SLOWTBI

yes, yes i know rear end swaps have been covered to death, but this question has never really been asked (as far as i can find anyway)...
when i swap my peg-leg 2:73s out for an '87 IROC rear-end with a posi and taller gears...once i install the whole new rear-end, will my pinion angle be ok??
any insight is greatly appreciated.

Dewey316

it should be the same as whatever you took out, the torque arm sets the pinion angle.

SLOWTBI

so as long as the torque mount on the trans is tight when i take the rear off, the torque arm will remain the correct pintion angle for the rear...sounds easy enough...

but what if i want to replace the torque arm mount??

Dewey316

you'll still be fine, if you are re-using the stock torque arm, it is not adjustable.

the only time you need to worry about pinion angle, is if you have and adjustable aftemarket torque arm. otherwise, even if the pinion angle was not to your likings, you couldn't change it anway.

SLOWTBI

oh...well there we go...

thanks for the reply

abcx09t

Actually, the pinion angle is adjustable on the third gen even when the stock torq arm is installed. The GM service manual tells you to add shims to or remove them from the tranny mount point. The manual evens tells you how much this will change the pinion angle and provides the bolt and shim part numbers. I can email or fax a copy of the manual pages.
Scott

88 350 tpi formula

iTrader: (9)

I never even looked for that! funny I will look next time I open the old sevice manual up

Steve89GTA

abc, can you PLEASE email me the specs for setting the pinion:
slupo@ozzcorp.com

Thanks!

abcx09t

I will send the Service Manual Pinion Angle Adjustment procedure when I get back to work after Labor Day.

Scott

Guest

how do you set it with an aftermarket set up? i'm going to be getting one from spohn soon

383backinblack

ya it does say that, but have you ever had to do it? you shouldnt unless the driveline mis-aligned or the torque arm is bent.

ive been under hundreds of 3rd gens, and ive never seen a shim on a torque arm mount, i asked my brother who's a tech at a chevy dealership, and he said hes never seen one either

if you bolt everything back together the pinion angle will be well within the limits for your purposes.

my pinion angle is set at -4 degrees, but i dont have a torque arm and my rear end is located by the lift bars....which is a whole different story

abcx09t

I put in the Spohn torque arm. Only hard part is putting the aft bracket on the rearend. I actually had to file off the powdercoat to get it to fit. The rest went together like a puzzle since the aft bracket had to be removed from the assy. But hope yours fits right on. Spohn will supply the torque arm / pinion angle gage. It is an adjustable assy with the torque arm nut and bolt. Just adjust their nut/bolt to get the angle. Real easy especially if you have steel drive shaft...the gage is magnetic. Checking the tranny to drive shaft angle is more difficult since the spohn arm I got has the drive shaft loop and the access is reduced. Good luck.
Scott

graebz28

iTrader: (5)

383,

Do you run -4 degrees all the time?? I heard that put allot of stress on the u-joints.

Does lowering the car change the transmission angle?? If the car is lower in the rear (Jamex springs for example) wouldn't that throw off the ride height and would therefore affect pinion angle? Before I installed the spohn T/A, I used the poly mount w/o the spacer plate. I found the total angle to be 0 (or as close as I could be to zero with the accuracy of the dial indicator) Next on my list of tools is a digital angle finder. When I come to the point of setting up my ladder bars, I want to have a little more accuracy than the shaky dial indicator. Only costs about 160.

If you get the poly mount, you could play around with that spacer to try to dial in the angle exact.

graebz28

iTrader: (5)

Spohn said to measure on the shaft and then on the flat surface on the TA that in under the differential. It is allot easier than trying to take a measurement off the trans. Congruent angles are equal.

383backinblack

ya, that about what it should be anyways....some race cars use -5 or -7 it all depends on the setup, between 2-5 degrees is fine for a street car

my angle is -4 and thats where it stays, cause the lift bars are welded to the axle tubes....so you dont have to worry, set it and your done.

the dial angle finders work fine and are alot more accurate than you think....i used the flat part of the differential where the torque arm would be, and the flat part of the driveshaft on the ujoint to find the angle

any change in ride height can change your pinion angle

idrag2

can someone E-mail thoes specs. too........ idrag2@yahoo.com
Thanks alot