Auto transfer case maintenance

I originally posted here a few months ago with a blown transfer case in a '96 Bravada. I got a pile of good advice and got the Olds running right and sold it. Now I am driving a '99 Jimmy with the "Auto 4 WD" button to the left of the regular "4WD HI" button. Does this TC need the fluid swap program that was recommended for the AWD TC's? Mileage is at about 86 or 87K.

Yes don't fall into the trap I did. The manual never mentoned the transfer case. Had I known I would have changed the fluid on the same schedule as the transmission. From what I understand this transfer case (New Process 236) uses a special fluid available only at the dealer. The original fluid was red now it is blue. Your manual will list the old part number. Expect to pay about $7.00 a quart or more you will need 3 quarts.
I got 96,000 on my Jimmy with the auto 4WD and now the thing is stuck in 2HI. I never serviced the transfer case even though the truck was dealer serviced every 3000 miles! The dealer never mentioned the transfer case and its not in the manual. I followed the heavy duty maintenance schedule to the letter. They wanted to clean my spark plugs every 36,000 though and thats not in the manual either!

The light blue fluid is called AllTrack-II synthetic fluid P/N 12378508 and it should hold exactly 2 qts per my 01 owners manual and I did my 99 and it was 2 - but the 99 said Dextron III so after reading your post my searches turned up that GM printed the 99 manuals before AllTrack fluid came out and if I don't put it in (now at 120k) I'm probably screwed (already I bet)! The newer fluid has friction moderfiers in it due to the clutch packs in the Autotrac transfer case and GM was having problems with them - big surprise there! I've got a page on transfer case/4wd operations on 2nd gen Blazers almost written up that I will post soon so we all can understand the system and fluids - lots of wrong stuff out there but this forum has given more correct info than most other sites doing full google searches!

It depends on what transfer case.
136-236-246 transfer cases all call for the special fluid.
Figure out or check what transfer case you have and then check the owners manual or a good service manual.
MT

My manual calls for Dexron.The dealer parts manager and my neighbor who is a retired Olds tech said to use the Alltrak ll. The parts guy said that if the vehicle has buttons on the dash they use blue stuff (Alltrak). If it has a handle on the floor it gets red stuff (Dexron). My neighbor says the blue was developed as a fix for sticky TC's in the early 2000 and newer cars, and service bulletins were sent out advising how to use it to fix binding problems. He says there were no bulletins for older cars because GM doesn't care about them. Since there is no warranty liability with older cars, GM would just as soon see you have to replace these TC's than get them working right. He said they used it in older cars to fix binding issues successfully. I'm swapping mine out for the blue tomorrow, before I get problems. I had the auto 4wd on the other night in the rain and when I dropped off the guy that rides with me the thing chattered pretty bad when I turned around in the semi-dry parking lot. My original post on the old Bravada describes these problems and has good advice for getting them straightened out. If I can find it I'll put up a link.

http://www.automotiveforums.com/vbulletin/showthread.php?t=426615

This thread shows the problems I was having with the old Bravada. I paid $36 for 4 quarts of fluid at my local Chevy dealer. The outside of the bottle says something about using it in vehicles according to owners and service manuals and as described in various service bulletins. The guy says if it comes out blue just change it once and bring 2 back. I also found threads about bulletins on these TC's in the Astro Forum. They cover 99 thru 2003 TC's.

http://www.automotiveforums.com/vbulletin/showthread.php?t=426615

This thread shows the problems I was having with the old Bravada. I paid $36 for 4 quarts of fluid at my local Chevy dealer. The outside of the bottle says something about using it in vehicles according to owners and service manuals and as described in various service bulletins. The guy says if it comes out blue just change it once and bring 2 back. I also found threads about bulletins on these TC's in the Astro Forum. They cover 99 thru 2003 TC's.

It all depends on what transfer case you have.
What transfer case do you have?
MT

NP 236 CM, don't hold me to the CM the tag is banged up. It had red in it, and a tag calling for Dexron lll. I filled it with blue, drove around for a half hour, drained it and refilled with blue. It still chirps in a tight turn with the Auto 4wd on. I guess I'll do the differentials with synthetic gear lube next.

heres another one of my dumb questions :shakehead , what is the difference between the regular transfer case and the auto transfer case? Is it all wheel drive when u hit the auto 4wd button? im a little confused :confused: i ask because im thinking about getting a newer blazer/jimmy, silverado/sierra, or tahoe/yukon. most of the pickups or tahoes/yukons that are 4x4 have this button and i just wanted to know more about it.

