Hello everyone, technically I am new to the forum but in all honesty I have come here for all of my blazer questions in the past, I have owned 1 jimmy and 3 blazers. So thank you all first and foremost, im now officially a member, anyways....

I have a 98 blazer zr2. the transfer case is a np233c. i ordered another transfer case because i believe its shot. reason being, the 2 hi, 4 hi, and 4 low all work, problem is, is when i have it in 4 hi or low, there is a clunking noise. as i speed up, it speeds up, and it doesnt get worse when i turn. the cv axles are fine. i removed the front shaft and had it on stands, the sound was a lot quieter but it was still there so i believe it is the transfer case that is busted, i dont know if anyone has any insight or had the same issue.

unless anyone knows what it could be, im going to replace it completely and i dont know what fluid to use. i have seen some people say synthetic 75w-90 and others say to use the GM performance auto trak II fluid. Any help would be much appreciated. The transfer case should arrive by the weekend or early next week so if there is any chance that it isnt a goner, i'd rather find out before i install it. THANK YOU ALL!

 

You can't put just put plain gear oil in it. The Auto Trak II stuff is what you want. That oil weight works well in the "pumpkins"

 

thank you much, thats what i figured. from what i understand the recommended Dexron III is discontinued so the auto trak II stuff is what to use instead, and i guess its better.

 

Just a quick note for other readers of this threrad. Many of the 98+ ZR2 pickups do NOT use Autotrak II, but use ATF (now Dexron VI) in the transfer case.

You should always do a VIN cross reference for what fluid from the dealer or FSM when selecting fluids for Blazer, Jummy, Bravada, S10 etc.

 

ATF for the 3-button, 2-button (1st gen), & manually shifted t-cases. Autotrak-II for the 4-button & AWD t-cases. Don't use gear oil!