Ring up VPW and ask them for some pinion angle shim wedges. They are a 2 deg metal wedge which is inserted inbetween the diff and the leafs. Insert them from the rear to give a "nose down" angle. Try 2 (1 each side) first.

Interesting, Bert, I didn't know VPW had the wedges. I have been taliking with an ex Ford mechanic, and he has told me that the AU wagons had vibration problems, and they used wedges to deal with it. Maybe I haven't shimmed/wedged the rear of the diff high enough.

Surely there must be an automotive engineer reading these posts that can shed some light on the problem ?

FRom what I understand, the diff+tailshaft has an optimum operating angle. I don't know what that angle is tho', and how does lowering the car 20mm odd throw it out so far. Surely the diff/tailshaft angle couldn't alter that much ?

BTW, thanks falconea !

There was an article in Street Machine mag a while back that had a guy with a wagon that had the same problems. They had to tilt the diff up (or down I cant remember) a bit to straighten the axis to the tailshaft because after lowering it the angle changed and caused vibrations.
They found the problem while it was on a dyno. A guy stood on the tow bar or something and they worked out it was the tailshaft entering the diff at the wrong angle after lowering it.

So I think creeture3 is right in saying about the optimum operating angle.

Bugger, I have thrown out all my SM mags!!!

Can anybody else remember such an article?? If so, I wil gladly pay for a copy.

I should write to SM and ask them

Basically you are not supposed to have the pinion yoke in the same plane as the output shaft of the trans. I believe the reason is the way the unis will get "loaded". Lowering the car excessively will bring them inline.

They should equal but opposite angles of each other so the net result is zero degrees. To fix this you need the wedges inserted in at the rear as I stated earlier. About 10-8deg nose down is good. This can be read with a magnetic angle reader (I think they are called this?) off the yoke.

Also If you lowered the a** with lowering blocks this is a very bad way to do it, especially if the car has some power. It creates a moment or leverage force over the leaf springs and can induce uncontrolled positive pinion angle and wheel hop.

You ripper Bert. That's what I needed to know!!!!!!

I have "shimmed" the diff., but it is nowhere near enough according to your calculations. All I did was put in a 3mm piece of flat bar. this only gave me maybe 2 to 3 deg. at the most. I reckon I can work with what you have said

Now I have to start applying trigonometry. Farcanal, it's been a long time.....

BTW I didn't lower the rear with blocks, it was done with re-set springs, and the car doesn't have enough power (yet) to wind up the springs.

Many, many many thanks,