1994 F-150 4WD with 5.8 L. EO4D auto & Warner 1356 transfer case.

I've been getting an awful shake in the driver's side tire at speeds above 40 MPH. The roads here are crowned and pitched to drain. The turns are fairly tight for a high speed road.

Where i'm getting the problem is on a right hand turn when the weight of the truck shifts over to the driver's side. At about 37 MPH there's a sound like a roller bearing spinning up and then at 40 MPH a violent shake in tire / wheel assy.

I've rebuilt the front brake system to resolve some problems there.

Been through the front end. The power steering box was bad so that was replaced w/ a rebuild. Tie rod ends & ball joints are in good shape. Front end alignment is about as close as you can get it using the string method. (There's a wee bit of toe in.)

All four shocks are new and seem to be working right.

At this point i'm thinking it must be in the automatic locking hub. For whatever reason it's engaging the half shaft at random intervals without the transfer case being engaged.

To prove it i benchmarked the shaft with a paint marker. After one of the shake episodes the shaft had turned.

Otherwise ... if there's no shake the shaft stays in place.

I pulled the left automatic locking hub yesterday and all of the splines on the hub and the wheel look to be in good shape. Two of the four ears on the back of the hub assy look to have taken a little bit of damage.

Just to be on the safe side i've pulled the drive shaft going from the transfer case to the front differential. That way if there's something ugly going on the shock isn't being transmitted back into the drive system.

With the drive shaft out the truck drives a lot smoother.

Both hubs are going to be changed out to manual locking hubs just on principle.

I'm wondering if i should be checking for and damage or problems with either the front differential or transfer case as well ?

Where i work outdoors my aim is to get the truck in good shape before the winter sets it. Having to work under the truck in the middle of January when it's bitter cold isn't much fun. It's an ounce of prevention thing ...

Any thoughts or insight would be appreciated.

 

Have you replaced the wheel bearings? My truck would make a humming noise around faster corners and at higher speeds. I replaced them with new races and seals and has been great ever since.

 

That's a good point. I've checked the front repeatedly for any kind of play but it could be a bearing in there that needs to be replace.

There's one corner where it will shake every time if i'm going at speed. Hit that yesterday after i had pulled the front drive shaft and it still shook ... just not as bad.

I'm gonna pull everything apart when i go to do the manual front locking hubs.

Just wondering if it could be the half shaft to that side sliding back and forth even though there's no power being transmitted to it from the transfer case.

 

What your describing sounds exactly like an auto hub not properly disengaged. One side would lock and the other side would spin freely. As long as you didn't drive long distances with one hub stuck, the front diff should be fine.
Without the front shaft in place it won't want to fight against the t-case so that would explain how its smoother, even if its not engaged. If you have the 3 bolt auto hubs remember you need the conversion kit to use the 5 bolt manual hubs.

Do you have a manual or electronic case? Be sure is properly engaging into 2wd and 4wd

 

Fortunately, i've got the five bolt automatic hubs. That should make the conversion over to manual hubs fairly simple. The only question in my mind about it is that i might need a different spindle nut for the conversion ?

I've got the manual case. It shifts effortlessly from 2 H. to 4H.

It doesn't like going down into neutral to accomplish the shift to 4L. What i did was gently tap the top of the shifter with a 3 lb sledge and it went down in. It shifted back out of 2L up into high range without very much trouble.

I tested the 4 WD to make sure it's working ... on dry pavement.

There's no doubt that there's a difference between 2H & 4H.

Where the truck is an unknown there's always the possibility that the shifter could be a bit out of adjustment.

What i thought i would do after converting over to manual hubs is to benchmark both of the half shafts and the front drive shaft. Run it in 2H for a little while and then check it.

As nearly as i can guess there shouldn't be any movement with the manual hubs locked out and the transfer case in 2H ?

 

sounds to me like you have a vacume leak the front hubs default to lock position when there is no vacume and if there is little to no vacume or just low vacume they will try to lock and cause the problem you describe.might bear looking into.

 

If circumstances were a little different that might be the case.

With the "94" there's no vacuum system to activate the front differential.

My best understanding so far is that it's the torque coming down from the transfer case that causes the front locking hubs to engage. The step by step process of how it actually works is a mystery to me at this point though.

Near as i can figure it will probably somewhere between 80.00 - 130.00 $ for the locking hubs by the time it was all said and done. My carpentry business was pretty slow in August so there hasn't been much coming in. It will be a couple of weeks before i have the extra to put into the hubs. In the meantime ... i'll just baby it along. Most of my driving is under 40 MPH & i seldom travel more than 8 miles from the shop.

I thought what i'd do is change out the hubs and then see where i am. It might be the kind of thing that once it's done it's problem solved.

On the other hand ... there might be more to the story.

Once everything is de-rusted and coated in never seize it's only ten minutes work to reinstall the front drive shaft.

It might work better to run it as a 2 WD truck most of the year and leave the 4WD option for when i really need it during the winter months.

The steering isn't quite right yet. It's a funny thing ... every time the truck gets anywhere near a gas station there's this wicked pull to the right.