Hey,

I had a mechanic tell me the transfer case on my 99 blazer was seized up.

NP236 with 4 button 4WD

I wanted to verify for myself so I marked the starting location of the shaft (for lack of a proper term). Was able to move it somewhat easily using two hands on the 17mm wrench.

My question is: how many positions should I be able to get on the wrench? 2 hi, N, 4 hi, 4 lo?

How do I know which position relates to which mode? I can’t find this info anywhere.

How hard should it be to change positions with the wrench?

Thanks in advanced!

Brandon

 

Hi,

I looked in my GM 99 service manual and the best I could find were the pages I've scanned and posted below. I couldn't find anything the discussed which position corresponded to which drive mode. All the other diagnostic info relied on an OBD code reader.

Maybe a transmission repair shop or online video can help? Is the encoder/motor functional? If so, perhaps you could remove it but leave it connected electrically so that you could activate each mode and then note which position corresponded to each mode?

 

Thanks for the reply. I’m new here and not sure how to directly reply to your comment.

anyways, the encoder motor ohms out ok but I think it’s off in position a few teeth. If I install it on the shaft, it is about a half a hole off for the bolt holes.

There is a label on the encoder that says operating the encoding without the load of the transfer case will cause damage.

Thanks for taking the time to scan those pages in.

 

Sorry I could not help more.

Good luck and keep us posted!

 

Thanks.

Any idea where to find a pdf of GMPT/99-TURM?

Apparently this the manual for the transmission and transfer case

 

In case anyone finds this in the future…

I figured out there are 3 positions.
2H/4H, Neutral, and 4L

Neutral is straight up and down. 4L is full CCW and 2H/4H is full clockwise.

The difference between 4H and 2H is that in 4H the front differential is locked in.

 

Nice job and thanks for posting what you learned.

Where did you find the info?

 

Hours of looking up anything I could find about how the NV236 or NV246 works since it seems to be very similar to the 236.

Then I confirmed when I had the Blazer on jack stands.

I found a good article, but I’m not a mechanic so alot of it went over my head.

https://www.transmissiondigest.com/a...transfer-case/

and then this one:

https://www.transmissiondigest.com/n...ng-the-tricks/

Again, I’m not an expert or even close. But my understanding is that the 246 is a beefier version of the 236. How it operates is basically the same. And there is very limited info on the operation of the 236 that I was able to find online and YouTube.

Hope this helps someone.

 

There are more than 3 shaft positions on a 4-button transfer case. See attachment.

Also the same is found here https://blazerforum.com/forum/2nd-ge...-blazer-89044/

 

Regarding the transfer case selector shaft that the encoder motor actuates, I thought there was only 3 positions.

But it sounds like it also applies a known torque to the selector that will engage a clutch pack for 4 Auto?

But if I were to put a wrench on the shaft, I should only find 3 positions (hopefully)?

Thanks for the info!!