the 50% thicker motor oil might be the ticket to another 25k-50k before you hammered the hole in the case, when compared with DexronIII. I would use MTF/MTL instead of motor oil. Fluid is your pump rub's shock absorber.

And, the warmer a metal gets, the softer it is. A case running at 150F will be harder than a case running at 300F. So, any drop in temp is a plus besides the normal 'visc curve' benefits of thicker cooler fluid, and the proper level or overfilled level. Everything mechanical wears out. Its up to us to decide if we can extend the life, or prevent the wear with simple upgrades.

The effects of a mechanical issue can be reduced more than one way, prior to the inevitable required repair.

So, if you are 100% sure that you're mechanicals are prone to failure, than don't bother with the factory recommendations at all. Fill that case with Redline MTL/MT90 or Amsoil MTF/MTG. Top it off cold at every oil change. Keep it overfilled by a pint or quart(use the tilt vehicle top off).

And, keep driving 'cause you know that one day you'll eventually have to rebuild and upgrade it. PM, thicker quality fluid, good level, is all you can do now without rebuilding it.
 
Originally Posted By: dnewton3
I am very familiar with this topic. So much so, that when I was a mod over at a Dmax site, I wrote a whole article as a "sticky". You can go over to dieselplace.com and read it in the M&F forum.

Bottom line is that there is a HUGE amount of misinformation regarding the background of the failures and the source of the "fixes".

"Pump rub" is a mechanical issue that affects the K 2500/3500 HD trucks with 261/263 xfer cases. It has NOTHING to do with the lube you use, or lube level. If you get "pump rub" you will still suffer catastrophic failuer if you even used the world's most expensive, perfect oil. Pump rub is a mechanical failure, period. A small spring clip can eventually fail and allow the alumimum pump body to run a hole into the magnesium xfer case (alum is soft, but mag is softer, believe it or not!). Many of us that know of this problem purchase and install a true mechanical fix so that it never happens; it is the Achillis Heel of this xfer case.

As for the man suggested the use of 3 qts 5w-30 in a xfer case that calls for 2 qts ATF, well, I both personally spoke with him on the phone and exchanged emails. This guy owns a reman shop; he not an engineer, he has no experience with tribology, he never spoke with the engineers at NV (I did!). He simply SWAG'd a lube and it works fine; but that is NOT the same thing as selecting a lube based upon design and performance criteria. His "experience" came from some rebuilds his shop did, and they noticed low (or no) lube levels in the failed xfer cases. I agree that low lube (or no lube) is a very bad thing for anything like a transfer case. But that is NOT the fault of the lube; rather, that is a failure of the owner/operator to maintain the proper lube level! Would you run 80w-90 gear oil in your Dmax engine just because it was "thicker" and "better"? That was his answer to me when I asked him why he suggested motor oil in place of ATF. He had ZERO explination as to why "thicker is better", nor could he address cold flow properties, etc. He may be a famous part-time racer, and run a lot of business through his shops, but I was not impressed. He specifically admitted to me that he never called GM, NV, or any other source before making his choice. I personally spoke to him, the product engineer at the NV plant, and sourced several other industry leaders; NONE of them agreed with the use of motor oil in an ATF application.

I will never understand why some people are so anal about their engine oil, but literally treat the diffs and xfer cases as though they are fill-and-forget devices. Neglect is no reason to displace blame, folks.

Now, be aware that I am NOT saying the use of 5w-30 will destroy a xfer case; clearly many people use it and it works fine.

What I am saying is that one man took a few exmaples of failures, blamed the lube for the owner's lack of maintenance, and then used absolutely no research before suggesting an alternative fluid.

Again, if you want the whole story, read my sticky over at dieselplace.com. However, consider yourself hereby forewarned; that site has a high percentage of zealots and they lay siege to common sense and factual basis, and bow to the lords of mythology, hype and rhetoric. (One of the many reasons I quit moderating over there ...)

Bottom line for this topic is this:
1) check ALL your fluids; failure to do so is your fault - not the fluid's
2) if you want to "upgrade" your fluid in the GM HD trucks, you can choose a nice DEX III type ATF in synthetic form


Thanks.

I enjoyed your article on the diesel place and appreciate the time and effort you have spent on this point.
 
