1994 F-250 4x4 Rear end up and down movement at 40+ MPH
 

Hi,

I have a 1994 F-250 4x4 460 SC AT 4.10 that has 150+000 miles on it that I've owned since 1997. The truck is as stock as the day that it came off the showroom floor.

The truck has never been in a wreck or hit curb, etc. and it is only driven when we pull our 24ft travel trailer or mount a 8ft Lance camper on the back.

Several years ago, I noticed that one rear tire was wearing on the outer edge, but only on 1/2 of the tire, not around the entire circumference. (Kind of like around the crust edge of a 1/2 slice of a whole pie, not the entire pie.) The tire store replaced the tire thinking it was a defect in the tire. At that time the truck had our 8ft camper mounted on it and was stored in that configuration when not used. Unfortunately I cannot remember which side the tire came from on the rear.

A couple of years ago, we took the camper off and used the truck to haul our travel trailer and I noticed an up and down movement in the truck when traveling at speeds over 40 MPH. The movement smooths out at around 50 and is barely noticeable beyond. This up and down movement was not felt with the camper on, only when it came off and there was no weight present in the rear bed. The movement is felt whether there is a trailer hitched or with no trailer. The movement is felt within the truck at the driver and passenger front seats. I have sat in the bed of the truck trying to determine exactly where the movement is coming from, but after several hours of doing so, I cannot pinpoint a specific location.

I have since replaced the shocks with Monroes, checked all front steering components and all is good, had the driveline checked for balance by Six States and rebalanced, and replaced the u-joints and the carrier bearing. No luck in eliminating the up and down movement...

I have replaced the tires with Michelen radials and the tire store did a road force balance on all tires and they checked the stock steel wheels prior to mounting the tires.

I have jacked up the truck and spun the tires with the vehicle in gear and I cannot see any up and down movement. I placed a jack stand near the tires and there is very minimal deflection in the tires.

I removed the tires and checked the runout with a dial indicator on the axle flanges and there is no extreme movement.

At this point I am stumped. Could a rear axle bearing have gone "flat" from sitting in the winter time over the years with the weight of the camper on it? Could an axle be bent, or perhaps the entire housing?

Has anyone encountered a similar situation or know of a link to a write-up or forum thread that discusses a similar problem, even if it's regarding a different vehicle?

I would really appreciate some help or advice.

Thanks very much in advance.

Sincerely, BluegrassPicker

At this point I am stumped. Could a rear axle bearing have gone "flat" from sitting in the winter time over the years with the weight of the camper on it? Could an axle be bent, or perhaps the entire housing?


Yes to all of that, if the vehicle is ever going to sit for long periods you should not have a load sitting in it.

I would assume an axle shaft first, but its all possible.

I'd separate the leaf pack and look for a broken one

that wont make them move like that, leaf springs do nothing but help with heavy loads.

I wouldnt think axle shaft since he checked runout. I would lean towards the bearings. Maybe take a straightedge anf try and check the housing. Thats free anyways.