Wobbly ass at 58!

P38 2002 DHSE Auto
Getting a vibration through my bum at 58mph. Doesn't seem to do it before or after that speed just at 58 mph!
I have had a quick look at the prop uj this evening and although it looks a bot brittle and its all there, any suggestions?

Dave

Propshaft universal joints I would think.

Had that myself recently, UJ's at the front were far worse than the back but did them all - no more wobbly ass!

After purchasing mine a few years back I'd get vibration at 55mph only, but enough to shake the passenger seat, completely cured after wheels re balanced.

Start with the simple things, get all four wheels balanced. You might have just lost a balance weight. As for the UJs, try greasing them. If grease ****es out of only one joint on any one (or you can't get grease in) you can assume that it needs changing. If one is doubtful then, for the cost of them, it's probably worth changing the lot.

I didn't know a donkey could run that fast. Or did he mean arse?

In my experience, unbalanced front wheels usually cause vibration through the steering, not sure about the back wheels being out of balance and how you might feel that.

I thought that the rule for vibration in the seat was transmission related.

A vibration can be caused by anything that hits the relevant harmonic. My suggestion about the wheels was because, unless the fault falls into the 'bleedin obvious' category, I always start with the simplest and cheapest investigation. Getting some other bugger to jack your car up and remove, balance and replace your wheels allow you to eliminate wheel bearings (a quick shake before or after wheel removal), wheel balance and loose wheel nuts. Whilst it's up in the air you can have a quick look for obvious bush or other issues.

Wammer, down here in Cornwall were not posh enough to have arse's that's why I have a wobbly ass!

Thanks for all the feedback guys you've given me something to go out.

Dave

My bmw did it with unbalanced rear wheels.

merlinpjl said:

In my experience, unbalanced front wheels usually cause vibration through the steering, not sure about the back wheels being out of balance and how you might feel that.

I thought that the rule for vibration in the seat was transmission related.

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An understandable assumption, but as suggested I'd bet on the wheel balance kicking off a harmonic vibration. Mine was so bad I thought the seat was gonna come off its mountings, after throwing a wheel weight. The only other thing I did at the same time as the re-balance was to ditch the Pirelli Scorpion STR's, but I can't believe a harmonic vibration would be down to those.

Stu

Had the same issue. Replaced a front and rear UJ, Balanced tyres and and had a front brake that had lost a pad. Just ones to go on a good run to check her out now. The props were doing most of the wobbling so worth checking...

60mph is a common speed to get vibration from unbalanced wheels.

clivesP38 said:

60mph is a common speed to get vibration from unbalanced wheels.

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+ 1, 100% the problem