Board logo

Propshaft Alignment
Rosco - 4/6/17 at 02:49 PM

I have a Ford Type 9 gearbox and Sierra IRS differential and wondering about criticality of propshaft alignment and the possible consequences of misalignment. At the moment I have about a 1.7 degrees horizontal offset which is taken up by the front coupling and about 2 degrees vertical offset which appears to be taken up by the rear coupling. Is this within the normal range for the propshaft couplings or should I be worried about it?

I think I can reduce the vertical offset a little by raising the rear of the gear box, and I intend to do this, but cannot remove the offset completely without having new engine mounts made. Similarly I think I can reduce the horizontal offset a little but cannot remove it without moving the engine forward to provide more clearance with the chassis - something I'd like to avoid due to the impact on weight distribution.

If I can reduce both horizontal and vertical offsets to the 1-1.5 degree range and run at this level are there any consequences in terms of durability, vibration, other..?

Thanks

Slimy38 - 4/6/17 at 03:28 PM

General rule of thumb is that some misalignment is actually a good thing, so the UJ's get some exercise. However, the gearbox face and diff face must be parallel in all planes.

Angel Acevedo - 5/6/17 at 05:32 PM

quote:
Originally posted by Rosco
I have a Ford Type 9 gearbox and Sierra IRS differential and wondering about criticality of propshaft alignment and the possible consequences of misalignment. At the moment I have about a 1.7 degrees horizontal offset which is taken up by the front coupling and about 2 degrees vertical offset which appears to be taken up by the rear coupling. Is this within the normal range for the propshaft couplings or should I be worried about it?

I think I can reduce the vertical offset a little by raising the rear of the gear box, and I intend to do this, but cannot remove the offset completely without having new engine mounts made. Similarly I think I can reduce the horizontal offset a little but cannot remove it without moving the engine forward to provide more clearance with the chassis - something I'd like to avoid due to the impact on weight distribution.

If I can reduce both horizontal and vertical offsets to the 1-1.5 degree range and run at this level are there any consequences in terms of durability, vibration, other..?

Thanks



Although 0 angle (paralell) it is desirable, 1 to 1.5 should pose no problem as the juddering would be absorbed by the springyness of the propshaft.
The actual variation in Rotation speed derived from 1 to 1.5 degrees off should be very small to boot.

Regarding durability, how many miles do you plan to put throug on your kit?
Most likely not enough to be of concern.
HTH.