NP 236 CM, don't hold me to the CM the tag is banged up. It had red in it, and a tag calling for Dexron lll. I filled it with blue, drove around for a half hour, drained it and refilled with blue. It still chirps in a tight turn with the Auto 4wd on. I guess I'll do the differentials with synthetic gear lube next.

The 99 gmc jimmy 236 calls for the blue gm fluid.
In auto mode the front axels/drive shaft should not engage unless the rear wheels are slipping.
You may need to drive it a while for the blue fluid to start working.
Are you sure the transfer case has not been replaced or switched?
If it keeps on doing it get a good scanner on it and check out the transfer case operation. If it has any problems it should show pp on a good scanner that can read transmission/transfer case and body codes and data.
Also most good scanners have some test you can run on it.
If it shows any B or C codes post back code no.
MT

heres another one of my dumb questions :shakehead , what is the difference between the regular transfer case and the auto transfer case? Is it all wheel drive when u hit the auto 4wd button? im a little confused :confused: i ask because im thinking about getting a newer blazer/jimmy, silverado/sierra, or tahoe/yukon. most of the pickups or tahoes/yukons that are 4x4 have this button and i just wanted to know more about it.

The 236 auto transfer case is a automatic/electronic controled 4 wheel drive in auto mode.
In auto mode it only pulls on rear wheels unless they start slipping then it applies power to the front wheels as needed.
The old floor shift ones are manual shifted in or out of 4 wheel.
Then you have the all wheel drive jobs. 4 wheel all time.
On them the pull is mosty but not all together on rear wheels and if rear wheels start slipping they transfer more power to front wheels.
Kinda of a variable 4 wheel drive. All done with a viscious clutch inside the transfer case
MT

so its basically like all wheel drive on demand. alright thanks for clearing that up MT.

so its basically like all wheel drive on demand. alright thanks for clearing that up MT.

You are welcome.
And 10-4 on the 4 wheel on demand. It just kicks in when you need it.
Which is a good deal as long as it works right and be sure to use the blue GM fluid to keep it working right.
MT

The manual calls for GM Part # 12378396. A tag on the TC says NP 236, and a seperate tag calls for the same product to be used in the transfer case. That part number is Dexron lll. The TC has a manufacture date of 1998. The vehicle went into service in Oct. 1998. I have to assume this is the original TC. I used GM part no. 12375808. I can't put my finger on an official document from GM saying I should have done this, but everything I've heard or read indicates that these TC's need to have this fluid in them. I think the point of this whole discussion is that if your automatic transfer case does not have this improved fluid in it you should get it in ASAP. I've read Bulletins calling for this fluid exchange on Asrtos, Caddies, Bravadas and other vehicles from model year 1999 to 2003. I think I've done the right thing. MT do you agree?

The manuals were printed before GM came out with the blue fluid to fix the AWD and Autotrac transfer cases failing in 99 (mainly in AWD due to always on). The dealers are kinda clueless on this - the improved fluid should be able to be run in any case would be my opinion. This blue syn fluid was to solve clutch binding and wear and added friction modifiers per GM. The only risk I have read about on all syn fluids is long term RTV breakdown and this mainly applies to rear ends with no gasket, only RTV.

So do I need to take my car to a stealership to get it serviced? or can I just get the fluid and take it elsewhere. I just crossed 124k miles and it has never been changed so I am prolly in deep doo doo.

The manual calls for GM Part # 12378396. A tag on the TC says NP 236, and a seperate tag calls for the same product to be used in the transfer case. That part number is Dexron lll. The TC has a manufacture date of 1998. The vehicle went into service in Oct. 1998. I have to assume this is the original TC. I used GM part no. 12375808. I can't put my finger on an official document from GM saying I should have done this, but everything I've heard or read indicates that these TC's need to have this fluid in them. I think the point of this whole discussion is that if your automatic transfer case does not have this improved fluid in it you should get it in ASAP. I've read Bulletins calling for this fluid exchange on Asrtos, Caddies, Bravadas and other vehicles from model year 1999 to 2003. I think I've done the right thing. MT do you agree?

