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

[TurboDiverArt]

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]

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]

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]

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

[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.

[DA BIG ONE]

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/transfercasesparts.html#New%20Process%20Model%2024 6

http://www.omegamachine.com/html/New_Process_246_seal_installer.html

[TurboDiverArt]

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/transfercasesparts.html#New%20Process%20Model%2024 6

http://www.omegamachine.com/html/New_Process_246_seal_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]

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]

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]

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. :rolleyes: 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]

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]

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]

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]

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]

[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. :rolleyes: 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]

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]

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]

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]

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]

OK, well I

[AndyL]

Art,

As in my case the chain grinded all the way through the case on the top rear near the tail shaft. If you are hearing noise it could definatly be the chain rubbing. At your point it could just be a hair line crack, almost totally unnoticable!

[TurboDiverArt]

Art,

As in my case the chain grinded all the way through the case on the top rear near the tail shaft. If you are hearing noise it could definatly be the chain rubbing. At your point it could just be a hair line crack, almost totally unnoticable!
Guess the bulletin board never sent me the notification email as I'm just seeing this now. I only get noise when the fluid is really low. It has not made noise in a week since I replaced the seal and added fluid. I need to look closer but it doesn't seem to be leaking anymore. Not sure exactly what that means. I'll let it go another week and then check the fluid level.

Thanks,
Art.

[TurboDiverArt]

Well after being completely frustrated with this damn leak I took drastic measures. I have tried replacing the tail seal on the transfer case and that didn

[DA BIG ONE]

Art, sorry to hear your still having trouble w/t-case. The rear case half can be bought along with chain, clutches, steels, etc., bit less than a rebuilt if you have the time and knowhow.

When I changed out my NP246 it was because of the tow shop towing it in gear which resulted in damaged t-case.

New NP 246 can be had for just under $1,000. consider this is about 1/3rd of what dealer charges.

[AndyL]

Art, you would have to change the output shaft on the tranny as well, which requires a complete tear down! And then a new driveshaft!

[TurboDiverArt]

I was really being tongue and cheek about converting it to 2WD.

I've rebuilt more transmissions in my racecar than I care to talk about. Maybe I'll get through this season with just one.... The actual rebuilding or installation of a new transfer case doesn't worry me too much. It

[curmudge1]

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.

I was looking on Amsoil's web site for Synthetic ATF for my 99 Tahoe 4wd (5.7gas) and it said their Syn ATFs were for OTHER THAN AUTOTRAC transfer cases, to use the GM fluid for that one. Guess Amsoil doesn't want to get in the middle of GM's problems for the 99s (other years, too?)?

Have to keep a close eye on that transfer case I guess.
--
Dave in NJ

[TurboDiverArt]

I was looking on Amsoil's web site for Synthetic ATF for my 99 Tahoe 4wd (5.7gas) and it said their Syn ATFs were for OTHER THAN AUTOTRAC transfer cases, to use the GM fluid for that one. Guess Amsoil doesn't want to get in the middle of GM's problems for the 99s (other years, too?)?

Have to keep a close eye on that transfer case I guess.
--
Dave in NJ
I believe both Red Line and Royal Purple list their fluid being a replacement for the auto track fluid.

Where in NJ are you? I'm in Edison.

Art.

[More Power]

Don't know if the Transfer Case leak (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=18589) problem experienced by some of the newer trucks is related to the leaks discussed here, but the link will take you a forum thread that shows what is causing those leaks.

Jim

[DA BIG ONE]

The guys that sell the NP246 new & rebuilt call for synthetic fluid to be used.
Doubtful GM's blue stuff is any better, but it sure cost's like it is. I'm running B&M's best synthetic so far no issues.

Remember this t-case has 9 clutches and 10 steels which help absorb the shock when front and rear shafts are at different speeds in auto 4wd.

[TurboDiverArt]

The guys that sell the NP246 new & rebuilt call for synthetic fluid to be used.
Doubtful GM's blue stuff is any better, but it sure cost's like it is. I'm running B&M's best synthetic so far no issues.

Remember this t-case has 9 clutches and 10 steels which help absorb the shock when front and rear shafts are at different speeds in auto 4wd.
Something that sort of puzzles me but I think I'll be able to answer it myself is this. I always assumed the transfer case used clutches to engage 4WD as well as "LO" gearing. If it's using clutches, why is there a chain? Is the chain what transfers power from the main shaft that I assume drives the rear wheel to the front drive shaft? I would have thought it would have been a locking gear that did this but I know there is a chain in there somewhere.

Additionally, are clutches used in auto 4WD to stop and start power delivery to the front differential or is the locking and un-locking done in the front differential? My assumption is that it

[DA BIG ONE]

Something that sort of puzzles me but I think I'll be able to answer it myself is this. I always assumed the transfer case used clutches to engage 4WD as well as "LO" gearing. If it's using clutches, why is there a chain? Is the chain what transfers power from the main shaft that I assume drives the rear wheel to the front drive shaft? I would have thought it would have been a locking gear that did this but I know there is a chain in there somewhere.

