Ok guys first of all good info on your forum here. I'm attempting to fix my inlaws blazer, first observation I made was the vacuum actuator was not pulling the cable when the 4 hi button was pressed, so I replaced the vacuum switch today and now the vac actuator pulls the cable but still no 4 wd. The cable looks good. From the first link in post #5 in this thread it says there is internal damage to the front diff due to incomplete actuation. Does this sound right? Any info on how to proceed would be great.

The lights for the 3 buttons still work as if everything is ok.

Edit: I suppose I should have pulled the cable out where it connects to the front diff and watched for proper action there? I'm really hoping it's not the diff, but if it is I want to make sure it is before I attempt that.

 

Mb,
I have the same exact problem so I am interested in someone responding.
I too was not getting the vacuum actuator to pull in either. I replace the vacuum switch on the transfer case and this fixed the problem,,,so I thought. I removed the cable off the the front differential ,as Hayes manual said, and disconnected the cable. Hit the 4 HI button and the cable pulled and was working. It seems whatever is in the front differential is not shifting. I looked for diagrams, but could not find an accurate one of my 98 blazer.
Has anyone ever had this same issue? Is there a rebuild kit for this?
One, thing,, I did have the garage replace the CV shafts over the summer,,could they have damaged something by installing them with too much force?

 

Just in case anyone stumbles upon this thread and is in the same situation I was, here is an update (even though its very late). I finally broke in and bought a new transfer case shift motor for about $200. I replaced it with the used one I got from the junk yard and everything seems to be working great!

Doing the self diagnostics by grounding the pins was a great idea and I would recommend others to try that. I had a much better idea of what the problem was then the dealership did when they ran the diagnostics (pretty sad!).

BTW I was forced to drop the front drive shaft in order to replace the motor. I first attempted to remove it without dropping the shaft but the top of the shift motor gets caught.

 

Hi, i seem to have the same problem candersonosu had, not fixed yet. How long did it take for your TCCM to store a code 2 after you cleared it. I am trying to recreated the problem right after I clear the code 2 I get but cant recreate it. It seems like it takes to weeks and I dont use the 4hi within that time and when I do it doesn't work. I checked the voltage from the TCCM at the connector on the encoder motor and everything is fine, no shorts or opens.
I realy wish I could find pictures of the insides of an encoder motor.
Please reply
Thanks
Buddy

 

my 4wd didnt work wen i got my blazer guy i knew helped me out we had to tap into another vac line n it workd fine for almost a year. one week i went out wheelin workd fine next week i took sm buddies from work out n got stuck for hours at bout 1am luckily sm1 came at about 3 pulld me out 4wd never word since i checkd most of my vac lines replaced a few of them and replaced the vac switch . the 4hi lights up lo blinks wont stay on actuater pulls in and releases. cant tell if cable is broken in the actuater and cant figure out how to get it out of the diff. will a regular obd tell me if its my tccm or smthing else electronic? t
any tips wd be great sorry for long post its my 2nd 1 i signed up last night thanx ev1

 

Swartlkk that helped me alot thank u my truck hasn't had 4wd in 4yrs I just git good at 2wheel lol but love that I can just crawl up hills and on trails now rather then having to punch it over and thru everything but thanks tested the t-case at like 130 after I read that thread and couldn't wait to wake up and look more into it ... had 4wd in about an hour and installed the posi lock cable the homemade way in another 30mins figure worst case I carry spare parts to repair on the trail just didn't want to rely on vacuum ... is there a way to make the t-case not vacuum or is it not? ?

 

I have an 01 Blazer LT and i don't think my 4wd is engaging. its also an electronic push button 4wd. whenever i go into 4LO it says the light is supposed to stop blinking after 30seconds indicating that 4LO is engaged but the light never stops blinking. i have no idea what is wrong.

 

Check out the link in post #9 in this thread. This comes from the DIY section. There are step by step instructions for diagnosing 4WD problems for those with electronic shift transfer cases.