Yes 10-4 on the blue 12375808 GM transfer case fluid.
All of the info I have says to use the blue 12375808 GM fluid in a 236 auto transfer case. Even several years older.
Also it should be change on a regular basic.
There may have been some tsb out on it but not sure.
Good luck and drive it a while and see if it starts working better.
MT

So do I need to take my car to a stealership to get it serviced? or can I just get the fluid and take it elsewhere. I just crossed 124k miles and it has never been changed so I am prolly in deep doo doo.

Ever hear of the magnusson-moss law?
Do some research on it.


How ever the dealer will have you over the barrel on the GM fluid 12375808 transfer case fluid. But you can buy it from the dealer parts department and put it in at a place of your choice or do it yourself.

The info below pertains to chips but holds true on aftermarket parts.

You won't void his warranty. Dealers try to pull that "void your warranty" crap all the time & they LOSE in court or arbitration unless they can PROVE that the particular modification or aftermarket part caused a covered part to fail. Check out the Magnusson-Moss Warranty Act for specific info.
Also, according to Hypertech's Web site, the Power Programmer for the '04-'06 Silverado is CARB approved. The EPA recognizes CARB approval as meeting EPA standards as well, so you wouldn't be in violation of the Clean Air Act if you had reprogrammed his speedo to compensate for the big gears & big tires.
From Hypertech's Web Site:
All Hypertech Power Tuning products are legal for sale or use on California pollution-controlled motor vehicles according to CARB Executive Orders. Power Tuning products for 1998-2004 Ford and Chrysler gasoline, as well as Dodge Cummins diesel applications, are currently in approval-pending status, based on completion of required testing presently being conducted. All 2004 and prior Ford Power Stroke and all GM Duramax applications are legal for sale or use on California pollution-controlled motor vehicles under CARB E.O. D-260-10 and D-260-11, respectively.
In the interest of improved air quality, the California Air Resources Board (CARB) requires new vehicle and manufacturers of aftermarket parts to develop engine and emissions equipment that either reduce or maintain specific air pollutants affected by vehicle use. Both the California Vehicle Code (section 27156) and Federal Clean Air Act (administered by the Environmental Protection Agency) prohibit modifications that increase vehicle emissions. Aftermarket parts manufacturers, particularly in the high-performance segment, are required to obtain CARB approval in the form of executive Orders (E.O.s) for any product not qualifying as a direct replacement for an original equipment part. Hypertech includes meeting all E.O. requirements in its product development process. This guarantees that users of Hypertech "Power Tuning" products will meet certification requirements when registering, selling, or needing to pass various emissions tests or Inspection and Maintenance (I and M) programs administered by state or local enforcement agencies. Make sure that any emissions-related product you buy and install carries an E.O. number or is pending an E.O. Without this verification you are at risk, in potential violation of regulations and may incur unnecessary financial obligations during vehicle inspections or emissions tests.

CS, this is a pretty straightforward process. I bought a pump for on a gallon jug at Advance Auto for $4. Go to the dealer and ask for 4 quarts of the 12375808 juice, it will run about $30. I ran the car up on ramps and crawled under and pulled out the bottom plug. The plugs are located on the lower back of the transfer case. Drain the TC into your oil change pan. I put 2 quarts of the new stuff into a clean antifreeze jug and put the pump on. I pulled the top plug and replaced the bottom plug. Stick the hose from the pump into the top hole in the TC, pump the juice in until it runs out the top and put the plug back in. On the ramps mine held almost exactly 2 quarts. Button everything up and drive around for a half hour or so. Go down some winding roads and into a parking lot or 2. Have the auto 4wd on and put it into and out of 4wd a few times in the parking lot. Don't really stress anything just work it out a little. Go back and drain out the fluid and replace it again. You are done. If you have blue in it when you pull the plug just change it once and take 2 quarts back to the dealer.

I believe that the Blue Smurf Oil does not stay blue when it is spent.

I have a '01 Suburban 3/4. Has AutoTrac II TC. The clutch burned up. Fluid was dark. Stealers replaced TC. 4 months later with approx 100 miles of 4x4 in the sand and a few miles on mountian terrian 4x4 does not pull in reverse and seems to not pull as much as it used to after the TC was replaced. Defective? I smell a slight odd burning odor. I'm about sick of this Autotrac Crap! Granted my Sub is Supercharged via Whipple. Do you think the whipple is eating the TC?