pinion angles being out of spec can cause a vibration noise, & push coming off corner

[garvir]

my 88 monte had a hum noise and vibration, after checking pinion and transmission angles, the trans was -6 degrees down, pinion -2 degrees down, eight degrees is way out of spec, 2 degrees is acceptable. this was an easy fix, shim the trans up +8 degrees (3/8" shims), this gave me trans at +2 degees and pinion still at -2 degrees, PARALLEL AND OPPOSITE. i like the 2 degrees differance, gives the bearing enough angle to rotate. some guys at the road race track run 1 degree, and some run at 0 degrees. they figure that with the car bouncing up and down they will get enough angle differances to rotate the bearing, i guess they are right, never seen a ujoint bust. NOW I HAVE NO HUM NOISE or VIBRATION.

to check angles get car level, when you are checking first thing is to make sure your ujoint is STRAIGHT (VERTICAL) up and down, (inportant) TURN your angle meter cross car, i go off the caps, cause it is hard to find parallel surfaces to the pinion and trans tail shaft.



BOB BOLLES (circle track mag) has had several articles about driveshaft angles.

[MAGONSTERZ68]

1968 Camaro Convertible
Hotchkis UCA - Detroit Speed LCA - Hotchkis 600 LB rate springs front - 178-180 lb leaf spring rear
Hotchkis tuned fox shocks front and back
18" wheel, 275 35 18, 25.6" diameter - 3.5 drop in front - 3" drop in rear, 8.5 GM 10 bolt, 4l65E, zero vibration.
Front ride height measured from fender lip is 25.25 front and 25.75 rear
No odd harmonics accelerating or decelerating and none present at cruising or freeway speeds.

Driveline angles are backwards due to lowering of vehicle?
Engine,trans is 2.6 down - driveline is 2.9 up - pinion is 1.2 down with the pinion angle above the trans/driveline ride height.
Should i try and correct to eliminate the 5.5 and the 4.1 working angles?
if so how best to proceed?

[badazz81z28]

^^ I have played with that app before and results are not repeatable. I don’t trust it.

[icemanrd19]

So your drive shaft goes from the front up to the rear? If so you have a 5.5 front operating angle and a 4.1 in the rear. If you lower the rear pinion angle down alittle the rear operating angle and front operating angle will decrease and get closer. For instance if your engine is 2.6 Dow a nd you move the rear pinion down to say 2.3 my guess is that the drive shaft should flatten out some. Let’s say the drive shaft is now 2 degrees up instead of 2.9 your front operating angle would be 4.6 and rear of 4.3. Much closer matching operating angles