Ok I do love my truck but twice now its let me down. The lights on the dash work but only the rear wheels spin. Kinda scary was in the mountains yesterday on a very slick muddy road and the rear of the truck kept sliding towards the edge of the road. Then it happened with about a month ago when it snowed. It does sometimes work. I'm puzzled please help. Thanks, Dan

 

Help.... Please...

 

Hmm, more info please. 4 wheel hi, lo, or AWD?
Were you in low gear going down the hill?
Were you allowing the rig to idle down the hill or were you applying the brakes?

Bob K.

 

Any setting. I was going uphill. The rear end was sliding because I had no 4wd. It wasn't engaging. I do alot of wheeling I know what makes a truck go sideways downhill. lol Its just plain old broken... The truck has 105k on it is there anything that normally causes this problem. Thanks, Dan

 

Sorry, just went back and read my post. Didn't say whether I was going up or downhill. hehe

 

In a nice dry spot, crank the truck, put it in 4WD and climb under and see if the front driveshaft is now locked in. (It should be held stopped just like the rear one...in park).

If it isn't, the check the shifter motor for a loose wire or fuse out.

If it is, then it may be the hubs.

Chock the wheels, on both sides.

Shift from Park to Neutral. Try the front drive shaft again. Now the drive shaft should be locked from moving because the wheels can not move. If it spins free, then you've got a hub problem.





Bob K.

 

Well for starters.... These vehicles have no hubs on them! They are locked directly to the axle via splines in the wheel hub it self. It could be as stated above..... the shift motor. You should be able to hear this motor if you shut the truck off and turn the key to on. Then turn your selsctor on the dash. It should make a clunk when it turns. If you do not hear this clunk then it is the motor. If the motor does clunk then you got another problem. There is a vacuum pump on the front differential. There ars a few lines on it that go to the fire wall on the passenger side of the vehicle. Check these lines carefully... I have seen them come loose or simply crack and leak.... either way it won't work. I hope tis has helped a bit. This is not that complex of a system unless you get involved with the A4WD section of it.

 

The axle spline matchup at the end that the wheel rides on is still the 'hub'. You called it that yourself...;-)



Bob K.

 

Thanks guys, I now have somewhere to start. I will check all that was stated over the weekend. Maybe today if it stops raining. Thanks again, Dan

 

NWBronco...

I believe (although I'm not entirely positive) that what Freek meant is that our Expys don't have 'hubs' in the traditional sense of part time 4wd vehicles. There is no switching of power on and off at the hub...the hubs are solidly engaged to the axleshaft splines and the axleshafts always spin. Thus, looking at the 'hubs' would not be a worthwhile experience--there aren't any parts to go bad/seize up/etc. So while you meant selectable hubs (I think--based on what you said in your post), meaning devices incorporated into the hub that engage/disengage to either lock or unlock the rotation of the wheel to the rotation of the axleshaft, Freek meant hubs as in the component of the axle that is between the bearings and the wheel. To put it another way--the Expys act like they have drive flanges instead of hubs at the front wheels.

I believe--but again I'm not sure--that the vacuum lines going to the vicinity of the center differential operate some form of central axle disconnect on the front axle for 2wd operation.

So there should never be a problem with a hub on an Expy--they don't have any moving parts. If you've got a hub problem--well--then you've got serious problems! (I.e. wheels falling off, etc.).

I think the diagnostic tests suggested are pretty right-on, both the 'stop and listen' and the 'stop and turn'. Just replace the "you've got a hub problem" part of Bronc's post with "you've got a vacuum motor problem."

 

motor on the transger case maybe...that was my problem

 

Chixon, Unrelated to my post, I saw your sig. What type of 3" lift do you have? Someone told me I could stuff 285's under my stock Expy do you think its possible.

 

dk... as you stated above yes there is a hub, but it has no moving peices to fail. There is no means of disconnect in them. If they fail.... as Farmlaw states you will definately have major problems....ie: the front wheels will fall off! Or better yet, the bearings could seize up and throw you into a spin on the interstate and roll your Expy a half a dozen times.... then you wouldn't worry wether the 4x4 worked or not. The vacuum motor is an axle disconnect just like stated above. I have seen hoses come off or get hung on tree limbs off road and get ripped off. The only thing that protects these lines from obsticals is a flimsy plastic cover. If you crawl under the front end of your truck and look at the differential you will see a black cover. Behind this cover is the vaccuuum motor that is described.

 

Keep me out of the fight, DK didn't say anything about having hubs. lol hehe I understood what you guys meant. Thanks for the location for the vac. motor. You said I should hear a noise when I turn the selector switch. Not hearing anything. Will check the rest of the list. Thanks

 

Ok, I hear clicking from the dash.. Only clunk is when I put it in 4 low. Its wet out when I smash the pedal in 4hi only the rear wheels spin. And of coarse the truck wants to go sideways so that tells me 4wd in hi isn't working. Am I right? Front should spin with rear tires. Thats what happens in my F-250 when I am in 4wd hi.