Can Synthetic ATF be a substitute for GM Automatic Transfer Case Fluid?

**TurboDiverArt** · 03-29-2006, 20:06

Just curious here. I need some and I’m not 100% sure I can get to a local Chevy/GMC dealer tomorrow to get some. In looking at the Royal Purple site, their Synchromax can be used as a substitute for GM 12378396 (Automatic Transfer Case Fluid). Synchromax is also used as a substitute for Dextron and Type F automatic transmission fluid.

Wondering if I can’t get to a GM dealer tomorrow, can I use synthetic automatic transmission fluid?

In checking the Internet, seems a number of places say you can also use regular Dextron III ATF. I’d probably put in Synthetic Dextron III replacement oil vs. regular ATF as GM says the correct fluid has extra anti-friction properties, which I would assume synthetic would be better for.

Thanks,
Art.

**AndyL** · 03-30-2006, 03:36

IMHO most cases it would be fine, expecially if you used a high quality fluid like Royal Purple. The one exception could be your Burb, GM went through several revisions of fluids attempting to cure the NP246 wear issues. The NP246 in the wife's Burb chucked the chain gears through the side of the case while driving home from Tampa Florida! And that was at 90K miles.

**DA BIG ONE** · 03-30-2006, 03:45

I have changed out my NP 246 AutoTrac w/completely new unit it is filled w/synthetic ATF and that is what is recomended by the manufacture.

GM calls for some blue stuff that helps the clutch pack but the syn/ATF does work.

**moedog** · 04-10-2006, 17:04

Been running mobil 1 synthetic atf in my transfer case for 50,000. no problems

**TurboDiverArt** · 04-10-2006, 18:18

I was able to find a GMC dealer that had the GM stuff in stock. Naturally I put it in, added a little less than 3/4 of a quart and in about a day it blew out and it's down by the same amount. Now I just need to figure out where the leak is. I'm assuming it's one of the drive shaft lip seals, at least I'm hoping that's what it is. Need to spray down and clean the case real good, fill it back up again and take it for a short drive to see if I can tell where it's coming out of.

Damn truck!

Art.

**DA BIG ONE** · 04-11-2006, 07:26

Originally Posted by TurboDiverArt

I was able to find a GMC dealer that had the GM stuff in stock. Naturally I put it in, added a little less than 3/4 of a quart and in about a day it blew out and it's down by the same amount. Now I just need to figure out where the leak is. I'm assuming it's one of the drive shaft lip seals, at least I'm hoping that's what it is. Need to spray down and clean the case real good, fill it back up again and take it for a short drive to see if I can tell where it's coming out of.

Damn truck!

Art.

Make sure your vent is not clogged first. The seals at the driveshafts do wear, the back one is just an easy change out, however the front output seal requires a special tool so you don't damage it, frt seal is around $50. US.

The following links will help ya for tool, seals, rebuild kits, rebuilt t-case, and even a new NP 246 t-case for under $1,000.

http://www.transfercases.com/

http://www.drivetrain.com/transferca...%20Model%20246

http://www.omegamachine.com/html/New...installer.html

**TurboDiverArt** · 04-11-2006, 07:53

Originally Posted by DA BIG ONE

Make sure your vent is not clogged first. The seals at the driveshafts do wear, the back one is just an easy change out, however the front output seal requires a special tool so you don't damage it, frt seal is around $50. US.

The following links will help ya for tool, seals, rebuild kits, rebuilt t-case, and even a new NP 246 t-case for under $1,000.

http://www.transfercases.com/

http://www.drivetrain.com/transferca...%20Model%20246

http://www.omegamachine.com/html/New...installer.html

Thanks for the info. I never looked at the T-Case seals, I assumed they both were standard transmission seal like at the tail of a 2WD transmission.

I assume the vent is on top? Never looked that closely at it. I'll have to feel around for it and check it out. Is it just a tube or one with a stopper top on it?

Thanks,
Art.

**DA BIG ONE** · 04-11-2006, 13:20

Originally Posted by TurboDiverArt

Thanks for the info. I never looked at the T-Case seals, I assumed they both were standard transmission seal like at the tail of a 2WD transmission.

I assume the vent is on top? Never looked that closely at it. I'll have to feel around for it and check it out. Is it just a tube or one with a stopper top on it?

Thanks,
Art.

The seals are simular but the front one is a PITA to seat properly.
The vent at top of t-case should have a hose going up firewall to a vent cap like tranny does, however, I've seen some w/just a little vent cap sticking out of t-case if you have this type install a hose setup.

**TurboDiverArt** · 04-12-2006, 06:26

Originally Posted by DA BIG ONE

The seals are simular but the front one is a PITA to seat properly.
The vent at top of t-case should have a hose going up firewall to a vent cap like tranny does, however, I've seen some w/just a little vent cap sticking out of t-case if you have this type install a hose setup.

Thanks again for the info. I'll try to take a look this weekend at it.

Art.

**TurboDiverArt** · 05-01-2006, 13:34

OK, I finally got a chance to look under the truck. I think I found the problem. Unless there is suppose to be a vent hole on the bottom side of the rear seal, I have a leak there.

I was looking and there is no fluid on the sides of the transfer case or anywhere forward of where the fill plug is. It

**MJEasly** · 05-01-2006, 18:03

Originally Posted by AndyL

IMHO most cases it would be fine, expecially if you used a high quality fluid like Royal Purple. The one exception could be your Burb, GM went through several revisions of fluids attempting to cure the NP246 wear issues. The NP246 in the wife's Burb chucked the chain gears through the side of the case while driving home from Tampa Florida! And that was at 90K miles.

