cmadki4

I bought a used conversion van with 67k miles on it. A few hundred miles into ownership I notice a wobble start to develop. I only ever noticed it around 45-50mph. The whole van shakes violently. It seems like if the wobble is just starting you can tame it by turning the steering wheels slightly left or right.

Local shop said tires look fine, tie rod ends felt tight. They replaced the front discs thinking it may be warp rotors. That didn't change anything. He's stumped so he said come get it and didn't charge me for the brakes.

It has aftermarket wheels from the conversion company. There is quite a bit of curbage on them. Don't know if those could be the culprit? Center bore not concentric?

I'm taking it back to the dealer where I bought it to have them look at it. They are very familiar with the vehicle, because it was their car they used to shuttle customers from the airport to the dealership and the GM used on family vacations.

A couple more observations:
- My garage apron has a tall lip where the driveway has dropped below the garage floor level and I noticed an audible 'knock' from the front right while backing when the front right tire came to that ledge. Could some suspension components feel tight when the car is jacked up and moved with prybar, but then move under the load of the big van?
- The vibration can happen anywhere, but memory serves me it seems to like to start wobbling doing down hill. However, you can feel the beginning/hinting of a wobble from time to time in just about any road condition.

Please help! I has some hands on experience with repairing smaller cars, but limited tools/equipment to check/repair anything myself anymore.

Thanks.

solwav

Wow sounds like a potentially dangerous situation and I am sorry to read about your problem. I hope the dealer can repair your van or at least give you a refund should you want one
Question the "knock" you hear does it sound like a metal to metal contact if so I would suspect the suspension. You wrote the wheels my be the cause, well you could rule the wheels
out by asking the dealer to swap four wheels from another van onto yours then you go for a ride to test if it will wobble.

If you sale included a warranty be sure to know all legal recourse available to you, in my mind your dealer should be doing everything thing possible to sort out your wobble problem
but it seems they are not. Also I believe you mentioned the van was a shuttle van for the company so to me it seems they must be aware of the problem.

canucklehead

"It has aftermarket wheels from the conversion company. There is quite a bit of curbage on them."

I would have started right there. Have the wheels balanced. Maybe one is bent.

cmadki4

I've only noticed the knock once and it does seems staccato enough to be metal on metal, but hard to tell since I was in the car (albeit with the windows down). Good idea on swapping out wheels.

Wheels/tires would appear to be the most common solution when I researched around the interwebs. Even found a reviewer on Explorer Van Co's facebook page with the exact same vehicle and exact same issue. Wheels and tires solved it for him. Also, this guy: 2003 chevy express 2wd wobble - Sportsmobile Forum & https://chevroletforum.com/forum/exp...e-61362/page2/. Same guy, I believe. But that just seems too easy lol.

Then there is this guy who had driveshaft balance issue: https://chevroletforum.com/forum/exp...-55-mph-20210/

I drove the van to work today to take it to dealer (not where I bought it but same family of dealers where I bought my other cars) to have them really go over the wheels/tires closely. EDIT: I have to note that I could not get the wobble to happen on my 30 mile commute. It barely started to rear it's head after hitting a mild bump or 2 doing 45-50, but never did get violent.

cmadki4

UPDATE: Cadillac service center looked at it over, focusing on the front tires/wheels. They did a road force balance, which said one was kind of out and the other was really out of balance. I didn't fully understand, but he said he actually removed the tires from the wheels and remounted them in a more appropriate position.

Over the super short drive back to work I do notice that is drives A LOT smoother. No hint of any vibration, wobbling or movement in the steering wheel. The commute home will be more telling. For some reason, I highly doubt that's all it was given the severity of the wobble, but I'm sure it didn't help.

Could the tires/wheels being out of balance some really cause violent wobble like that? Or could it just be what's triggering the violent wobble? Like bad shock absorber that's allowing something harmonic in the front end to grow and grow into the violent wobble?

solwav

Well a out of balance wheel could easily cause the vibration/wobble you described. Balance your wheels first and be sure the mounting surfaces (back of wheels and face of rotors) are clean.

Then you can locate the origin of the knock.

greenfire

That road force balance is key.. it mimics the tire driving on the road and balances it better than a regular balance. The tire may have been "heavier" on one side and he moved it to balance easier. You may have solved the problem.

Artie1

I have had an exactly the same issue at 45-50mph and it was very bad. Coins were jumping out of cup holders! I was towing a trailer at the moment and if I couldn't pass that speed and accelerate further, I had to brake down to 30mph until it stopped, and try all over again. I can only imagine what the traffic behind me was thinking about the idiot who brakes and holds flow on a straight road.
What helped me is replacing the idler arm, pitman arm and tie rod ends. Basically, the whole steering linkage. Tugging on those things on a car lift with mechanic's hand doesn't show you any wear, as the forces exerted on those joints at speeds are magnitudes higher.

Artie1

Buy parts at Rockauto and take them to any local shop. This design hasn't changed for 50 years if not more, and any experienced mechanic knows how to do that job.

cmadki4

UPDATE: I put a hundred miles or so on the odometer over the weekend and the ride is noticeably smoother. More importantly, I never could get the thing to wobble/shake violently like it was before. It sure seems like the road force balance fixed it. Or at least appears to have fixed it.

@Artie1: I had the same thoughts on trying to tell if something in the suspension is loose by moving it by hand/prybar. Never did seem like a fair test given the loads expressed on those parts on vans of this size sitting still, let alone at interstate speeds. There was a recall or service notice for these van's pitman arms at one point, due to lack of proper hardening and risk of failure. Might have the dealer look at that tomorrow just in case. The wobble seems to have been cured with the road force balance, but I have to go up there to get additional key fobs that were part of the deal.

Thanks all for your input. I'll try to update this thread if anything changes.

Cliff notes: Cure to the 'death wobble' in my particular case was road force balance of front wheel/tire assemblies.