"Thumping" Vibration in 89 Caravan

[chryguy]

Howdy,

The Caravan's developed a "thumping" vibration over a couple weeks time, and then perfected it on a recent longish trip.At speed it was quite pronounced, but at low speeds you couldn't really feel it.
It's slowly gotten worse over a distance of a couple hundred miles, and now you can feel it at even low speeds, like when driving around town.

Had another TM guy riding with me for the trip...he was kinda puzzled too.
Kinda' felt like an inner CV joint so...

I installed a new short axle. No difference.

I installed a new long axle. No difference.

No scrape marks on the old axles like they were making contact.

Checked the engine mounts. They don't look like new, but they look good enough. Certainly not shot.

The shims are in place under the passenger side engine mount.

Tie rod ends are good (inner and outer).

Strut mounts are solid, but a little squeaky.

Tomorrow I'm going to inspect the tires. It seemed like a rotational vibration...so I wonder if it could be a broken belt.
I haven't encountered a tire with a broken belt for 25-30 yrs, but I guess it still happens.
I didn't check them first because they're relatively new...maybe two years old, with less than 10K on 'em.

Any ideas? Anything obvious I overlooked?

Thanks in advance,
CG

[RoadWarrior222]

Get the tires / balance checked out..

Also it has only just impinged on my consciousness the last year or so, that wheel bearings can make noises other than a steady groan or squeal and get hot. That would be the classic wear failure, but they also have failures from water intrusion, which causes pitting from rust, and odd knocking noises that you wouldn't expect from wheel bearings normally. This can happen at any time in the bearings life, due to being run through water, or heavy rain, or odd slush/snow conditions, (particularly common on neons and PTs) so you can get a bad one on a bearing that's only a year old or so. As opposed to expecting them to last x years.

[chryguy]

Thanks for the reply...

Changed out the tires one by one with a known good set. Of course it was the last one I changed...doh!

Belt was so bad that when I grabbed the tire, I could feel it. The tread was actually twisted and distorted.
It must have ended-up at the bottom every time I stopped, cause I kept looking at them and didn't see anything.
Course I was looking more at the sides for a bulging sidewall than bulging tread, but it still would have been hard to miss.

Anyway, thanks for the input...she rides smooth as silk now.


CG

[RoadWarrior222]

Glad you found it.

Tires seem a lot more prone to bulging/separation than they used to be, guess it's the cheapy ones. Bad China, no cookie.

[turbovanman²]

What brand of tires?

Usually a tire like that will vibrate.