2000 ZR2 blazer. Service 4wd trouble light illuminated on dash since purchased. Replaced 4 button switch on dash, sorted out all grounds. Lights on 4 button used to flash a little, don't even do that any more. 20A ATC fuse in underhood fuse block ok. 10A 4WD fuse in driver door jamb box ok. Nothing happens when buttons are pushed. Encoder motor now removed. No 12v power at tan wire on the 4 pin block that goes to the encoder motor. My diagnostics guy says that means a new encoder motor won't help. Somebody ran a 16ga black bypass wire all the way from the computer box on the passenger kick panel into the loom on the left side of the transmission. My faith in the OEM wiring isn't high at this point.

I'm ready to ditch all electronic devices controlling the 4wd and put a floor shifter in for the transfer case and a pull cable for the front axle lock. I've read it's "not recommended" to do this with the Auto 4wd drive transfer case and that I need to switch to a different transfer case. Why would this be necessary? This is an $800 ZR2 that I want the 4x4 to function for EMS calls. If it eventually causes the failure of the t-case, I really don't care. If it means the truck won't drive right, then that's what I need to know, and will pursue other means.

Thanks in advance

 

Sorry, I'm no help.

 

The answer as to why it isn't recommended to do this with the NV236/NV246 transfer cases is due to the fact that there are no detents for 4HI in the transfer case controls. The encoder motor has a built in brake that holds the position of the motor and shift sector shaft for a given mode. When in Auto4WD, the encoder motor will rotate the shift sector shaft and apply pressure to the front output viscous coupling in response to detected slip. This varies the amount of torque transferred to the front axle. The encoder will move and the motor brake will apply to hold that setting until the TCCM tells it to move again. Without detents, there would be nothing to hold your shift lever in position aside from you designing & fabricating a shifter assembly to do so which wouldn't be all that difficult, but does add another layer of complexity to the conversion that folks with the 3-button NV233/243 trucks do not have to deal with.

 

Kinda off topic, but since it's kinda brought up...

I've always wondered how the 236 cases work. I've been through my 233 case, and rebuilt it. It's a really simple unit. Does the 236 have a chain? Or is it only a viscous coupling like you mentioned?

 

Most transfer cases have chains. In the case of the NP236 transfer case, it has a 1" wide 49 link chain (if my source is correct). The main difference between the NP233C & the NP236 is that the upper sprocket is attached to the viscous coupling (wet clutch) that is responsible for driving the front output.

Fun thing I just found out, they now sell frictions & steels to rebuild the viscous coupling in these transfer cases. In the past, they weren't available.

 

Oh, OK. Makes sense. Thanks for the explanation