4 wheel drive not engaging

[j.apps]

I have a 99 ford ranger and am having problems with my 4 wheel drive. I can turn the switch and the light on the dash turns on followed by a weird noise in the front differential. After this happens the truck still remains in 2 wheel drive. Anyone have any idea that the problem could be?

 

[Jspafford]

I would be willing to guess your PVH hubs are not locking. Check out the tech library for a write up on how to repair or replace them.

 

[metalmacguyver]

Before you go replacing parts, do a mechanical diagnosis.

Put it in 4hi, jack up the front end and put it on jack stands. Try to turn each tire by hand. You should not be able to with out the other tire rotating in the opposite direction. It makes funny noises, figure out where they are coming from.

 

[j.apps]

i did this and they lock while its jacked up, but then when i take it down it wont lock in

 

[rangerT]

i had the same problem when i bought my truck(i didn't have any history on it so you start from scratch).I did all the tests and thought it was the vacuum module as there wasn't much vac downstream of it....(wrong), worked once then that was it back to square one.i wanted to keep my auto's but for the time to try and figure where and what needs replacing i went with a set of AVM(rugged trail)for 200 shipped. works like a charm and now i know it is locked in........one other test you can do is pop off the auto hubs and lock/engage them and then pop them back on and you should be locked in.....or on the down stream side of the vacuum res.(just underneath the plastic inner fender on the passenger side)connect it straight to the feed lines going to the hubs(eliminating the module and gives it the full vacuum with no restrictions)....GL hope this helps