I recently had my front crossmember "rolled" to correct a chamber problem. The guy who did it told me that the engine mounts moved closer together and raised the engine a little.

Anyway, I now have a slight vibration around 70 (around 2000rpm). I suspect that when the engine moved up, it changed the transmission to drive shaft angle. If that is true, the pinion angle is now incorrect and needs to be changed to match the new trans angle.

I took some measurements as described in the service manual, and the pinion is angled down about 5 degrees, the driveshaft is level (0 degrees), and the engine is angled down in back about 4 1/2 degrees).

I do not have adjustable rear upper control arms, so I guess I will have to adjust the angle of the engine. I would think that this could be done by either lowering the front at the engine mounts or raising the rear at the trans mounts. It should be easy enough to put a couple shims under the trans mount, but I am worried that the trans might hit the tunnel.

My question is:

1. how can I calculate what the correct trans angle needs to be based on the pinion angle?

2. is there any way to adjust the engine mounts lower? I think they are stock small block mounts.

Thanks,

Charles. You have mail.

Rob

Charles,
The basic principle behind getting the two angles is that you want to two angles to be the same, but opposite. By that I mean if the engine is angles down in the back approx. 4 1/2 degrees, then you want the rear end angles UP the same 4 1/2 degrees. Are you sure the rearend is angled DOWN at the pinion? Usually, the stock rearend is about level or a few degrees up?

Bill C.

Thanks for the replies/emails.

I am pretty sure the rear input shaft is angled down, but not completely.

I first measured it with the angle finder on the u-joint yoke, the way it shows in the service manual, and got 5 degrees up. This didn't seem like an accurate method, since it didn't look square to the pinion.

I then put a socket on the u-joint bearing cap and the angle finder on the socket and got 5 degrees down. This would seem to be more accurate, but I am not sure.

I will re-check it and see if I come up with anything else.

My angles may just be out of wack. I have hotchkis non-adjustable uppers and the car is pretty low (stock sagging springs). It is not "slammed", but pretty low.

I may need to get some adjustable uppers, but I had no vibration prior to having the work done to my frame, so I hope it can be corrected by adjusting the engine.

Any suggestions welcome.

Thanks,