4wd issues

Buellstunter · Dec 17, 2013

Been having trouble with getting my truck into 4wd. It still has factory hubs and truck has 215,xxx miles on it. I bought the truck in may. I tried the 4wd and it worked. tried it a few weeks ago in the snow and nothing then all the sudden I noticed it was working. so I tried using it the other day again and not working again. With hubs in auto I turn dash switch to 4hi light in dash comes on but doesn't engage in 4x4. So I manually lock my hubs switch to 4hi and the light in the dash comes on, but still no 4wd??? So I craw under the truck in 2wd and can spin front drive shaft by hand. turn switch to 4hi and front drive shaft locks in. so I assume the shift motor and the transfer case is working. so I check all the vacuum lines with my vacuum brake bleeder. hook it to the line from the vacuum solenoid on pass front fender that goes down to both hubs and it pumps up and will holds vacuum. so I'm assuming no leak. have someone flip the switch to 4hi and the vacuum solenoid pulses can hear the vacuum canister loosing air and the vacuum pump kicks on. seems like the system is working properly, so I'm guessing it is some issue with the hubs but not sure.:shrug: can Anyone give me some pointers on what to try/check next? thanks in advance!

SaNnDnSurF · Dec 17, 2013

I had an issue with mine one if the nipples at the hub was plugged up but mine would still engage manually so not sure if that's your issue here.

SaNnDnSurF · Dec 17, 2013

It only takes a few minutes to pull and check them though so might be worth a shot.

Buellstunter · Dec 17, 2013

Thanks. I'll give it a try!

Buellstunter · Dec 17, 2013

Noticed today that my heater does default to defrost when I put it in 4wd. But if I wait till the heater goes back to the floor. I have 4wd with the hubs locked in. Not in auto. So I guess I have some sort of vacuum leak as well. Still don't understand why with them manually locked it would be affected by vacuum? Unless the manual locking of the hubs don't work properly either.

SaNnDnSurF · Dec 17, 2013

You should be able to lock them in manually even with a vacuum leak sounds like a hub issue and possibly also vac leak

Trqmnstr · Dec 18, 2013

Yup
Hubs and vac leak. The dash light wont turn on unless the t case locks in so your motor is good like you said. The stock hubs get dirty and wont engage sometimes even with good vacuum. Ar the hubs hard to manually lock? They should be smooth and easy to lock. If not i would just get some new ones in there. Ive had hubs grow a mind of their own and one side would lock and unlock when it wanted to, you don't want that going on trust me. Lol

Buellstunter · Dec 18, 2013

Trqmnstr said:
Yup
Hubs and vac leak. The dash light wont turn on unless the t case locks in so your motor is good like you said. The stock hubs get dirty and wont engage sometimes even with good vacuum. Ar the hubs hard to manually lock? They should be smooth and easy to lock. If not i would just get some new ones in there. Ive had hubs grow a mind of their own and one side would lock and unlock when it wanted to, you don't want that going on trust me. Lol

Thanks for the reply. My hubs do turn smoothly by hand to manually lock them in. Almost feels like no resistance at all. And I'm assuming that they can be pulled apart and serviced/cleaned up and maybe fresh grease put in them and they will work again. Also will a vacuum leak cause them to not engage even if manually locked in, does the vacuum still play a part in the hub if they are in manual lock? sorry for all the questions, just trying to get a better understanding on how the system works. thanks.

Trqmnstr · Dec 19, 2013

Vacuum plays no part in the system if you manually lock the hubs. I cant remember how the hubs actually worked but iirc there is a spring in there that locks the hub when you manually lock them. Or at least it feels like it.
When i had mine off one side would spin free while locked but if i rotated the whole hub around or shook it it would lock and unlock even with the hub set on lock. Ended up rollin around unlocked in winter on bald tires till i got new hubs in the mail.

I have read that the dash light wont turn on unless the t case is engaged but i also remember having t case engaged and no dash light. If your t case starts not wanting to lock just tap on the motor with a hammer. It should engage then but youll want to get a new t case motor pronto.