Need some help with transmission and pinion angle

[crotchss]

Hey fellas, I've searched a bit on here and found posts about pinion angle, but couldn't find an answer to my question. I have solid motor mounts on my SS, which appear to have raised the front of the engine maybe 3/8"-1/2" at most. Lowered my car 2" all the way around. UMI double adjustable roto-joint rear arms and OPGI 2" drop springs in the rear. Moog 5662 front springs with half coil cut and Global West lowers, Speedway uppers and S-10 2" drop spindles. Measuring with magnetic angle finder the frame lays 0* parallel with ground, trans tail points 3* down, driveshaft 3* down (front to back), pinion 1* down. What I am wandering is if anyone has a measurement on how much your transmission points up or down at the tail? And another question is shouldn't the trans be at 0* also or a little up to make my driveline angles correct? I was thinking the trans should be for example 1* up to be equal opposite of the current pinion angle. Am I right in thinking this? All help is appreciated. Thanks in advance guys

 

[darbysan]

Typically the engine/trans combo point down about 3 degrees, and the pinion would point up about 3 degrees to match it. The angle through the engine/trans should be parallel to an angle drawn through the differential. Here's one of the write-ups I used when investigating mine.
http://www.hotrodhotline.com/md/html/dr ... monics.php

 

[crotchss]

So, reading this link you posted and if I am understanding it correctly, I should have 3* of upward pinion angle to be an equal opposite of my downward trans angle? I thought you want to always have the pinion pointed down. Is that right? I would hate to move my angle to 3* positive pinion angle to counter the front and have worse problems.

 

[darbysan]

I believe you are reading it correctly. For older style(non-4 link) suspensions, the rear axle tended to wrap upwards on acceleration, so they set them 1-2 degrees "down" to allow for the wrap-up( meaning instead of 3 degrees up, they might set it at 1 or 2 degrees up, thereby "down" from where it should be). 4 links don't have that wrap issue, but even so the GM manual recommends 1/2 degree difference, so if you have 3 degrees at the trans, you might set the differential at 2.5 degrees.

More info:
http://www.rosslertrans.com/Pinion%20angle.htm
http://www.moparts.org/Tech/Archive/axle/8.html