2002 4wd not engaging
 

Did many tests on my 4wd system from vacuum actuator to jacking up right front wheel and testing collar engagement, also 4wd works while sitting on jackstands but not on ground. Seems as if collar is engaging, i checked the tccm for corrosion, found some and cleaned good, and the transfer case is clicking for engagement very well. It seems the tc does not have enough pressure to engage the front axle while in 4wd. Leaning towards maybe the clutchs in the tc are worn and slipping? Can anyone help with this, very appreciated!! more snow in 24 hours and stuck in driveway, thanx

im having a similar problem.... started today

if i unhook the cable on my front differential and put it in 4wd the cable pulls like its supposed to... the differential will also engage by hand...... but once its all back together it will nto engage.... I dont know if the vaccum switch on the Tcase is not letting it have enough vac...... or the cable is stretched or the vac. actuator under the battery has a leak (or a vac line leak somewhere) its frustrating......... any help will be greatly appreciated

bad enough i just replaced the 4wd actuator on my full size chevy this week:icon_doh:

well
 

Well just changed a fuel pump in a voyager thats prob worth two hundred scrap, and the pump cost two hundred, i dont get it lol. Anyhow, i studied a lot on the blazer, went out and pulled the battery, found two lugs to jumper cable the truck and started it engaged the 4 hi and 4 lo and the actuator worked great. Could actually watch it function and move the cable, also the rubber diagphram was not brittle at all so all checked out. Its an easy and i feel, important test. Sounds like you really should check this first to see if it leads back to the tc. Im actually down to replacing the tc due to that fact it works in the air, everything does and when weight is on the vehicle it just wont pull. Everything is engaging and working properly ,, just think the clutchs in tc are gone, sis ran it in 4 lo over 40 mph for maybe twenty miles. Smells burnt?? any advice?

thanks all :icon_doh:

last i checked there were no clutched in the Tcase

my cable is being pulled by the actuator as well...... im just wondering if for some reason it doesnt have enough vaccum to fully engage the front end or if the cable is stretched

3-button switch or 4-button switch?

A test i learned for the front actuator to actually be confirmed as engaging is to jack up the right front, as it is the axle that needs to engage, and have an assistant engage four wheel drive in neutral. Before engaging the wheel will spin, after engaging the wheel will not. Seemed to rule that problem out for me, everything else on my blazer is checking out, buttons dont flash, tccm is clicking, front axle is engaging, it works on four jack stands fine, it just wont go when weight of vehicle is on it.
This one is a 4 button setup, i actually have one out of a envoy for 350 dollars at a junk yard, and almost ready to buy it, just wish i could be 100 percent sure its the problem. Im probably at 92 percent now. any advice would be appreciated.
Also will a envoy tc work for my blazer? thanks

ok, i have it in the air, did some final checks. Everything in the air works great, front wheels are spinning like they should every checks out, but the oil in tc smells burnt burnt burnt. so guess im changing it out, just concerned one person said there shouldnt be clutchs inside, wonder if just changing fluid would help hmm?

For the 4-button setup, you MUST use GM Autotrak II fluid in your transfer case. I would do that ASAP if it smells burnt. Hopefully someone didn't put the wrong stuff in, possibly ruining the clutch pack in the transfer case. And yes, there is a clutch pack in the transfer case.

Hey appreciate that, was hoping there was clutchs that would make sense why burnt up. Is that autotrak expensive at the dealer? can only get it there right? I actually found one for 350 dollars im looking at getting it tommorrow to swap out. Guess i have no other choice here? Would putting good fluid in help it come back? Noone shouldve filled it ever, never had it worked on like that so i just think sis burned it up, she did drive fast over 40 in low, so sounds like its probably cooked.
what you guys think?

It is more expensive than regular ATF, but it is a necessity. It isn't bad though. And yes, dealer only.

Driving fast in 4LO won't hurt the transfer case. The clutch is on the output side of the range box so driving 40 is driving 40 regardless of 4HI or 4LO.

Did you pull the fill plug? Was it up to the proper level?