Vibration hard acceleration at 80-100km

[FickleLife]

I was accelerating hard in my 66 from 50kmh to 100kmh and experienced quite a bit of vibration at about 80-90kmh when foot to the floor. Backed off and the vibration stopped - it feels fine lower revs but what would the cause be? Probably need to balance the tail shaft.

Does anyone have any suggestions for what it could be and if it is tails shaft balancing, any recommendations in SE suburbs melbourne? Thanks!

[Clubman7]

Universal joints could be worn out.
Mechanic should be able to figure it out.
Tailshaft could be checked.
There is GJ drivelines in Keysborough or Hardy Spicer in Dandenong.

[GLENN 70]

Should only be a uni joint  check the gear box mount too . . Or if your rear springs are shot ,they might be causing the pinion angel to go out .

[pmb0186]

agree uni joint.
if the trans/ gearbox is leaking look at the yoke and bush.

[67 blue]

I've had the vibrations happen to me at 80 - 90 kmh. Looked into every thing that it could possibly be, and turned out to be a steel rim out of wack. Had to replace the rim.