I have a 2000 Blazer selectable 4x4 system, son just wrecked it last weekend, I picked up a 1999 Bravada with the auto 4x4 system and a bad motor, so I'm going to be installing the motor from the Blazer into the Bravada. My question is, has anyone swapped out the auto system for the manual? The Bravada needs a t-case and since the blazers powertrain is good, it would save me money on parts. Thanks for any help in advance. Nick

 

The motor will swap directly over without any issues.

The swap to the NV233 transfer case from the NV136 will be much more involved. You will likely have to change over the wiring harness both inside the truck and underneath to get the proper connections for the TCCM, 4wd switch in the dash, and the transfer case itself. You will very likely have to get your PCM reprogrammed to add the proper shift tables for low range operation as well.

What makes you think that the NV136 transfer case is bad?

If it is engaging too often, it likely is a fluid condition issue. The NV136 uses GM Autotrak 2 fluid (blue in color) and is required for proper operation of the clutch pack inside. Using regular Dexron III ATF can cause the clutch pack to lock up too quickly causing the drivetrain to bind up while turning on high traction surfaces.

If it isn't engaging the front output at all, then it is possible that it is just the encoder motor on the side of the transfer case not working properly.

Have you had the TCCM scanned for stored trouble codes?

 

We had a customers Bravada in here that the fluid change did not work after a couple flushes, so it was swapped out of this Bravada to fix the other. Now that I bought this one for myself, knowing it binds in turns even after a couple cycles of Auto Trak 2 fluid, I needs to be replaced. Or replace the clutch assy inside. This one came in with a bad motor and now since my son wrecked the good Blazer, I was just going to swap over the good motor into the Bravada. Ever replaced the clutch assy inside the t-case?

 

If the transfer case is sending torque to the front all the time (after 2 AutoTrac II changes), the most likely problem is the actuator motor on the transfer case is frozen in a position that engages the clutch. Usually when the clutch is bad, it is wore out and sends no torque to the front, ever.

IMHO I would pull the actuator off of the TC and test drive to see if the front is still binding next.

 

I'll give that a shot after I get the motor replaced. Not in a big hurry to swap it all over yet. Makes sense tho. And would save a lot of BS. Then I can just part out anything of value on the blazer and call the junk yard to pick up the shell.

 

Do the clutches ever bind up and not allow themselves to slip?

 

Not very likely unless the fluid is really old, very low or wrong type.
It is possible the TC has a mechanical failure that keeps the clutch engaged but the most likely suspect is the actuator itself keeping it engaged. If you remove actuator and it's still messing up (give it a few miles to work the newer fluid into the clutches) then it's likely a rare mechanical failure in the TC.

On my, new to me, 2000 Bravada, 318k miles, the actuator gearing was jammed because of corrosion deforming actuator housing and not allowing it to release after application. I have receipts and appears it was driven this way for over 100k by previous owner and now even though the actuator is working, there is no front engagement, the clutches on mine are worn out I fear.

 

One of my techs said he monitored the switching of the motor through the scan tool, the motor was not pulled out tho and driven. i'll have to wait till I get the engine replaced to check all that.

 

The actuator in the TC has no feedback and the best test is to try and turn it manually, it is normally stiff to turn because of the reduction gearing, If it is froze up. you won't be able to turn it at all. I must be lined up manually with the TC shaft before installing.

If power is applied while off of the TC it will move toward one end of its travel and then stall. It has no reverse action, it is returned to 2WD position by the spring loaded linkage in the TC when installed and operating normally.

Note: these facts only apply to the 1998 an up Bravada, Astro & Safari NV-136.

 

Got motor swapped over this week, pulled off tc actuator motor and no more binding when turning, happy me, now just a new decoder motor and 4x4 will work as it should. thanks for advice.