Additionally, are clutches used in auto 4WD to stop and start power delivery to the front differential or is the locking and un-locking done in the front differential? My assumption is that it’s in the transfer case. The front hub probably disconnects in 2WD but is locked in 4WD and Auto 4WD. Hence the reason you get worse mileage in Auto 4WD even though it’s not engaging on dry pavement.

Art.

The clutch is always engaged, the encoder motor adjusts the amount of clutch pressure using input from the ems, abs, along w/frt/rear drive shaft speeds in Auto 4wd only, otherwise the clutch is fully engaged unless in neutral. W/o clutch pack and pressure control of encoder motor in auto 4wd there would be shock waves from engaging/dis-engaging affecting drivetrain to the point of something breaking.

With autotrac front driveshaft rotates always "but does not drive the frt/diff inless in a 4wd range", when shifted into any 4wd range the front differential engages locking the frt/differential to driveshaft power through t-case would be direct in in 4wd hi/lo but controlled in auto 4wd. The front diff carrier is of the open design.

[TurboDiverArt]

The clutch is always engaged, the encoder motor adjusts the amount of clutch pressure using input from the ems, abs, along w/frt/rear drive shaft speeds in Auto 4wd only, otherwise the clutch is fully engaged unless in neutral. W/o clutch pack and pressure control of encoder motor in auto 4wd there would be shock waves from engaging/dis-engaging affecting drivetrain to the point of something breaking.

With autotrac front driveshaft rotates always "but does not drive the frt/diff inless in a 4wd range", when shifted into any 4wd range the front differential engages locking the frt/differential to driveshaft power through t-case would be direct in in 4wd hi/lo but controlled in auto 4wd. The front diff carrier is of the open design.
Ahhh, that makes sense now, thanks!!

[TurboDiverArt]

Well, I found where the leak is coming from. I have found a small hole in the rear tail shaft housing. It doesn

[DA BIG ONE]

Only speedo pickup behind there, maybe just a casting flaw. The clutch/plate assembly is on the other side forward of the chain.

Thinking you maybe ok w/your fix!

PM me your e-mail I'll send a drawing of the t-case internals.

[TurboDiverArt]

Only speedo pickup behind there, maybe just a casting flaw. The clutch/plate assembly is on the other side forward of the chain.

Thinking you maybe ok w/your fix!

PM me your e-mail I'll send a drawing of the t-case internals.
Just PM'd you.

[DA BIG ONE]

Just PM'd you.

When I paid to have repairs done I could have cared less that I knew little, or nothing. Since getting burned more than a few times by so-called certified repair shops I've been in a learning curve w/this burb and have collected lots of info not available in repair manuals.

The diesel page has helped big time.....

Again, good luck.

[TurboDiverArt]

Well it's been a couple of days and no leaks, at least 100 miles. I cleaned the hole and scuffed the area real well. I put JB weld on the area and covered it pretty good. Actually three coats. The first one I put on when the transfer case was warm. That was a mistake as the JB weld became liquidy. It did get in the hole real well. I subsequently coated the area two more times. So far so good. Going on vacation next week so I'll be putting on an additional 500 miles so that will be a good test. Thanks for all the help, TDP is great.

Art.

[HammerWerf]

Art,

Been a year and a half since your repair. Still holding? I hope so. as I may be looking for a similar leak.

HammerWerf

[DA BIG ONE]

The NP 246 AutoTrac is a good stout unit not suffering the issues of wear through other t-cases have had.

However, when my NP 246 had to be replaced it was because of a tow truck operator who swore he knew what he was doing, "he didn't", when he had to pay for the t-case replacement then he really knew! Towed the truck w/o placing the t-case in neutral which quickly damaged unit. Factory NP engineers were the ones to report to me that a good synthetic fluid is good to use in the NP-246, so far, so good.

I'd like to get a report too.

[TurboDiverArt]

Art,

Been a year and a half since your repair. Still holding? I hope so. as I may be looking for a similar leak.

HammerWerf

Yup, still holding. Each time I change the oil I take a peek at the glob of JB Weld and it's still not leaking. I'm very pleased to say the least!

Art.

[TurboDiverArt]

The NP 246 AutoTrac is a good stout unit not suffering the issues of wear through other t-cases have had.

However, when my NP 246 had to be replaced it was because of a tow truck operator who swore he knew what he was doing, "he didn't", when he had to pay for the t-case replacement then he really knew! Towed the truck w/o placing the t-case in neutral which quickly damaged unit. Factory NP engineers were the ones to report to me that a good synthetic fluid is good to use in the NP-246, so far, so good.

I'd like to get a report too.

I remember reading in the owner’s manual when I got the truck about needing to put it in neutral before towing. I always wondered if it was BS, now I know it is indeed true!

Art.