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

**AndyL** · 05-12-2006, 14:55

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** · 05-14-2006, 19:21

Originally Posted by 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!

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** · 05-24-2006, 12:35

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** · 05-24-2006, 14:52

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** · 05-24-2006, 15:18

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** · 05-24-2006, 18:17

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** · 05-25-2006, 08:50

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.

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** · 05-25-2006, 09:14

Originally Posted by curmudge1

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** · 05-25-2006, 10:20

Don't know if the Transfer Case leak 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** · 05-25-2006, 15:57

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** · 05-25-2006, 16:56

Originally Posted by 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.

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** · 05-26-2006, 01:29

Originally Posted by TurboDiverArt

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** · 05-26-2006, 02:52

Originally Posted by DA BIG ONE

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** · 06-12-2006, 07:20

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** · 06-12-2006, 08:17

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** · 06-12-2006, 16:47

Originally Posted by 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.

Just PM'd you.

**DA BIG ONE** · 06-14-2006, 02:50

Originally Posted by TurboDiverArt

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** · 06-15-2006, 03:29

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** · 02-02-2008, 18:14

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** · 02-03-2008, 04:34

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.

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

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Case leak

Amsoil says that, too

NP 246 lube/fluid

Clutch?

I found the leak!

Hole

Glad to have helped ya!

Suspect his case had casting flaw

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