I have a 98 gmc jimmy slt and i have been trying to fix my 4wd. I am positive that i have an np233 transfer case. I have replaced the dash switch, vacuum actuator, tccm and encoder motor (with known working parts) and my TC still will not shift into 4wd. At this point i believe it is wires or connections between the tccm and the encoder motor that are not connecting correctly and causing my problem.

I'm just want to know if anyone else knows of anything else that could be the problem.

Also in replacing the encoder motor I had to remove the front drive shaft and in that process the snap ring broke. I have been searching EVERYWHERE for this snap ring. My problem is that every time i find an exploded view of the np233 (to see if i can find a part number) it shows that the front output has a yoke while my TC has a slip shaft (just like the main output).

Any knowledge about where i could find this snap ring?

Thanks

Picture 1 shows my transfer case

Picture 2 shows an NP233 exploded view

 

I am going through a Electronic issue with my Jimmy, I can shift into 4lo but no access to 4hi..I just had the 4l60E transmission rebuilt, Now going to address Electronic 4x4 engagement...

I found a shop that spealize's in troubleshooting these Electronic 4x4 shifting mechanisms.. I have found most tranny shops dont have the patients or equipment to troubleshoot electronic 4x4 shifting...

You gotta have the right tools to diagnosis these electronic shifts or one is just throwing parts and money into the wind..

Could be a dash switch, bare wire, encoder mo on the transfer case.. this 4x4 axle engager on the front axle..Gotta be able to check for voltage levels within the module, and know what one is doing.... So I a, going to spend the $52 bucks and allow a professional fix my issue....Guy said it can take up to 3 hours to isolate these frickin electronic shifts, Also if you can get the transfer case to shift into 4lo then that will rule out the transfercase, and front axle engager..

 

Thanks, so many of these high mileage vehicles have problems with their 4wd. I have tested my encoder motor and TCCM in another blazer and it all worked to shift into 4wd but mine still nothing. It doesn't even turn the encoder motor when plugged into mine so i will keep checking around.

 

I know this is an old post but my 98 Blazer is doing the same thing....I got 4lo but no 4 high.

 

Did you ever find the snap ring for the transfer case spline? I am searching too.

 

I was never able to find one through GM or an auto parts stir they always told me "there is no spline on the front axel" which was obviously not the case. However I go to a local salvage yard every few months (and they are filled with Blazers and Jimmys) and I was able to pull the snap ring off and it now works like it's supposed to again!

 

Had the same problem. Check the vacuum lines. They tend to rot after awhile.

 

Bought 2000 trailblazer, Nice. Loaded with goodies including climate control. Backing into garage "Check four wheel drive" light came on. Went to forum which was helpful by saying code should be retrieved and read. Went to dealer stealer who said probably something simple that would maybe covered by the diagnostic fee. ($80.00) Not so. Service adviser called the next day and said I would need a transfer case control module at a cost of $379 and $200 labor. I declined. At first I thought the labor charge was a little excessive but later I found their labor charge to be numbing. I bought a refurbished module at Advance Auto for $249.00 and it literally took me fifteen minutes to swap them out in the parking lot. I have never done it before so I guessing it would take an experienced tech five to ten minutes to do this. Works fine now. It was stuck in four wheel drive before. I thank Haggerty GMC in Oak Lawn IL. for their diagnosis.

 

My 200 Blazer is having 4wd engagement problems. I found a torn membrane on the vacuum actuator under the battery. I replaced it, along with the vacuum valve on the top of the transfer case. It still will not engage. When the buttons are pressed to shift into 4wd, there is a light clicking sound that seems to come from under the dash, near the switch. It had been working, reluctantly, until just prior to the recent heavy snows, but when I needed it, it would not work. Any help will be appreciated. Thank you.