Originally Posted By: The Critic
I'll ask WhiteWolf and see if he has more info on this issue.


Sounds good.

Thanks to everyone, and particularly unDummy and dnewton3 for a very informed discussion on this point.
 
Most often, I'd agree with undummy on his point about the "rattling spoon" theory of abrasion, but that does not really apply in this situation.

This is simply a true pressure/force rub scenario of the aluminum pump body against the magnesium case wall. The pump body force reacts to the direction of the vehicle driving in a particular direction. Since driving forward is about 99.99999% of what we do, the force is constant against the case wall in one direction. The pump body does not bounce or rattle; this is a wear issue and not a pounding issue. When "pump rub" occurs, it is always in one specific spot, and has occured regardless of what fluid is used. Some Dmax owners have had pump rub occur even when using the 5w-30 motor oil alternative. NO FLUID CHOICE WILL AVERT PUMP RUB. While possible to choose a fluid so incredibly viscous that it could buffer the force effect, it would subsequently also be WAY too thick to lube the other things in the t-case it is supposed to protect. This is a link-plate chain driven case, and you need good lube flow into the plates to lube the pins, as well as having to be picked up via a pick-up tube and pumped by a small georetor. If you used a super thick fluid, you would be trading one form of destruction for another at that point.

You can visit a website called Merchant Automotive and they have a detailed sub-section for their high-quality pump plate replacement. In that section, they also have a link for a very detailed tear-down and replacement of the parts. If you review that, you'll understand the failure mode. I was very impressed with their detailed description and pictures; so much so that I used their directions to do my own installation of the "pump rub fix". I choose a "pump-rub fix" product from Riverside Gear, rather than Merchant Automotive, based upon price.

It is generally accepted that there are two kinds of GM drivers of these trucks with these specific t-cases; guys that have suffered from pump-rub, and guys that will eventually suffer from pump-rub. At some point, that little clip breaks (or dislodges), and then pump rub starts its evil work, slowly and methodically. You will NEVER know you have pump rub, until the hole is worn through the case wall, and by that time, it's too late! It has happened to guys with 35k miles on their trucks, and guys with 200k miles on their trucks, and everywhere in between. It will happen, it's just a question of when, and no fluid choice will stop it from happening. It's possible that a thicker fluid could slow the progress of pump-rub, but again, at a detrimental cost to other components in the t-case.

So, most of us that are aware of pump-rub do a pre-emptive fix. I took my case out at 10k miles and installed a high quality barrier plate that solves the problem. There are a few differing styles of fixes, but they all work well and no one I know of has had a failure once the fix is installed.

I would also like to note that "pump rub" is not necessarily the failure mode that Weinberg saw in most all the cases he was repairing. The failures he was seeing (per his own description on the phone to me, and in his article) were based upon little or no lube being present, but not because a hole was rubbed into the wall of the t-case. His main complaint was the simple evaporation of the lube; he suggested a thicker lube simply to slow the rate of evaportion, and also to over-fill the case by 50%. He was essentially blaming the fluid for leaving the case due to heat. Again, I believe it to be fundementally flawed to blame the lube for a simple lack of maintenance on the part of the owner. Use the proper fluid, do your checks, and you'll not have the problems he saw.

So, essentially we are coving two seperate topics in one discussion.
1) pump rub - which will eventually happen to all, time dependent
2) evaporation of fluid
Mechanical intervention is the only way to fix the issue of #1.
Proper maintenance is the only way to avert #2. (You can slow the evaporation by using synthetic or alternative fluids, but this does NOT remove the responsibility of maintaining fluid levels!



Hope that helps.
 
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Here we go with this "evaporation of fluid" thing again.

Dave, I'm going to need a lot of convincing and explanation on that before I believe it. ATF doesn't "evaporate" in an automatic trans. It doesn't "evaporate" in a manual trans. It doesn't when it's spec'ed in a power steering system. It doesn't in any other transfer case, seemingly EXCEPT the NP261/263. How is that possible?
 
dnewton3,

How many hours did it take to remove the TCase, take it apart, insert the pump barrier plate, reassemble and re-install?

Did you install one like they sell on the Kennedy Diesel site?
 
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