Questions and Answers

Ford Explorer: Wobbled, Not Stirred! Q. Hello Vincent, I just came across your wonderful site yesterday and have hopefully resolved one of my two issues being very poor fuel mileage and lack of power with surging until I get it up to speed. I have a 1993 Ford Explorer, 4.0 liter, automatic transmission with 102,000 miles.

At about 62 mph, my truck begins to shake till about 68 mph. The dashboard vibrates and it also feels like there is side to side shake as if I had a bent wheel. Sometimes my steering wheel would shake as if I had warped rotor. I have done many things chasing this problem.

New brakes and pads front and rear, cut the drums and rotors, swapped wheels from my 1991 Ford Explorer, four new tires, spin balanced, new radius arm bushings, new inner and outer wheel bearings, totally checked out all tie rod ends, center link and ball joints, new front shocks.

Put manual locking hubs on, verified that the hubs are in fact disengaged, checked sway bar bushings, put truck up on all four and ran it up with the truck in 4WD. I felt the vibration at 65 but also felt at about 30, a slight side to side shaking.

The front wheels spun true, but the R/R wheel had a slight shake. I swapped both rear wheels to see if it was the wheel but the R/R wheel still wobbled slightly. I removed the wheel and drum and the vibration lessened but did not go away. I re-installed the drum but inside out to check for wobble and to see if the vibration got worse, it did.

Since the drum had about an inch wide chip in the outer ring, I replaced it thinking that it may be out of balance. No change. Touching the brakes while I feel this vibration has no effect. With everything all back together and the L/R wheel NOT turning, only the R/R, the vibration remains.

My questions to you are; could a very slightly bent R/R axle cause this problem and if so, what is the maximum allowed run out in .000"? Could this cause my steering wheel to shake as if my rotors were warped? I have not yet replaced my rear shocks. This is not a posi unit. The axle code on the door panel sticker is 41.

A friend of mine told me that one time he troubleshot a car that had rotors out of balance because the center of the rotor where the bearings go was off center. All in all, it feels as though I have wheel bounce or hop along with a little wobble. Can you help me narrow this down?

Any suggestions you may have will delay my reservations in the local sanitarium.

Sincerely,
Ray
Wobbled, not stirred!

A. I'm sorry, no suggestions. If I wind up in the sanitarium, I want to have some company and you're elected.

Seriously, there is no set specification for rear axle run out. If you have a dial indicator I would consider anything over 0.100" as excessive. One way to check it without a dial indicator is to make four marks on the axle flange, 12, 3, 6 and 9 o'clock.

Then with 12 up and 6 on the bottom, lay a long straightedge on the two marks and to the floor. Make a mark on the floor. Then turn the axle 180° and do the same thing. This will give you an idea how much run out there is. Then you have to use your judgement to tell if it's too much. This is more of a yardstick measurement then exact science.

You can make the same measurements on your other truck and then compare the two. For that matter, you can swap the whole axle. They are both the same. If the problem moves to the 1991 truck, then you will know for sure.