Pinion angle?

To you chassis guys that know your BBF's in stangs. I found that my pinion angle WAS +1 degree. What degree in your experiences work best? I'm dealing with 800+ hp naturually aspirated leaving on a trans brake in a 10.5" tire SN95 Mustang chassis. "Stock style" suspension. Anti roll, adjustable uppers, coil overs, 9" rear. No rubber. Thanks

First of all, how did you get that measurement?

whatbumper wrote:First of all, how did you get that measurement?

Car not level. Rear tires on ramps with full weight. Driveshaft to pinion pointing upward. 3 degrees on pinion from pinion support, 4 degrees on drive shaft according to the degree finder.

Typically the "V" formed by the pinion centerline and the driveshaft should be open at the top. Angle for something like yours would likely want to be somewhere near 2 degrees.

dkp

bosshoss wrote:Typically the "V" formed by the pinion centerline and the driveshaft should be open at the top. Angle for something like yours would likely want to be somewhere near 2 degrees.

dkp

I made a pretty hard adjustment and am now at -3 degrees. Think that is a little too much?

whatbumper wrote:First of all, how did you get that measurement?

Exactly!

Some people do make the mistake of thinking "pinion angle" is only the pinion's angle (car on the ground) in reference only to the ground.....it's not. "Pinion angle" is always the (again car on the ground) combined U-joint operating angle between the pinion's centerline angle and the driveshaft's centerline angle in relation to each other.

The same thing holds true for the front U-joint. The "slip yoke" angle is the (again car on the ground) combined U-joint operating angle between the slip yoke's centerline angle and the driveshaft's centerline angle in relation to each other.

Theses two front/rear U-joint operating angles work in concert with each other to give you the working driveline angle profile. Using the wrong combination of front/rear U-joint operating angles can cause driveshaft phasing/vibration problems for both street/highway cars & strip cars.

soupbean wrote:Car not level. Rear tires on ramps with full weight. Driveshaft to pinion pointing upward. 3 degrees on pinion from pinion support, 4 degrees on drive shaft according to the degree finder.

I'm not 100% understanding your angle descriptions. But using a generic 3* for the pinion & 4* for the driveshaft you get these possibilities.......


If the angles are actually......

(1) the pinion's nose points uphill 3 degrees.

(2) the driveshaft points nose up/tail down 4 degrees.

Then the combined driveshaft/pinion rear U-joint operating angle is "minus 1.0 degrees" (-1.0*)

**********************

If the angles are actually......

(1) the pinion's nose points uphill 3 degrees.

(2) the driveshaft points nose down/tail up 4 degrees.

Then the combined driveshaft/pinion rear U-joint operating angle is "plus 7.0 degrees" (+7.0*)


*********************


If the angles are actually......

(1) the pinion's nose points downhill 3 degrees.

(2) the driveshaft points nose down/tail up 4 degrees.

Then the combined driveshaft/pinion rear U-joint operating angle is "plus 1.0 degrees" (+1.0*)


********************


If the angles are actually......

(1) the pinion's nose points downhill 3 degrees.

(2) the driveshaft points nose up/tail down 4 degrees.

Then the combined driveshaft/pinion rear U-joint operating angle is "minus 7.0 degrees" (-7.0*)

Dilligasdave, you are correct on your equation of my +1 degree!

soupbean wrote:I made a pretty hard adjustment and am now at -3 degrees. Think that is a little too much?

How much the "maximum" total amount of U-joint operating angle allowed is (to avoid causing dangerous U-joint binding/friction) really depends on who you talk to.

Spicer's web site used to mention a maximum of 3.5* U-joint operating angle under load for their U-joints, but a car's peak driveshaft RPM also plays a part too. The faster the peak shaft rpm is, the lower the U-joint operating angle needs to be to avoid/reduce possible U-joint binding/friction from happening.

But like in ancient times, some guys still to this day like to crank in a bunch of pinion angle thinking it's a chassis/suspension "tuning tool" to make a car hook harder/softer. But all they're really doing is "stealing away" some engine power (through increased U-joint friction/binding) from reaching the rear tires at the launch insted of adjusting the launch with the suspension it's self.

After my upper control arm adjustment, the pinion is point downward .5 degree and the tail of the drive shaft is pointing downward 2.5 degrees equaling -3 degrees correct?

soupbean wrote:After my upper control arm adjustment, the pinion is point downward .5 degree and the tail of the drive shaft is pointing downward 2.5 degrees equaling -3 degrees correct?

Yea, that sounds like a combined operating angle of/around -3.0* to me.