The smarttrak in 98 plus vehicles works great. It is not meant for off roading, it is meant for better stability on pavement containing rain or snow.

On The 98+ Bravada, the following should be done every year to keep the AWD in top shape and prevent expensive repairs:

Change the transfer case fluid, make sure it is the blue autotrac II. If it is the first time, drive 500 miles and change the fluid again. Then annually.

Change the front transaxle and rear differential fluid (same stuff) to a high quality synthetic fluid, Then anually

Update the transmission fluid to Dextron VI. Then change annually,

Do the above and your AWD system will work like a charm for a very long time. Don't, and you will have premature failure of your drivetrain.

 

GunsOfNavarone (or anyone with this info)
I just got a 2001 Bravada with the usual Smartrac, NP136, etc... It's working fine, but at 88K and 11 years old, it's probably time to do some preventative maintenance.

Looking at the service records:
-a new rear transfer seal was installed in March of 2007. 21K miles ago.
-in March of 2009 (10K miles ago) a tranny overhaul was done due to sheared splines. This shows a 2 quart transfer case fluid change (GM 12378508 Auto Trak II) as well as the obvious ATF fluid change with 16 qts of Dex VI (GM 88861003).
I see no other drive train work done in the service history.

Seems that since this has never been done, it is high time to change out the fluids in the front transaxle and rear differential.

Question 1:
How much fluid/oil is needed to change out both the front transaxle and rear diff? I don't mind shelling out for the synthetic 75W90 that I assume works for both. Does this vehicle have both drain and fill plugs or do I have to pull the covers?

Question 2:
With nearly 4 years and 10K miles (pretty much all slower, in town driving by old people) since that was done, does it make sense to do another fluid change on the transfer box and tranny? Again, it all seems to be running fine, but am wanting to keep it that way. I am leaning on the side of a fluid change, but want to hear what y'all think.

I am open to all opinions and suggestions.