front diff will not engage

ok guys here we go search a lot of post but i'm still puzl

I have a 1991 blazer 4.3 manual 4x4 on the flour, when i put it into 4wd low or hi the front diff is not working the light lights up on the 4wdL or 4wdH ( the little round light) BUT the pic of the truck with the wheels only has the back wheel lit which seems to stay that way.

Would low of bad fluid in the Diff cause this prob?

The things i have cheaked 1) shift linkage to the trans case GOOD
2)all 3 of the vac lines from the trans case one to the intake, one to the air can(round ball), and one the actuator (which douse suck in when it is switch into 4wd) Seams to bo all good

There was also a T fitten off one of the lines which branched into the trans case this hose was kinked so i fixed it, WHAT is that for?

What do i do next, it there a fuse? should i pull the cable out of the front diff and inspect? Is the front Diff bad? any sug would help thanks.

ttt.. i hope there is some one that can help
should i have subjected this different? i tried to search for this post and i couldent even find it.

i have been looking at other post and found that maby the vac switch on the trans case could be bad, iS THIS true even if though my acuator (cruse control looking thing) is still gettin sucked in?

ALSO can i push it the cable under my Batt in by hand and vise gripe it in that way to cheak? this should ingage 4x4 right?
Thanks GTAfanatic

No, you posted everything properly, just a slow night I guess. I don't know when you posted the topic, but you'll usually have the answer within 24 hours, or never.

Welcome to Automotive Forums! :cheers:

This link should help you solve your problem.
http://www.4x4posi-lok.com/PDFs/TSG_chevyT.pdf
It's the best trouble shooting guide that I've seen on the subject.

thanks for the welcome, i posted two days ago. i did cheak out that site, did not help. i noticed it when i was looking around.

Try putting it into 4wd, with the motor shut off but it in gear or park.
Crawl underneath and try spinning the front drive shaft. If it spins then the problem is your transfer case.

Next pop the hood, and jack up a front tire, and get a friend to spin it (with it still in gear and the transfer case in 4wd) Pull on the cable running to the front diff (at the vacuum pot) It should stop the front tire.

If it doesn't it's either that cable, or in the T-case it's self. Hopefully the cable.

Let me know what the results are.

I wouldn't worry about only the back wheels lights lighting up. That could be a bad bulb, or switch and really doesn't mean much with the manual shifter.

Fix IT NICE :biggrin:
Time to close this post i hope this can help someone else.

The problem was in the cable where it goes into the front Diff there is this spring looded clip that connects the shaft (in the side of the diff) to the cable, the spring was out of place. i clicked it back into place and BAM good to go.
Thanks for the help it was a good way to test the transf case and ect...

No prob.

I don't think that you can use this technique with a push button, but I don't know.

Glad that it worked out for you

check the diaphram for the 4 wheel drive i had a 88 jimmy and i had to use vise grips for the 4 wheel to engage

It's already fixxed a7x278, but thanks for the reply.