Prop shaft centre bearing.

[GrahamWright]

Original fault was vibration at 30 mph which worsened over a few longish journeys. The housing was disintegrating and the shaft would move up and down quite freely.

Bearing in mind the difficulty I had splitting the spline, I wonder if that had been incorrectly mated originally and then balanced. I confess I did not note the orientation of the male and female parts during disassembly.

The mating is now very smooth with no play.

[Laird Scooby]

Originally Posted by GrahamWright

Original fault was vibration at 30 mph which worsened over a few longish journeys. The housing was disintegrating and the shaft would move up and down quite freely.

Bearing in mind the difficulty I had splitting the spline, I wonder if that had been incorrectly mated originally and then balanced. I confess I did not note the orientation of the male and female parts during disassembly.

The mating is now very smooth with no play.

Did the vibration disappear as you increased speed? Did it repeat at 30mph intervals e.g. 60, 90, 120mph?

Has it disappeared now?

Have you had your wheels balanced recently?

One other thing you could try, remove the bolts from the prop flange on one end or the other, turn the prop through 180 degrees and refit the bolts. If this doesn't bring an improvement, repeat for the flange the other end.

Also worth checking the gearbox and engine mounts too.

[GrahamWright]

Back over the pit again.

I discovered that the gearbox mounting bolt (secures to the crossmember) was loose - in fact, on the point of falling off.

I've not has a chance of taking her for a run since.

She is a big old lump and not easy to move back and forth over the pit (so the wife claims!).

I've bought a hand winch;-

(https://www.ebay.co.uk/itm/8m-Steel-...72.m2749.l2648)

which I will bolt to the pit wall to save the wife's muscles. I need to move the car for access and escape.

[Laird Scooby]

Originally Posted by GrahamWright

Back over the pit again.

I discovered that the gearbox mounting bolt (secures to the crossmember) was loose - in fact, on the point of falling off.

I've not has a chance of taking her for a run since.

She is a big old lump and not easy to move back and forth over the pit (so the wife claims!).

I've bought a hand winch;-

(https://www.ebay.co.uk/itm/8m-Steel-...72.m2749.l2648)

which I will bolt to the pit wall to save the wife's muscles. I need to move the car for access and escape.

That would quite likely cause your problem! Once you've git it tight again, you may have to reposition the prop centre bearing again as i originally described (slacken bolts 1/2 a turn, drive gently up to speed of vibration etc) but hopefully just getting it tight so the gearbox isn't jumping about like a frog on a hotplate should sort you out!

Double-check your engine mounts as wee, if the gearbox has been moving more than it should there's a chance of a ruptured engine mount as well.