Hi All,
A few months ago I replaced the transmission and Tcase in my 98 Olds Bravada. I swapped the NP233 into it during the procedure. About 1 month later the Tcase grenaded! What a noise! Split the case and everything. I drove it home with the tattered driveline hanging under the car. So I swapped the 136 back in to make the car driveable while rebuilding the 233. Found the problem to be the stupid little vacuum valve that had allowed the engine to suck all the fluid out of the tcase. A $5 part that blew the whole works!

Anyway, after swapping the 136 back in it started leaking badly after a week or two. I had to add about 1 qt of trans fluid every week until I finished with the the 233. Now I am in the process of swapping it back in and when I pulled the 136, I found the source of the leak. The damn adapter cracked near the top bolt on the driverside. This had happened with the original Tcase and transmission and I found it while swapping the transmission. So now I have broken the adapter two times!

Obviously I cant put the 233 in without replacing the adapter, but there are two available from GM. **028096 (M30,NP1,NP4,ZM6,ZQ1,ZW7,Z83,Z85) and **028097 (M30,NP1,ZR2). The first part number does report to my VIN, but I am wondering if maybe the ZR2 adapter might be stronger? I can find no detailed info on this anywhere and pictures of the transfer case for ZR2 and NP4 opcode vehicles on EBAY show no obvious difference between the two (same ribbing, etc.).

On a different forum for ZR2s it sounded like the 2-door version of the Blazer might have had a shorter adapter and input gear on the 233. So that would mean that the main difference is length of the adapter, but since I dont want to pull the 233 apart to change the input shaft/gear, I would just get the correct unit if this is the case.

Car is on stands and I need to order this part. Does anybody know what the differences between the two adapters might be? The ZR2 part is a 1 day ship and the NP4 is a 3 day ship, so I would rather get the ZR2 part anyway (if it isnt shorter).

Thanks!
-William

 

i would say there is no difference. no reason to be. even the adapter on my full size truck is same width, as my blazer, just different tcase bolt pattern.

the only time the adapter changed was between first gen and 2nd gen.

 

Well GM cant tell me what the difference is... Ill keep an eye out for the casting numbers the next time I see a 2-door with the drivetrain still in it in the junk yards. After talking to about 20 junk yards and several transmission shops I found that the best place to get one of these things quickly is actually a transmission shop. They are very familiar with the problem. Junk yards only wanted to sell the adapter with a tcase or transmission.

One of the transmission shops said that the first adapter probably broke because of a sticking U-joint, which I fixed prior to the first time this thing failed. Then the second one was probably weakened by the transfer case blowing up. According to that transmission specialist, he has never seen one of these break without one of three things happening.
1) trans mount completely shot
2) U-joints frozen or sticking
3) Tcase damage.

So now that my U-joints are all brand new and my Tcase is rebuilt, HOPEFULLY I can put this thing back on 4 tires for more than 2 months! 274K and counting...

-William

 

why not just order both from the dealer and bring the origional when you
go to pick up the part and compair which one matches the origional, then only purchace that one and refund the second one?? dont forget the paper gaskets that go along with the adapter