LBZ: Synthetic lube for transfer case

[Chevy1925]

I have run mineral oil based Dex III in my 241 case for 50k miles, and the oil level NEVER dropped, so I dispute the "evaporation" claim. Note that this case is very similar internally to the 261/263 cases, and my use included long stretched of high speed highway driving, lots of in town (were talking AZ heat here), and a LOT of wheeling. And by wheeling, I don't mean puttering down dirt roads in 4WD, I mean actual wheeling:

.

I use the hell out of my 4wd as well and have had my ATF evap many times. hi speed 4wd (60+mph) on the freeway in snow/ice conditions as well as WOT runs through parking lots doin drifts and cyclones and off roadin in teh cinders for many many minutes at a time really over heat that trans fluid. at 3k, my t-case fluid (or what was left of it) was black and nasty. Put 5w30 in and it doesnt evap, if not maybe a 1/8 of a quart, and it still carrys a gold color after 3k. Rock crawlin wont get that t-case very hot either btw, puttering down roads in 4wd probably gets that case hotter than rock crawlin unless you run WOT on every rock.

 

[MaxPF]

So you post up a picture of a truck that does not use this transfer case and you in particular have not seen this problem with your transfer case and call b/s? Tell me how much study you have done on this.
How many T/C's have you looked at in the Duramax? What do you do for a living besides diagnosing these trucks on the internet? Have you actualy seen more than one tranfer case. from the outside?
I just love exSperts.

Ya know, rather than being a sarcastic tool, maybe you could explain to a poor dumb ol boy like me what makes the 26x case so special that it gets hot enough to evaporate ATF in such a short time? Especially since no other case seems to have this issue...

 

[MaxPF]

I use the hell out of my 4wd as well and have had my ATF evap many times. hi speed 4wd (60+mph) on the freeway in snow/ice conditions as well as WOT runs through parking lots doin drifts and cyclones and off roadin in teh cinders for many many minutes at a time really over heat that trans fluid. at 3k, my t-case fluid (or what was left of it) was black and nasty. Put 5w30 in and it doesnt evap, if not maybe a 1/8 of a quart, and it still carrys a gold color after 3k. Rock crawlin wont get that t-case very hot either btw, puttering down roads in 4wd probably gets that case hotter than rock crawlin unless you run WOT on every rock.

I have done all those very same things. FWIW, the 241 is a part time chain drive case with planetary reduction, VERY similar to the 261. The only difference (in my particular case) is that I don't have a pair of leaky slip yokes. My front output was fixed yoke from the factory, and I installed a JB Conversions slip yoke eliminator for the rear output (which eliminates the needle bearings supporting the drive sprocket on the main shaft). I have NEVER had my case get that hot. I have had the diffs too hot to hold my hand on, but never the t-case. Must be a 26x thing.

 

[McRat]

The difference with our trucks is that we run over 100mph in 4x4 with high amounts of HP being pumped through them. The thermal loading is really high compared to off-roading.

 

[MaxPF]

The difference with our trucks is that we run over 100mph in 4x4 with high amounts of HP being pumped through them. The thermal loading is really high compared to off-roading.

If only Mike could have given such a civil explanation

So, do Dodge and Ford have this problem with their 27x cases, or is this strictly a 26x thing? Seems strange that desert race vehicles (like those at the recently completed King of the Hammers) don't overheat gear drive cases on long fast sections, but these trucks overheat chain drive boxes during 1/4 mile sprints in high range...

In any event, if synthetic lube is the answer, then why not synthetic ATF over motor oil?

 

[McRat]

If only Mike could have given such a civil explanation

So, do Dodge and Ford have this problem with their 27x cases, or is this strictly a 26x thing? Seems strange that desert race vehicles (like those at the recently completed King of the Hammers) don't overheat gear drive cases on long fast sections, but these trucks overheat chain drive boxes during 1/4 mile sprints in high range...

In any event, if synthetic lube is the answer, then why not synthetic ATF over motor oil?

There aren't a lot of off-road race trucks that pump 1500+ ftlbs through their transfer case or weigh 6000+ lbs.

And yes, many off-road (and roadrace) race vehicles run external coolers on the:

Trans, Diff, T-case (if app), and Power steering.

Even my stock Z06 has a factory trans temp sensor that throws a light when you overheat the trans. And that's only 400ftlb through a T-56 (very stout trans).

I've even dusted a powersteering pump through overheating when roadracing. It had a cooler, just not big enough.

