I just picked up a '97 Jimmy for the winter, has the 3-button which I believe is the NV233. 4x4 isn't working..when i select neuttral and push one of the 4HI or 4LO, lights just flash and module in dash clicks on and of a few times in-sync with teh buttons flashing. I pullled codes and I got "1"..I checked all power and grounds to the TCCM, al are good.

I all powers to the encoder motor, all are good. I removed the encoder motor and let hang there while plugged in, motor moves 1/4inch and binds up internally. I opened up the encoder motor and found the motor gear rusted/siezed to the casing..beyond repair..

So I selected 4HI manually and did not press any button.. all 4 wheels are driven on a lift. I set back to 2WD and only rear spins as they should but I noticed the front diff is engaged and not open via the cable.. I set back to 4HI and tried to hold RH front wheel..cannot be stopped..be advised buttons have not been pressed

Took on the road, wet pavement..only rear wheels spin while T.C is manually selected on 4HI...I set to neutral and selected button 4HI...4HI and 4LO light up and stay lit..shift back to drive and still have no front wheel engagement on road..I have yet to put vehicle back on lift to see if the front still spins when manually selecting 4HI..

Is there a possible problem with the front diff engagement..do I need to do anything to engage the front if I manually select the 4HI postion by turing T.C selector shaft?

 

Does the tcase lock into the 4wd ranges? Its possible a bad vac switch.... But I would not guess.. Id start by diagnosing the system...


This should help 4x4 No Worky.... Maybe this will help.... - Blazer Forum - Chevy Blazer Forums

 

You don't have to do anything except ensure that vacuum is reaching the actuator under the battery tray, and the cable attached to the actuator is doing its job (i.e. pulling the shift collar that joins the two shafts). When shifting manually, the linkage inside the transfer case will still open the vacuum switch, but no vacuum = no front diff engagement.

 

Almost understand the complete system. The switch in the dash only sends a request to the TCCM, TCCM send back the confirmation via the L.E.D light lit ..when say 4HI is engaged via the switch and the system is operating as it should..I'm guessing only the 4HI button l.e.d be lid(with my encoder motor disconnected now 4HI and 4LO come on together) ..what about also when in 2WD, will the 2WD button be lit? ..just asking cause with mine in 2WD no light is lit..just wondering if this is normal..

I'm going to dig deeper into the front axle not engaging tonite, going to check the vacuum/actuator/switch/cable..only bought this for the winter, so I might keep the T.C in 4HI manually and do the cable mod for the front diff..that way I can have some-what of a 2WD without needing to switch the T.C for parking and highway driving ..I don't really want to do the manual T.C shifter mod I saw on here(cutting the floor..etc) ..I only paid 600$ for the truck and plan on selling it come winter end when snow is gone (end of March)..so to spend 150-200 on a encoder and possibly a actuator, versus a universal cable from NaPa to lock and release the front ..but I want to keep it looking somewhat original to sell it after..LoL guess it really comes down to how much I wanna spend on this

I know I'm new to this site, But on a side note, amazing how much info is on this blazerforum, with some very knowledgeable ppl!! Thanx for the response's guys! Keep you posted on what I find and decide..

 

Sounds like you have bad bulbs in the 4wd switch.... Id repair that so it wont drive ya nuts while diagnosing the system. ALSO if your manually shifting it the indicators wont work because the motor is not connected...

AS for your front diff. You can lock it manual in 2 ways

Posi lock system.
Homemade posi-lock cable system

Or you can go with an electrical locking system.
Front Differential Electric Locking System DIY

 

I did the homemade posi lock like the first one Gio posted the link to but I did my own version of it. I have a bunch of pics in my build thread let me know if you have any questions or would like more detail. I still think its one of the best mods I have done and it only cost about $40. The thing that I like about mine over the other one is that I didn't have to cut my bracket so if I decided to I could put it back to the stock setup in about 30 min or less

 

So I checked the truck over last nite after work. The front diff is locked engaged even in 2WD, I released the vacuum to the T.C switch and the front axle disengaged..so at least I know everything frontwards is ok...I removed the switch but don't know at what position its venting, when removed should it be venting or in pass-through? ..when I had it removed and in my hand all 3 ports are blocked

I've tried searching but can find anything, how do I know which vacuum lines are which on the grommet with out testing each with a pump..there's the 2 small and 1 large hose's on the grommet..

Being I paid $600 for the truck, and having a encoder fault and vacuum switch fault.. actually thinking on doing the cut the floor mod for the T.C and fitting a locking cable like you guys are giving links too for the front diff. I could keep it in 4HI and just use the locking cable to the front, but when selling I think I could possibly attrack more ppl(offroad area) with the being able to still select 2WD, 4HI and 4LO manually on demand..to stop water from entering the cabin I could just get a boot from the scrapper to go around the cut section in the floor and use a threaded rod bent to shape instead of wrenchs with a shinny **** on top ..hehe idea's are all up in the air though ..only real thing holding me back right now is no access to a MIG

 

IT can be done.... Ive done the manual shift on a 233c. Check out my build thread.. IT should be towards the end.

A bad vac switch can cause it to not disengage the front end.

 

Awesome, that's right on the lines of what I'm thinking..did you ever put the center console back in..if so did you have enough room..after doing this would you have done the handle different?

How did you secure the gear back to the T.C selector shaft, can't really see in the pic..doesn't look welded??

 

I added a small pin and yes my console is back in.

You need to remember tho my truck is a 1st generation. The location of the shifter might be different.