1998 ZR2 auto.

i can push the 4hi button and hear a click behind the dash somewhere but that is all that happens. the light does not flash, nothing. fuses are good.

bad button, module, encoder? same symptoms with 4lo as well.

 

put the truck into neutral then try it that way

 

tried it in Neutral. when the 4wd button is pushed, both 4hi and 4lo lights flash then it goes back to 2wd. the more times you push it, the fewer times they will flash till it does not flash at all.

anyway to bypass it and manually put it into 4wd? i know the T-case it is as simple as pulling the shift motor and putting the transfer case into the desired gear, but what about the front actuator?

 

TCCM possibly?

 

Checked and no corrosion was found. not saying it is not the issue, but it is not the common corrosion issue with them. i still hear the relay click.

got under it, and sounds like it may be in the T-case itself. in 2wd, i can't spin the front D-shaft. have not tried jacking the front end up, but without the axle engaged i should be able to spin it i thought. when the rear d-shaft is spun sounds like a light grinding noise from inside the case.

may end up pulling it and tearing it apart.

 

check vac lines?

 

Sounds like you have the 3-button switch (NV233) from your description (no mention of Auto4wd) so when in 2HI you should be able to turn the front driveshaft. But if the front axle is not properly disengaging, then you wouldn't be able to turn the front driveshaft without at least one front wheel off the ground.

If your lights aren't even blinking, you have a problem in the control circuitry which includes the switch, the TCCM, and the encoder motor. The switch is easy enough to check. The NV233 switch is simple contacts that close when a button is pushed.

Have you checked for codes? 96+ NV233 Diagnosis

 

i'll try to check for codes tomorrow. i thought the days of checking codes with jumper wires ended with OBD I vehicles lol. guess not.

 

long story short i just went through the same prob. The clicking is the relays in you tccm. It is is the dash kinda behind the ashtray. Silver in color big blue plug. One of the relays are not working in it. Unfortunatly theyy are hard wired into the board so replace the tccm. Don't pay more than 40 buck for a used one. If you can't find one for that amount let me know i can find one. Many junkyards sell out of tccm's becouse this is such a common prob with the 2nd gen blazer and jimmy