Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (
-   Transmission - Rearend (
-   -   Pinion angle (

pace69 01-20-2005 07:06 PM

Pinion angle
I need to replace the spring perches on my 12 bolt posi rearend in my 69 ss camaro convertible. The pro shop doing it will not weld new perches on without tknowing the pinion angle. I am told that 6* down is correct?:)

bracketeer 01-20-2005 09:52 PM

pinion angle
Sounds steep to me. A g-body is 4 deg. The A body probably isn't any different. If you got lots of HP you can go 5 or 6.

k-star 01-21-2005 05:08 AM

pinion angle
6 deg sounds like way to much to me. If you run a traction device such as the cal-trac's 2to3 deg would be the correct amount. If you have enough spring wrap to need 6 deg then there is something wrong.


Centerline 01-21-2005 07:31 AM

The correct pinion angle depends on the angle of your trans. You'll need an angle finder (available from Sears for about $10) to measure the angle of the rear face of the trans. Once you have that just reverse the angle and you'll have the proper pinion angle. The optimum is for the angles of the trans and pinion to be parallel, however a difference up to 3* will work.

Here's a graphic that shows how pinion angle can effect the operation of your "U" joints.


bracketeer 01-21-2005 08:51 AM

pinion angle
I have read centerline's pinion angle theory on the bulletin board on two different threads. I have read the same theory on other sites as well. The diagrams he uses is concentrated on drive shaft angle. It's called pinion angle for a reason. You measure the angle of the pinion. As you add weight to the vehicle. A trailer for example. The angle of the driveshaft will change. The rear of the vehicle will sag causing the driveshaft angle to decrease. But the pinion angle is set by the leaf spring saddles or four bars, etc. No matter how much weight is added to the vehicle the pinion angle never changes because it is centered on the suspension. However, you do set pinion angle with the full weight of the vehicle. Jacking the car up will alter the magnetic protractor's reading because the whole vehicle is now on a downward angle.

The instructions from South Side Machine for setting pinion angle can be found on the tech page. 01-21-2005 09:15 AM

Center's description has nothing to do with drive-shaft angle per se. The cartoon shows an exaggerated pinion/ tranny output shaft offset for effect but the main message is to set the pinion centerline parallel with the tranny shaft centerline, no matter if there is offset in the centerlines or they are perfectly lined up. The first cartoon is the ideal, but the second is great, and is in fact the norm - look at those cartoon-like 4-wheel drive trucks w/ drive shafts @ nearly 45deg angles. As long as the two shaft centerlines are parallel (and the U-joints are in phase of course), things are fine. The last two pictures are absolutely forbidden if you want the drive shaft under the car for any length of time.

The point being, the question in the initial post is incorrectly configured. 6* down for a pinion angle by itself has no meaning. That measurement is meaningful only if the tranny shaft is 6* up.

Centerline 01-21-2005 07:46 PM

This graphic is from the tech page and is an excellent example of what NOT to do. When you read the fine print it says, "Keep in mind that these pinion angles are for competition." If you set your pinion as recommended in this pic on a street driven vehicle, as Willys36 says your drive shaft won't be under the car for very long.

The pinion angle is NOT what is stated in the above pic. The pinion angle is the angle of the pinion gear as it relates to level, not the angle of the drive shaft.

For any street driven vehicle the angle of the transmission output shaft and the pinion angle should be parallel. For best results the total of the two angles shouldn't exceed more than 6*. Anyone who recommends something different is just plain wrong... unless they're talking about "racing". The setup in the pic above will work for racing because..... Under extreme acceleration there is a tendency for the pinion gear to try to "climb" the ring gear. When this happens the effective pinion angle winds up being roughly parallel with the trans output shaft. Make no mistake about it, this setup will NOT last for long on the street.

For a street driven vehicle the following are the recommended settings.

For a more detailed explanation on how to properly set pinion and driveline angles check out Inland Empire Driveline.


All times are GMT -6. The time now is 02:07 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.