Let's Here Those U-Joint Angles

[383gmc]

I know there's been endless discussion about driveline setup, but what I've found is mainly focused on pinion angle. I haven't seen too much discussion about u-joint angles. In the process of converting my '68 GMC SWB C10 from leaf to coil spring I've ran into a problem. I am targeting a 6" drop in the rear, but I'm having trouble with the u-joint angles. From everything I've found the max u-joint angle should be 4 deg. Anything beyond this will reduce life, and potentially cause vibration. The attached chart shows this relation. The attached diagrams show the estimated u-joint angles for a 1 and 2 piece drive shaft at normal ride height with a 6 inch drop for my truck.

One Piece Driveline:

As you can see the u-joint angles are 5.61 deg. This is with the pinion parallel to the transmission output shaft.

Two Piece Driveline:

The front joint is 0.89 deg, which is good. The rear joints are 8.6 deg. This is with the pinion parallel to the front driveline.


Again, all these angles are taken at normal ride height (curb weight). With the suspension at full bottom they will be worse.

My suspicion is that many people are running higher angles in their u-joints with good results. So I'd like to see what everyone is running. If you can, post the following information. I think this would be great information to compile. Thanks everyone.

Vehicle: 1968 C10 SWB
Rear Drop/Lift: 6" drop
Driveline Configuration: One Piece
U-Joint Angles: 5.61/5.61
Comments About Joint Life, Vibration, Performance, Etc: These are estimated values. I have no actual performance information.


Vehicle: 1968 C10 SWB
Rear Drop/Lift: 6" drop
Driveline Configuration: Two Piece
U-Joint Angles: 0.89/8.6/8.6
Comments: These are estimated values. I have no actual performance information.