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Van variable vibration

I have a '95 Ford E150 van with 170,000 miles. It has a vibration that feels just like an unbalanced tire, except that this vibration comes and goes about every half mile. The problem can occurs at any speed over 45 mph, but is really bad at 65 mph. I don’t dare drive it faster for very long. It does not cause a torque in the steering wheel, but shakes the whole vehicle side to side. Over several years, I have gone to three shops to have had all tires balanced. Every place I bring it, they find something reasonable to fix like ball joints; exhaust hangers; turn brake rotors; check engine mounts; but the problem is still with me after many years. I have measured the vibration with a laptop and used Audacity to display the vibration frequencies. The major vibration is at the one-per-rev wheel speed. the analysis does show some very slight vibration at the drive-shaft speed. Even so, I am letting the shape that has it now remove the driveshaft to check its balance. I don’t know what this is going to cost me, they have been working on it for three days. I don’t think they will be able to find it.

Does anyone have any good clues?

I got the van back from the shop yesterday. After spending $1,200 for them to check tire inflation, balance all the tires, replace the ball joints and some of the steering linkages, turn the rotors and repack the bearings, align the front, the vibration problem is still there. It is actually somewhat more consistent around 65 mph. Over 70 it is not as bad. But still, at 65, it will come and go. I have a neighbor with a similar van without the problem. He is willing to let me try swapping my wheels for his, to see if the problem goes with the wheels or the vehicle. That will take me a while. That’s 8 wheel changes to swap them, and 8 to swap them back. I don’t know what else to try, or where to turn.

I had a cargo van and had a vibration that caused a rattle. I put a bungee cord on the jack handle to restrain it. Yours sounds much worse. Used vans with 20,000 miles on them can be had for $17,000 and less. One better than yours can be had for a lot less.

It doesn’t make any difference to the vibration, but this is actually a factory passenger van “Club Wagon.” I lost my chance to trade it in as a clunker. I gave it serious thought. One reason was that I wasn’t ready to buy a new one. In true Car Talk style, the second reason was that my wife didn’t want us to junk it just yet. In all fairness to her position, we still have one last daughter to get through college.

The accident that is surely coming will cost you a lot more than a different beater. A frame and body specialist should have a look. Make sure the steering box isn’t loose and that the steering stabilizer (if equipped) is working. Body shop will be looking for rusted out frame, missing body mounts, aft mount on transmission and missing bolts.

Yesterday, I swapped all four wheels with my neighbor’s similar van. His van has no problem with my wheels, and my van has the same problem with his wheels. The only difference is that the vibration is worse at a slightly lower speed (around 63) with his wheels mounted on it. So I know the problem is not tire unbalance, variable sidewall stiffness, or a bent rim. The problem is entirely in the vehicle, not the wheels or tires.

Thanks pleasedodgevan2, I will check for aft transmission mounts. I also suspect something wrong with the rear axle, since the problem is road speed related, and the vibration is at wheel rotation frequency.