bullitt ben

Is this correct?

driveshaft angle EX: -1.1
minus -
Pinion flange EX: -0.2
---------------------
Equals:Pinion angle = -1.3

808muscle

I spent months trying to get my PA right. Bought a digital gauge and the manual one. No setting ever worked for me. Even tried two different DS. They all vibrated. Took the DS off and went back to the stocker.
First of all are talking about a one piece DS? My experience taught me measuring the angle depends on whom you talk to. I had the DS manufacturer telling me one way and the UCA guys telling me another. I would suggest doing a search and go from there. Some will say subtrack the pinion number from the trans number. Others will say no thats wrong. In the end, just get under there adjust it and take it up to 80 mph and if she vibrates go back and keep adjusting to you find the sweet spot. If you read old threads you will find this mod just doesnt work on some cars for no apparent reason.

jsimmonstx

Could it be that your upper control arms are adjusted to different lengths, thereby tweaking the rear axle to a non-perpendicular angle to the drive shaft?

bullitt ben

No kidding,

I've read for hours and the more i read the more confused i get ...but the one calculation that seems to stand out the most is substracting the driveshaft angle from the differential pinion flange,

I just recently added a full suspension setup (shocks ,Ford racing front control arms,springs,lower control arms(non adjust), upper control arm (ajust) with mount,sway bars,ect..so when i got car aligned i asked to get pinion angle adjusted.....didn't even want to touch it....so while car was on alingment bench (level)..i measured with Iphone level and got these numbers:

driveshaft angle.... = -1.1
pinion flange angle. = -0.2

so where do i need to put pinion flange to obtain proper pinion angle which i read is around -2 ?

I have an appointment this afternoon to get pinion angle adjusted and want to make sure they get the math right.

jsimmonstx

Seems to me that as the pinion flange angle changes, so to will the driveshaft's angle.

Question - is the pinion angle measure when the car is resting on the suspension, or when the car is on a lift with no weight on the springs?

moosestang

It's always with the suspension loaded, I think everyone can agree on that. I'm in the opposite of the trans flange angle camp myself.

I'm not sure there's a one piece that will ever be as smooth as the stocker. I noticed some manufactures started using the CV joint at the pinion, just like the stock shaft.

bullitt ben

Yes car was on alignment bench with suspension loaded

jpplaw

The idea is that when the pinion torques on acceleration, it wants to rotate up towards the body of the car. When that happens you want the pinion angle to become equal to the driveshaft angle where it leaves the tranny. The tranny angle doesn't change on acceleration, just the pinion does. Complicating matters, there is also chassis squat and suspension movement to figure into the equation.

Suspension full loaded, measure the pinion angle and tranny flange angle, then subtract tranny from pinion. Adjust UCA to change the pinion to what you want. Rule of thumb (but not perfect) is you want the pinion 2 degrees further down than the tranny angle. For example, if your tranny flange is -.5, then you want the pinion to be -2.5. Like I said, the rule is not perfect, but it gets you in the ballpark.

You will never get the tranny angle, pinion angle and driveshaft to ever achieve a straight line because they are on different geometric planes (pinion is lower than tranny), your goal is to get the u-joint angles to match on acceleration.

808muscle

Well said.

Dont pay a shop to do it unless they really know what they are doing and guarantee their work. Adjusting the UCA is really simple. I would do a run down the track then back up on ramps, slide under there and with a 15` cresent wrench adjust the UCA before the next run. Took me 10 minutes tops.