Don Terrill’s Speed-Talk

Hi guys,

Trying to make sure that my pinion angle is set correctly. Had someone else do it and don't trust it. Want to make sure it is correct. Let me know what info you need if any.

Thanks for any and all help

The pinion angle is in relation to the engine/ transmission and the pinion shaft centerlines. Picture looking at the vehicle and at eye level. You will notice that the engine/transmission angles downward. (The output shaft of the trans is lower than the bolt that holds the harmonic balancer in place.) Now if you were to angle the pinion (usually upwards) until the pinion shaft is parellel with the engine/ trans shafts then you would have a zero pinion angle. What is done is the pinion shaft is angled downwards around 1.5°- 3° (in relation to the engine/trans shaft) to allow for differential rototion while the vehicle is under power. (When all is correct the pinion shaft and the engine/ trans shaft will be parellel while under power.)

If this is a jacked up four wheeler, well you cant have your cake and eat it too.

Nope its an 87 regal drag car...thanks for the assistance. I think that I have a better understanding

That method works fine for the scenario you described. What happens when dealing with a typical backhalf car? Big tire, rear end positioned higher in the body than stock, front suspension lowered as much as possible, engine and trans on stock mounts. In this situation, the rear u joint is typically higher than the front joint with the drive shaft level or running up hill towards the pinion yoke. Point the pinion up 3 degrees to make the pinion and the output shaft parallel and the pinion angle goes 3 or 4 degrees positive. Not acceptable in a drag car. In a car built ground up or with the engine/trans relocated, this is all taken care of during construction. In most other situations, it is usually a compromise, but in no case would I want the pinion angle to go positive in a drag car.

For clarity, I define pinion angle as the difference between the pinion and the driveshaft. Call it rear joint operating angle if you like.

CMcAllister wrote:That method works fine for the scenario you described. What happens when dealing with a typical backhalf car? Big tire, rear end positioned higher in the body than stock, front suspension lowered as much as possible, engine and trans on stock mounts. In this situation, the rear u joint is typically higher than the front joint with the drive shaft level or running up hill towards the pinion yoke. Point the pinion up 3 degrees to make the pinion and the output shaft parallel and the pinion angle goes 3 or 4 degrees positive. Not acceptable in a drag car. In a car built ground up or with the engine/trans relocated, this is all taken care of during construction. In most other situations, it is usually a compromise, but in no case would I want the pinion angle to go positive in a drag car.

For clarity, I define pinion angle as the difference between the pinion and the driveshaft. Call it rear joint operating angle if you like.

If the front output shaft/drive shaft is 3° or 4°, it’s even more important that the rear angle be the same. The angle causes the drive shaft to vary in speed through the rotation. The same angle at the rear nulls the variance and smooths the power delivery. As mentioned, this is most important during initial launch so compensate for any wrap up or squat.