Setting Pinion Angle

[JOP33]

Probably overthinking this (especially with a 4-Link), but since FFR supplies spacers for the trans mount there has to be some adjustment. Does anyone have a good source for setting up the height of the spacers (angle of transmission) relative to the rearend? FFR tells me that I need an angle of 1-3 degrees. I'd feel a little more comfortable if I had an actual procedure or some instruction to follow on this. Does the car need to be on the ground or jack stands, level etc.? Any help would be appreciated.

Thanks in advance.

[HVACMAN]

I am rapidly approaching this point. My plans are (and I hope someone corrects me if I'm wrong) to get the to the rolling chassis point and set the ride height. Then measure the crankshaft angle at the face of the crank pulley, then measure the pinion angle at the face of the pinion yoke. I currently have 1 1/4 " of billet shims between the transmission and mount to get close. The FF spacers were 1.09", if I remember correctly, but that was for the Ford mount. The thing that concerns me is, as you add weight to the car the ride height changes. When completed, if you return the car to the original ride height, do the angles return to the original settings?

[NAZ]

The bottom line is that the pinion angle should match the trans output shaft angle to prevent vibration. There are many variables that make this difficult. As the rear suspension travels through its range of motion the pinion angle may change and if the control links have elastomer bushings these will flex under load also changing the pinion angle. In most designs the pinion angle setting will be a compromise so that it matches the trans output shaft angle under hard acceleration as that is where you can expect an out of phase vibration to be the most pronounced.

View this video to get a better understanding:https://www.youtube.com/watch?v=Idk3BVDVHq4

[NAZ]

HVACMAN, your procedure for measuring angles will work. You can take an angle reading off any surface that is parallel to or at a right angle to the crankshaft or the trans output shaft, and the pinion shaft. We typically set the pinion angle at ride height of an unoccupied car as that is a baseline condition that is easily repeated. Since the pinion angle on most suspension setups will change under acceleration we will need to adjust the pinion angle down some amount to compensate for the rotational movement of the axle under load. Most folks just guess at this or copy what someone else has done. Determining the proper angle can be difficult as you are trying to measure the rotation of the axle under load where the torque applied to the axle rotates the pinion upward under acceleration and the rear suspension will squat under weight transfer which may change the pinion angle as the suspension moves.

On my car I use non-flexible rod ends so to determine the proper "static" pinion angle I have to first determine how much my car squats under acceleration and how much the pinion angle changes due to suspension travel. The latter is the easy part as you simply chart the pinion angle change per inch of suspension movement from static ride height. Determining how much the car squats (or rises) can be calculated or tested under actual conditions. This way you can be more precise in your set-up.

[AJT '33]

The bottom line is that the pinion angle should match the trans output shaft angle to prevent vibration. There are many variables that make this difficult. As the rear suspension travels through its range of motion the pinion angle may change and if the control links have elastomer bushings these will flex under load also changing the pinion angle. In most designs the pinion angle setting will be a compromise so that it matches the trans output shaft angle under hard acceleration as that is where you can expect an out of phase vibration to be the most pronounced.

View this video to get a better understanding:https://www.youtube.com/watch?v=Idk3BVDVHq4

Hey Naz, I learned something new today much appreciated!! You can say I am less stupid today than yesterday!!

[HVACMAN]

HVACMAN, your procedure for measuring angles will work. You can take an angle reading off any surface that is parallel to or at a right angle to the crankshaft or the trans output shaft, and the pinion shaft. We typically set the pinion angle at ride height of an unoccupied car as that is a baseline condition that is easily repeated. Since the pinion angle on most suspension setups will change under acceleration we will need to adjust the pinion angle down some amount to compensate for the rotational movement of the axle under load. Most folks just guess at this or copy what someone else has done. Determining the proper angle can be difficult as you are trying to measure the rotation of the axle under load where the torque applied to the axle rotates the pinion upward under acceleration and the rear suspension will squat under weight transfer which may change the pinion angle as the suspension moves.

On my car I use non-flexible rod ends so to determine the proper "static" pinion angle I have to first determine how much my car squats under acceleration and how much the pinion angle changes due to suspension travel. The latter is the easy part as you simply chart the pinion angle change per inch of suspension movement from static ride height. Determining how much the car squats (or rises) can be calculated or tested under actual conditions. This way you can be more precise in your set-up.

Great Video!! Thanks Naz

[hutchjc1]

I did mine using the TREMEC driveline angle app, easy to use if you have a smart phone, we have used it on several cars with no issues with the results. It's about as easy to use as one could hope for. Just search for TREMEC driveline angle on your apps tab, its a free app and works well.
Jim