Knocking/vibration

[stuart_k]

Took the traveller out for the first long A road journey yesterday. A few minor issues - according to my satnav the speedo overreads by about 5-8mph at higher speeds which is no biggie, at least it isn't under reading. The timing chain rattle is getting annoying and I think I'm going to have to replace it a some point and I think I need to look at getting a different ratio diff - I keep reaching for 5th gear!

The only real problem is that at around 55-60mph I get a rhythmic knocking or rather vibration as there is nothing audible which is felt through the steering column. If I take my hands off the wheel it can't be felt and my wife as a passenger didn't notice it at all and believe me she picks up on any little problem with the ride! At lower speeds it goes. The car steers well and there is no drift if I take the hands off the wheel. I'm going to check for play in the steering rack, look at the tie rods and check for play. What else do I need to check? I'm assuming it must be something to do with the front axle or steering linkage.

[mike.perry]

The vibration could be your propshaft has gone out of balance, try swapping it with another. There are other cures such as fitting jubilee clips to it and moving them around until you balance the shaft. Also check for play in the u/js.
My 1098 speedo (1408 TPM) is accurate with a 3.9 diff and oversized wheels

[Dean]

I had a vibration at about 35mph and it turned out to be my front passenger tyre is slightly mis-aligned on the wheel. I swapped it with the spare and it has now gone. To check, jack your car up until the wheel is slightly off the floor and spin it, see if the tyre like mine is slightly out of shape to the wheel. Do this with all four. If one tyre is slightly out of shape, swap it.

Of course it might not be this at all, but it's an easy eliminator.

[PSL184]

If you can feel it through the steering you need to look at wheel/tyre balance (or bulges in tyre walls), eye bolt bushes and tie bar bushes.....