Transfer Case Fluid Change time 99 Blzr

I am getting ready to change out the fluid on my transfer case and ran across this TSB. So do we put in Autotrac or Dexron III ????

I am thinking that since it is an automatic transfer case it's AutoTrak fluid.....

99 Blazer LS 4-button setup...2HI, 4HI, 4LO, 4-Auto....


Transfer Case - Improved Automatic Transfer Case Fluid

File In Section: 04 - Driveline Axle

Bulletin No.: 99-04-21-006

Date: September, 1999

INFORMATION

Subject:
Improved Automatic Transfer Case Fluid

Models:
1999-2000 Cadillac Escalade
1998-2000 Chevrolet and GMC K/T 4-Wheel Drive Pickups and Utility Models
1999-2000 Chevrolet and GMC L Van Models
1999-2000 Oldsmobile Bravada
with Active Transfer Case (RPOs NP4, NP8)

Effective with vehicle production in late June of 1999, all active transfer cases on the above listed vehicles have been filled with Autotrak(R) II fluid, P/N 12378508 (P/N 10953626 in Canada). This fluid is a light blue color rather than the red color of the previous fluids and is the next generation Automatic Transfer Case Fluid. The fluid also contains a better friction modifier. On the models listed above, the active transfer cases should only be serviced using P/N 12378508 (P/N 10953626 in Canada), even if the original fluid was the red Autotrak(R) fluid. The previous fluid and the new fluid can be mixed or topped off if necessary. The new Autotrak(R) II fluid will be the only available fluid once the supply of the old red Autotrak(R) fluid is exhausted on units older than stated above.

The Owner's Manuals and some service information will specify the incorrect fluid due to printing the information prior to the fluid change being introduced.

Parts Information

Parts are currently available from GMSPO.

'99 and on saw a revised clutch pack in many NP electronically controlled transfer cases and AWD center differentials. There is absolutely no harm in putting Alltrak II (blue synthetic fluid) into an older NP transfer case, wether it is electronically controlled or manual shift (like mine). However, draining the blue and putting Dextron III back in can be detrimental.

The clutch pack revision actually ADDED more clutches and discs for a more robust transfer case, but it became a tad sensitive to the fluid friction modifier/additive pack present in Dex-III. Dex-III also does not hold up well to the friction and heat these revised transfer cases generate, deteriorating Dex-III into coke and sludge in under 500 miles of normal driving.

There is no harm in going to Alltrak-II in your application, it's actually a superior fluid for the transfer case. It's what's sloshing in mine at the moment though it does not require it. However, never, never, EVER put Alltrak-II in your automatic tranny either.

Thanks for the info ... have not actually drained my TRF C yet, but the dealership say that with the Active transer case and Automatic that Autotrak is what I want....

So 2.5 quarts so I bought 3 @ $5.50 each and will be ready to go this evening or so....

I will pull the fill plug first and check to see what's there, but will drain and put autotrak in...

...and no I will leave the tranny flushing / service for the shops as I don't want to mess with it....Bet autotrak would wreak havoc eh ?

Yeah, it's a completely revised fluid, and though superior in every way to Dextron-III in *Transfer Case* application, it totally screws up bands, clutch plates etc. in an automatic tranny. It just struck me odd for years how almost everyone else uses a GL rated gear lube in their transfer cases. Jeep (AMC Jeep that is) Chevy in the good old days, Ford, etc., etc., in the past would fill the X-fer case with the same glop you filled your axle pumpkins with. But then, the designs of the older x-fer cases were quite different and quite simple then too.

Least near as I can figure, even a crappy Dextron formulation (Supertech Walmart 1-gallon jugs anyone? *shiver*) is a GL rated fluid, but obviously much, much thinner. (GL-3 Comes to mind for some odd reason) Perhaps the better, tighter precision made designs did not require such a thick fluid to cover up noises and protect surfaces. The thinner fluid also moves, climbs and pumps easier, possibly saving on fuel consumption in the overall design. But dollars to donuts in this case, the reason why Dextron-III was specified in the older NP-2 Manual and electric shift modules before '99 was because they do have clutch packs similar to those in your auto tranny. They have to be kept clean, cool, and in a friction modified environment so that they grip when needed, slip under stress to keep your driveline from getting hammered into goo and twisted steel. Those are my thoughts and reasoning near as I can figure why it's there in the first place. Anyone else with more certain knowlege is more than welcome to add anything helpful!

Well I changed the transfer-case fluid on my NP-236 2-speed auto transfer case. Interestingly, the red auto trak came out was expecting blue as I had my tranny overhauled (sun shell reaction assy) about 50K+ miles ago.

The care was built in Jan-99 and have never had one problem with 4 wheel drive system...but was into my maintenance process for the summer and decided the driveline was going to get attention.

I put 2 full quarts of AutotrakII (the blue fluid) and gave it a test drive....shifted through all the selections and all worked fine and seems to run a bit smoother.

So all is well and it now has the new fluid in....

I guess you could call this a "Liquid Upgrade"... :biggrin:

Now if they could only bottle up a 22 PSI super charger I could just add to my engine oil... :D