Casper will puke T-case fluid (not much, but some) when hot-lapped at the dragstrip with the factory fill.

If you aren't racing, I'd follow the GM recommendations. When racing, listening to experts who have seen hundreds of Dmaxes running over 500rwhp is probably good insurance.

 

[Bammer]

I asked a guy who worked at NP about the motor oil in the TC trick, he did not recommend it and then he was bashed unmercifully until he stopped posting . (this was on another site) Too bad

Comes down to checking the fluid instead of the out of sight out of mind mentality.

 

[Mike L.]

I asked a guy who worked at NP about the motor oil in the TC trick, he did not recommend it and then he was bashed unmercifully until he stopped posting . (this was on another site) Too bad

Comes down to checking the fluid instead of the out of sight out of mind mentality.

I remember that. He was not bashed because of the motor oil but because he denied there was a pump rub problem.
Motor oil would not be necessary if prople would check their TC fluid on a regular basis; but they don't and neither do their lube men or techs.
Using motor oil will give you a lot more time in between checks.
It is not uncommon for us to drain a TC and find only about half a quart of fluid in it with no signs of a leak. And no itdid not go into the trans as the trans fluid is right on.

 

[Bammer]

I remember that. He was not bashed because of the motor oil but because he denied there was a pump rub problem.
Motor oil would not be necessary if prople would check their TC fluid on a regular basis; but they don't and neither do their lube men or techs.
Using motor oil will give you a lot more time in between checks.
It is not uncommon for us to drain a TC and find only about half a quart of fluid in it with no signs of a leak. And no itdid not go into the trans as the trans fluid is right on.

RIGHT! Forgot the pump rub issue detail he denied exsisted !:banghead:

 

[oscyjack]

Might as well revive this one.

When I bought my truck, I took the advise given to me to fill my transfer case with 30w. However I was not made aware of the extra quart through the speed sensor. Is that because the oil behaves differently at temp than ATF and needs the extra quart to protect the case?

I asked Evan today what he suggests and he said ATF. He and Mike saying that is good enough for me. And I will switch it this evening. I check my fluids religiously so not worried about evap. I am wondering if running only 2 quarts of 30w in the TC over 25k miles is an issue. Still plenty full in there, just curious if I ran it low or not.

 

[N2BRK]

To each his own. I've been using 5/30synthetic for about 90k. When I had a booboo and needed a new cover, George said he'd never seen a t/c so clean inside. I figure that's worth a few points.

 

[oscyjack]

two or three quarts? Im more concerned with fluid level since i filled to weep and closed her up. Have verified level or added a couple pumps when needed. Hadn't seen the 3 quart business til today and figured I better add some in needed

 

[WolfLMM]

I've had 5w30 in the lb7 for 100k, no problems to speak of.

 

[WVRigrat05]

I ran syn 75-90 in my LLY for 150k.
I've had the cheap 80-90 in my LMM for +/- 20k now. I'm going to drain it soon and see what it looks like and put some Royal purple 75-90 in it since I've got 15 gallon in the garage doing nothing.

 

[oscyjack]

gear oil in the xfer case? subadub lol. I probably won't be doing that over here, 30w was straying far enough from the spec for me lol

 

[WVRigrat05]

**** it. I started out with Mobil 1 5-30.

The LLY had 50k and the trans fluid was about gone and the yoke seal was leaking so I said **** it and put gear oil in it. Never touched it again until 130-140k and it was a dark golden still but was glittery from I'm guessing the pump rub.
Changed it again at 200k and it was a dark golden with no metal. Still had the same shit at 230k when the truck went away.

So I figured I'd see how the newer transfer liked it, it might take it, it might break.

 

[WVRigrat05]

Mike L, have you ever ran gear oil in the new transfers or seen any die from it

 

[oscyjack]

Let me know how she does!

I need someone like you around to make me look like less of a bull on some of this stuff haha. i like the idea of it with beefy fluid, but im not a fluid engineer so ill leave that to better heads. still subbed lol

 

[Mike L.]

Mike L, have you ever ran gear oil in the new transfers or seen any die from it

Gear oil tends to make the gear selection too sluggish and may be too thick to get lube into tight places. Most companies did away with gear lube when they went to aluminum TC's. Gear oil doesn't lubricate the seals either.

 

[THEFERMANATOR]

Not to mention the transfer case pump is not meant to be pumping gear lube. I've seen 231's in jeeps bite the dust from runni,g gear oil because the pump couldn't get enough oil up to the front of the case, and the planetary's starved for oil.