Balance shaft diagnosis

[VT2Commie]

I agree. As it's occurring in definite speed bands it looks like it's driven by a resonance- I'd look for an out of balance tail shaft for starters.

I'd concur. Drive shaft issue.

 

[VPRob]

Thanks guys. Still trying to sort it out.

 

[the_boozer]

if the uni is all right try unbolt the drive shaft off the diff yoke and put it on the other way

 

[VPRob]

I think I'm going to take the tailshaft out and get it balanced, 1. because it seems the most likely culprit and 2. because it's relatively cheap and will either get rid of the vibrations or eliminate it as a source.
I threw on a different set of back tyres and vibration was still present

 

[MikeC]

I think I'm going to take the tailshaft out and get it balanced, 1. because it seems the most likely culprit and 2. because it's relatively cheap and will either get rid of the vibrations or eliminate it as a source.
I threw on a different set of back tyres and vibration was still present

I always punch witness marks on the tailshaft flanges when I remove one- so that it goes back in with the same orientation it had when it was taken out.

 

[VPRob]

Tailshaft to Daniel Engineering in Wollongong on Monday. They corrected uni phasing and re-balanced shaft. Re-installed and vibration(s) pretty much gone. To be honest the roads are so potholed and damaged after months of rain that it takes quite a bit of driving to really check it out but I've been driving it for months with the vibrations so I knew exactly what speeds they occurred at and could always feel them coming in as I hit the speed ranges. Now I've got to get used to them NOT being there and stop looking for them when I'm driving.
When bolting up the centre bearing bracket I did find one of the bolts wouldn't tighten properly without the thread jumping. Luckily a new high tensile bolt worked. So the centre bearing bracket not being properly secured may have been a contributing factor.
I also have a question re the rear engine/transmission mount and alignment of the tailshaft but I will put that in a new post.
Now I can enjoy driving an old car that feels like a limo again.