Hey guys...new to the forum. I have a problem with my auto-locking hubs on my 01 super duty. When I put it in 4 wheel from the cab I hear the front diff engage but no 4 wheel drive. I also have put it in manually, and still no 4 wheel drive. I understand it is engaged by a vacuum system. What should I check first? TIA Do I need new hub locks and where do I get them? thanks

 

I found on mine the vac. line from the chassy to the wheel was broken. Cost me $4.21 for a box of 5/16" vac. hose from Discount Auto Parts to fix the problem. Pull the front wheel and just check the vac. hoses. This is a high wear part. If not this then we can look further. Side note,, Diesel or gas?

 

are you sure the tranfer case is engaging? if you lock the hubs manually and the transfer case is engage you should have 4wheel drive. is the front drive shaft moving at all when you engage the transfer case from inside the cab. the transfer case is actually engaged with a small electric motor, only the auto-locking hubs are vacum actuated.

 

I agree but I thought it would be quick to check the vac hoses first. If the electric motor on the t/case isn't activating there will be no FWD. Jim

 

There is a big clunk when I put it in 4wd from the cab, so Im assuming its engaging but Im going to pull it apart tommorrow so please stay tuned.

 

You might just jack the front, engage the 4wd and see if it locks up. Let us know what you find. Jim

 

ok jacked up the front put it in 4wd and heard the "clunk". Then I spun the front wheel..........no 4wd. So I manually locked in the hub and same result. The truck is in park, in 4wd the front wheel should not spin correct? I did notice one of the vacuum lines had split at the end, so I cut a bit off and reattached it .........no difference. THe front drive shaft IS locking in ........in 4wd. I checked that with my hand.

 

ok ......this just got a little worse I think. I spun the front drive shaft with my hand as the truck sits in 2wd in park. I noticed the axle on the passenger side is spinning and the drivers side is jammed up.

 

It's not jammed up, your hub is locked in. rotate **** on hub and rock dive shaft back and forth and see if hub will unlock. sounds like your transfer case is working ok, you might pull hubs and do A clean and grease.

 

When you say no 4wd after the clunk what did you see.? Did you turn both wheels and nothing happen? Did one wheel turn and the front drive shaft but not the other. The fact that one locks up isn't necessarily bad unless we understand the total picture. I had the same issue and put the hub in auto/manual then tapped on it with a small hammer. The lock had stuck in engaged position. I plan to take mine apart and clean it. When you placed the hubs in manual engage they both should have engaged. If you turned 1 wheel and the other turned then you were engaged. If so I would have expected that the front drive shaft would turn,, if it did and your elec. system was in 4x4 then your transfer case is not locking and the selector motor on it might be bad. Not a big deal and relatively easy fix. Also when you selected 4x4 did you check to see if the vacuum pump was running. One easy way to check for vac leaks is to turn a/c on normal then select 4x4 HI. If you have a leak your a/c will most probably dump to defogger and no dash vent air.

So lets take this slowly. Jacked up both wheels in the air Hubs Auto. Engage 4x4 HI. switch key on. Does the vac pump run. Yes No. If yes does a/c stay in dash vents or fogger. Then check to see if wheels are locked. Which one or both. Then does drive shaft turn when you turn wheel. Truck in Park of course. Hope this helps. I just went through all this same stuff with my Ex 7.3 last week and mine is fully functional given the right hub sticks and will be pulled and serviced. Jim

 

I appreciate all the help.. In the process of jacking up each of the front wheels and locking and unlocking the hubs something changed(I think one must have been stuck) It went from the passenger wheel doing whatever the front drive shaft was doing and the drivers side just sitting there to .......both wheels doing whatever the front drive shaft is doing. I am mechanically inclined but know nothing about 4wd. SHould both wheels be locked in to the front drive shaft all the time and its locked in at the transfer case??? IF yes then I think It was just stuck and needs grease., IF no, THen I need to follow your troubleshooting idea in your last post

 

right now the on the fly 4wd is working and it locks in ..........its all good but the front drive shaft is spinning all the time(even in 2wd).......is this correct?

 

I think it is still a vacuum problem, you not only need vacuum to lock, you need it to unlock.

 

I went through this for YEARS........The auto locking front hub vacuum design Is junk.....The vacuum simply Isnt strong enough to activate the hub if Its dirty or worn......after years of frustration and several pairs of expensive auto hubs I took five minutes and replaced my hubs with warn manuel hubs......yes I have to actually take 30 seconds to get out of my truck to click the hubs In ..but when there IN thereIN and when there OUT there OUT.....AHHHHHHHHH BLISS

 

ALL hubs need to be maintained, if you don't clean and grease stock,warn, any hubs it will fail. I maintain my auto hubs and they work great. The stock hubs are not junk, it just take A little more ability to operate than A butter knife.