4WD does not engage properly 1999 Blazer

I would like to use 4WD for the icy roads we have now and when I use the push button for 4-HI the light switches from 2WD to 4-HI but the front wheels seem not to be engaged. The rear wheels spin with the front not turning. Is this a transfer case problem and is this a costly repair?

I would like to use 4WD for the icy roads we have now and when I use the push button for 4-HI the light switches from 2WD to 4-HI but the front wheels seem not to be engaged. The rear wheels spin with the front not turning. Is this a transfer case problem and is this a costly repair?



Check the FAQ section.


Sounds like a vacuum problem to the front axle.

Pefect! I will check the FAQ section. Thanks

Pefect! I will check the FAQ section. Thanks

Sorry, I meant the "How To " section

http://www.automotiveforums.com/vbulletin/showthread.php?t=620747




and here is the threads:

http://www.automotiveforums.com/vbulletin/showthread.php?t=498812

http://www.automotiveforums.com/vbulletin/showthread.php?t=572914

Thanks for the links laxman! I had a read and looked at the pics very good info. I have a 99 also and I was wondering where on the firewall I could locate the vacuum switch you had a problem with. It is so bloody cold here and get dark so early right now and I would like to now if its easily accessible or the is a little digging to do. If is not easily accessible I might have to wait for a few day to warm up. Thanks for the post it was very helpful.

Also to mention my lights for 2WD and 4-HI do switch back and forth and I hear a little clunk but when I am on slippery surface only the rear wheels turn. My question is this the same symptoms your Blazer had?

Thanks for the links laxman! I had a read and looked at the pics very good info. I have a 99 also and I was wondering where on the firewall I could locate the vacuum switch you had a problem with. It is so bloody cold here and get dark so early right now and I would like to now if its easily accessible or the is a little digging to do. If is not easily accessible I might have to wait for a few day to warm up. Thanks for the post it was very helpful.

Also to mention my lights for 2WD and 4-HI do switch back and forth and I hear a little clunk but when I am on slippery surface only the rear wheels turn. My question is this the same symptoms your Blazer had?



It's right above the distributor, it has two hoses running into it and a 2 wire plug, ya can't miss it.

http://img.photobucket.com/albums/v448/therealsundance/DSCF0085-1.jpg

http://img.photobucket.com/albums/v448/therealsundance/DSCF0087-1.jpg

http://img.photobucket.com/albums/v448/therealsundance/DSCF0088.jpg



Sorry about the blurry pics, it is dark out and there was no light so I was just using the flash. HAHA!

The switch has the blue on it.

That’s easy access alright. Thanks for the pics as that makes it very easy to see the part on the vehicle. I will check it out and hope it is malfunctioning and that’s my fix.

If that is working (you have vacuum on the upper port when in 4WD) then you might want to remove the battery and tray to look at the vacuum actuator (servo):

http://72.19.213.157/files/4WDDifferentialLockVacuumActuator.jpg