Vibration At 3500Rpm

[firemac]

Vibration through the floor of a car is often caused by the rear wheels being out of balance. I know that this doesn't entirely align with the observations but it may be worthwhile getting the wheels balanced for the modest cost involved. Presumably the prop-shaft UJ's and support bearing have been checked and that all the exhaust mountings are in good condition. I'm not suggesting that these items may be the sole cause of the vibration but quite small deficiencies can often be the cause of setting up a harmonic which is then magnified by another issue.

Additionally, tyres can become out of round or the compound can become inconsistent, either through manufacturing faults, mis-use or through the tyres flat-spotting as result of vehicle standing idle for long periods, which can set up vibes and/or pulsating noise in the cabin.

Our 3-dr 4.2 suffered from this and a new set of tyres effected a complete cure.

[ALake]

I can understand what you're saying about tyres, but wouldn't that cause vibration at certain speeds? i.e the rotation of the tyre causes the imbalance? This vibration is wholly related to the engine speed not the road speed, so I can replicate it by driving hard and hitting it in lower gears, or simply a higher top speed in 5th. As for the propshaft etc being checked, I wouldn't bet on it - the last time it was in I don't even think they drove the car so I doubt the inspection was very thorough!

When I get a dry mild day I'll get myself underneath and around the engine bay to inspect. I'll check the obvious things first which is what I'd expect a mechanic to do.

[gjnorthall]

I did say that wheel balance doesn't fully align with the symptoms experienced. However the band between about 65 - 80MPH is commonly where wheel imbalance has the maximum amplitude. In addition other things can set up a harmonic which is then amplified. Given the modest cost - it's worth balancing the rear wheels. Get the tyre depot to check for runout and circumferential out of true whilst the wheel is on the balancing machine.

[ALake]

Its probably due some new tyres on the front in a couple of months so I might get that checked then. They're all geolanders in good condition but you never know!

[firemac]

Its probably due some new tyres on the front in a couple of months so I might get that checked then. They're all geolanders in good condition but you never know!

The duff ones on our 3-dr were Duelers and they looked OK as well. Bearing in mind that I'd always had Duelers on our other RAV 5-dr for the previous 9 years, I found it hard to believe that they were responsible for the problem.

Neverthelss, a new set cured the problem completely. Shocked & stunned? Moi? Absolutely.

[ALake]

Cheers for all the info - it will help with my diagnostics! The tyres are in good nick, but probably not much less older than the car so it might well be a factor.

[firemac]

Cheers for all the info - it will help with my diagnostics! The tyres are in good nick, but probably not much less older than the car so it might well be a factor.

I'm not suggesting that two situations are the same but, for what it's worth, our original tyres on the 3-dr looked absolutely fine but despite that, they were clearly the cause of the problems we were experiencing.