Did she notice anything before the chain let go? My case is making a strange noise that changes with road speed. Sounds a lot like a chain rubbing inside the case or a badly lubed chain.

I would also like to know if there are any upgrade kits for this tcase. Seems like a lot of fluid drips out the back of the seal. IIRC, there is a manufacturer that makes a slip-yoke eliminator for certain cases, but not for this one.

**TurboDiverArt** · 05-01-2006, 18:24

Originally Posted by MJEasly

Did she notice anything before the chain let go? My case is making a strange noise that changes with road speed. Sounds a lot like a chain rubbing inside the case or a badly lubed chain.

I would also like to know if there are any upgrade kits for this tcase. Seems like a lot of fluid drips out the back of the seal. IIRC, there is a manufacturer that makes a slip-yoke eliminator for certain cases, but not for this one.

For what it's worth. Mine makes a sound that changes with road speed. I usually describe it as like rubbing sand paper together when on the highway. At lower speeds could almost sound like a chain sound. Add some fluid. with mine it's not too low and makes that noise. Only 1/2-3/4 of a quart and it's making noise.

Figure out where the leak is and fix it.

Art.

**autocrosser** · 05-02-2006, 10:34

My son's was actually leaking thru the yoke where it attached to the drive shaft. Not in the quantities described above but none the less enough to mee up a driveway. He found that one by putting a piece of paper down and tracking watching where it dripped after changing the seal several times. Sealing the joint cured it.

**DA BIG ONE** · 05-02-2006, 11:19

Originally Posted by MJEasly

Did she notice anything before the chain let go? My case is making a strange noise that changes with road speed. Sounds a lot like a chain rubbing inside the case or a badly lubed chain.

I would also like to know if there are any upgrade kits for this tcase. Seems like a lot of fluid drips out the back of the seal. IIRC, there is a manufacturer that makes a slip-yoke eliminator for certain cases, but not for this one.

There was a mod to the case to prevent wear through. The demon is the design, if you go off road get mud on the yoke and it dries the movement of the driveshaft in/out of case tailhousing acts like sandpaper. %$E* GM!

**DA BIG ONE** · 05-02-2006, 11:31

[QUOTE=TurboDiverArt]OK, I finally got a chance to look under the truck. I think I found the problem. Unless there is suppose to be a vent hole on the bottom side of the rear seal, I have a leak there.

I was looking and there is no fluid on the sides of the transfer case or anywhere forward of where the fill plug is. It

**TurboDiverArt** · 05-02-2006, 12:28

Originally Posted by DA BIG ONE

Art, The front seal does last awhile because there is only rotational movement. However, the back one can leak as early as 30k without off road treks, sooner if you get mud on yoke and it dries.

The tailshaft seal is no biggie, buy the replacement first so you have a better understanding of its extra bellows (useless IMHO). Replacement parts are not too overly priced, and the case rear is available because of the wear through problems on older models, word has it that in 99 production only updated units were used. I beat mine more than average subjecting it to the hot as hell desert, the subtropics, then some flood water for good measure.

Only thing I don't like is that no aftermarket tranny controller can be had because of the autotrac, but all the plus features offset this one big issue.

Thanks for the info!! I'll try to pick one up tonight. I assume it just taps in like older 2WD rear seals? Getting it out is easiest with a small screwdriver and gently taping it in between the case and edge of seal ring, then prying around?

Bellow's, is that what you call it? Looked like a balloon to me....

Art.

**AndyL** · 05-02-2006, 16:41

Originally Posted by MJEasly

Did she notice anything before the chain let go? My case is making a strange noise that changes with road speed. Sounds a lot like a chain rubbing inside the case or a badly lubed chain.

I would also like to know if there are any upgrade kits for this tcase. Seems like a lot of fluid drips out the back of the seal. IIRC, there is a manufacturer that makes a slip-yoke eliminator for certain cases, but not for this one.

Yes, it started vibrating (fairly bad) at about 70MPH, any faster or slower it was fine. Then the chain blew out the backside of the case! Maybe 100 miles between the time it started vibrating till the time it came apart.

**MJEasly** · 05-02-2006, 21:18

Originally Posted by AndyL

Yes, it started vibrating (fairly bad) at about 70MPH, any faster or slower it was fine. Then the chain blew out the backside of the case! Maybe 100 miles between the time it started vibrating till the time it came apart.

Did you ever determine the cause of the failure (e.g., worn chain, low fluid, etc...)?

I have my truck parked right now because I certainly do not want to throw a chain. I'll go over it again to see if I missed anything.

**AndyL** · 05-07-2006, 14:13

Originally Posted by MJEasly

Did you ever determine the cause of the failure (e.g., worn chain, low fluid, etc...)?

I have my truck parked right now because I certainly do not want to throw a chain. I'll go over it again to see if I missed anything.

Don't really know for sure, but it appears that maybe NV forgot (says the rumor mill) to install some of the chain cog retaining clips. My best guess was that my case was missing one (can't remember which cog) clip that allowed that side to wander back and forth on the splins, or in mine, towards the back of the case slowing wearing it thinner and thinner. On our trip to Florida is must have finally penatrated through the back allowing all of the fluid to leak out! From that point it was only a matter of time till it gernaded!

**TurboDiverArt** · 05-11-2006, 12:13

OK, well I

Thread: Can Synthetic ATF be a substitute for GM Automatic Transfer Case Fluid?

Thread Tools

Display

Can Synthetic ATF be a substitute for GM Automatic Transfer Case Fluid?

Your ?

syn.in the trannsfer

Fluid use

Questions

Updates

Seal?

Posting Permissions