Vibration

[DRD]

Hi All,

I'm getting a vibration, which is felt through the seats at around 60-65mph. It's not present above 70ish or below 60. Also its still there with different wheel/tyres, so not due to balance issues.

It seems speed related but not engine rpm. The diff seems OK and the mountings reinforced and poly bushed.

Has anyone had a similar issue? Could it be the prop shaft uj's?

Cheers Darren

[Mike C]

Propshaft itself  out of balance?

[JochemsTR]

Propshaft

[DRD]

34 minutes ago, Mike C said:

Propshaft itself  out of balance?

How do you balance it? Does it just need replacement?

[stuart]

39 minutes ago, DRD said:

How do you balance it? Does it just need replacement?

The old way used to be to fit a hose clip round it and keep turning it round until you found the sweet spot! New props with bigger UJ`s are available from Proptech in Kidderminster.

Stuart.

[Mike C]

I generally punch locating marks in the UJ flanges at each end and take it to a shop to be balanced. 

Edited September 17, 2019 by Mike C

[Peter Cobbold]

My cure was new UJs, no extra balancing. Front UJ had dried out, and worn.

[DRD]

1 hour ago, stuart said:

The old way used to be to fit a hose clip round it and keep turning it round until you found the sweet spot! New props with bigger UJ`s are available from Proptech in Kidderminster.

Stuart.

Interesting  - where do you put the clip?

[Nigel Triumph]

Check the UJs for play first and if in doubt, replace both with HD items. If there's still vibration try the hose clip trick, unless you want to take the easy/expensive approach of having it professionally balanced.

I've balanced a prop on a Spitfire years ago by fitting two Jubilee clips around it, about 12" in front of the diff, just in front of the sliding joint. Start with the heads of the two clips at 180 degrees to each other and experiment by moving them closer together. It's trial and error and may take a few attempts before the vibration disappears.

Nigel

[stuart]

2 hours ago, DRD said:

Interesting  - where do you put the clip?

As Nigel says above, though Ive found one is usually enough.

Stuart.

[DRD]

23 minutes ago, stuart said:

As Nigel says above, though Ive found one is usually enough.

Stuart.

Thanks Guys, I'll give it a go.

It seems more noticeable on a really smooth road?

[Nigel Triumph]

3 hours ago, stuart said:

As Nigel says above, though Ive found one is usually enough.

Stuart.

The idea of using two opposing clips is that an out of balance that's less than the weight of a single clip can still be balanced.

In theory, two clips can balance anything between zero out of balance (clips at 180 degrees), and an out of balance weight equivalent to two clip heads (both clip heads together in the required orientation).

Nigel

[Stagpowered]

I had the same problem on my car when I first had it, and it also knocked out one of the UJs within a few thousand miles. When I came to replace the joints again, I realised the front and rear halves of the shaft were assembled one spline out.

Since I didn't separate the two halves of the shaft when I replaced the joints the first time, it was either like that from the factory or a previous owner hadn't been too careful.

Re-aligning the UJ's cured the vibration problems, and the joints haven't failed for the last 20 years (that should jinx it)!

Neil