I've been searching and reading about the 4x4 system, but can't find an explanation for what I'm confuzzled about.

The 4x4 in my truck does not work, and I'm diagnosing it. The switch works, and I can hear the clicks coming from the TCCM. When I select 4hi, I hear the click, and the light stays lit. When I select 4low, it flashes a couple times, I hear the TCCM click, then hear the transfer case engaging.

I do not hear anything from the transfer case when going from 2hi to 4hi or vice versa. Is this normal? Does the TCCM only engage the front axle when 4hi is selected, and basically the TC is always in 4hi?

The bulb is out on the 2hi marker if that makes any difference...

 

no its not always engaged and you need to be in neutral to engage 4 low. Put it in 4 hi and get underneath and see if you can turn the front driveshaft. If not , thats good. Problem then may be a vacuum line or actuator

 

Sounds like the front diff is not locking-in. First check all the vacuum lines/hoses under the hood. I think '97 has the three button 4wd switch and the vacuum swith on the T-case that switches vacuum to the front diff actuator.

Also suggest checking to see that the T-case vacuum has the three vacuum lines connected and there is no fluid in them.

 

Was reading another thread about fluid in the lines... If there is fluid there, what would be allowing that? I'm going to be replacing my vacuum lines so just curious in case I see this.

 

fluid in lines is caused by a bad t case input seal let trans fluid leak in to the tcase filling it up. Also the 3 way vacuum switch on top of the t case is bad letting fluid up into the lines

 

So I decided to do some sleuthing today. Only because I got a nice heater in the garage now

So, the transfer case engages perfectly. Prop shaft is free in 2hi, engaged in 4hi and 4low. Seeing that this works I moved to the front to check if the front diff is locked. I start looking for the CV shafts to turn them by hand, and I'm having an unusually hard time finding them...

I then look at the wheel from under the truck and see an empty cv cup... FML...

So the poophead of a mechanic that did work on this truck when it was stuck in 4x4 decided to pull the shafts, destroy them, and put the cup ends in the diff and the wheels.

I didn't get to check if the actuator was there and hooked up, I was just too damn mad to carry on... The worst part is that the old man I bought it from showed me a receipt that he paid $600 to remove the 4x4 system, when it was probably the actuator that was stuck. $60 part and labour to fix that. I called him and told him to get a new mechanic, that douche is taking a poor old pensioner for a ride...

Now I'm just going to order the cv shafts, and get a posi lock system for the front diff and be done with it. Problem is, we're expecting that storm from the east cost to hit here in a couple days, and I have one helluva steep hill to climb lol Tractor trailers get stuck on it all the time when there's alot of snow... should be fun

 

Good call on the posi lock setup. Just did mine after screwing the vacuum system for 2 years. Works perfect did it this way. there`s even a link to the t handle. Quality part https://blazerforum.com/forum/builds...r-build-66048/

 

Since I am doing a posi lock system in it, is it safe to remove the vacuum lines going to the transfer case switch? Or are they needed for 4x4 engagement at the transfer case? I want to eliminate any extra lines I don't need... We all know that vacuum line leaks are a pain to find/diagnose...

 

yes it is, just did my T handle locking setup. works great. You can get vacuum caps at any parts store. The only one you want to leave is the vent line that comes up near your oil dipstick. Setup works great! wish I did it sooner

 

Got a silly question...when you guys say try to turn the shaft by hand are you referring to the shaft to each front wheel?


Got stuck in mud last night..4HI, AUTO, or 4LO would not engage. Lights just kept flashing. Cleaned TCCM connectors and applied di-electric grease. Can hear the TCCM click and something going on sounds like its moving from the transfer case.
This is frustrating as hell...