Z28 Boy

i also posted this in the tranny/drivetrain section, but thought i would get more exposure here...so, sorry if you saw it twice.

ok, for some reason, i am having a heck of a problem understanding exactly how to set the pinion angle on my spohn TA.

the directions say to subtract the reading of the pinion from the reading of the driveshaft, and that is the pinion angle, for which i am looking to get -1 degree.

here are two pics of the indicator, taken from the passenger's side of the car...



and...



now, if i am reading the directions correctly, i take the driveshaft angle which is 2.5*, and subtract from it the "pinion" angle, which is 3.5*. that gives me -1*.

is that correct? or are the readings taken relative to something else? if you have any light to shed on this, PLEASE help. i have done a couple searches, and havent gotten any concrete answers. thanks...

-brian

AGood2.8

Remove your driveshaft first.

Then load the rear axle onto jackstands- car must be with axle at ride height to set pinion angle.(It can be jacked up in the rear by the axle only)

Next, measure Transmission rear output shaft height in reference to the underbody chassis. (You will need to reference this exact measurement after you remove the tailshaft housing because the anle of the output shaft will drop and change angle when the tailshaft housing bearing is no longer centering it.

Now remove the tailshaft housing and re- reference it to its original angle with the marks on the block of wood.

Match the pinion angle to the outputshaft angle, then drop the front of the differential down -1* to compensate for thrust. ( under excelleration, the diff will thrust upward under power thus matching the angle of the diff to the angle of the output shaft. This cancels out any bad harmonics- angles need to match under thrust load.

AGood2.8

The reason you dont reference the driveshaft is because its angles are different if the car is lowered. The examples below will show the change in driveshaft angles based on ride height. not the angles of the trans to diff are always with the diff -1*.

Z28 Boy

ok...that makes a lot of sense.

my only question now, is that is there any way of doing this adjustment without removing the tailshaft?

i just spent a LOT of time changing my speedo gears, installing a new tranny pan, and installing the torque arm, and i would HATE to have to remove the majority of that stuff to have to do this.

is there any "plane" on the tranny that i can use as a reference to the output shaft? for example, is there a flat part of the tranny that i can use the angle finder on that there is a known angle between it and the output shaft?

i have heard that the "stock" (i.e., before stock motor and tranny mounts start to sag) angle of a tranny (and engine for that matter) is three degrees down towards the rear.

just trying to get an easier way out. if there is no other way to do it, i wish that i knew about it before, and that there was a mention in it in the instructions for the torque arm.

thanks again man...you are being VERY helpful.

-brian

AGood2.8

If you want to get things dead accurate then thats the best way.

The trans pan is suppose to be paralell with the output shaft but dented pans and bad casting are not reliable for accurate measurements. You can try it. Then when you test drive the car, just make sure the is no "wah wah " or vibration and you are fine.

Note: Driveshafts can show bad vibrations simply from using a more solid trans mount. So sometimes you will get noise from changing from rubber mount Tq arm to solid mount TQ arm and develop vibration (one that didn't exist prior to the mount changes.)- but usually only with the steel driveshafts/ not aluminum.

Z28 Boy

well, my tranny pan is brand new, so hopefuly that can be used as a reference. i will do some research and see what i can find out concerning the angles of that, or other parts on the tranny that may be used. thanks a lot man...

af anyone else has anything to add, please don't hesitate to do so. thanks.

-brian