Another pinion angle question

[cornerstone]

I think I know what the right thing to do is, but I’d rather have y’alls brains in on this as well. Here is the situation... I went to a local driveshaft shop in town and inquired about ordering a new driveshaft with a slip yoke for my 6L80E. After our discussion he told me I need to have my pinion angle set at ride hieght before I measured for the driveshaft, since the length would change as the axle rotates either up or down. That sounded smart.... so here’s what I have currently.
My differential is angled up 7 degrees and my transmission is angled down 4 degrees. Since it needs to be within .5- 3 degrees of parallel, I think there may be 2 or 3 options here. The first is to shim the differential down 5 degrees. The second option is to drop the tail of the transmission another by 2 degrees. Or there’s the third option which would be to find a compromise between the two. Am I way off here? Thanks in advance!
Brian

[mongocanfly]

4deg down on the trans isn't terrible...but the diif needs to match the trans angle.. if you could drop the diff 3deg to make it 4deg, it would be good...I wouldn't try to make the trans match the diff....to much angle
the 3deg up/down is just kind of a unsaid rule of thumb for driveline setup..
do you have all your body on the truck? if your on trailing arms that angle will change when under full load of body

[cornerstone]

Originally Posted by mongocanfly

4deg down on the trans isn't terrible...but the diif needs to match the trans angle.. if you could drop the diff 3deg to make it 4deg, it would be good...I wouldn't try to make the trans match the diff....to much angle
the 3deg up/down is just kind of a unsaid rule of thumb for driveline setup..
do you have all your body on the truck? if your on trailing arms that angle will change when under full load of body

Thanks Mongo! Just the man I was hoping would answer. These measurements were taken with the frame level on jack stands at what I am guessing ride height to be. This is the first truck I’ve done with air ride, and the variable hight is requiring more brain power than I can muster to figure this out.
Brian

[Willie Makeit]

don't worry about the variance, just measure at ride height. the rear end should have parallel angles to the trans. 4 degrees down at trans = 4 degrees up at rear end.

EDIT for clarification: this is in regards to a 1 piece driveshaft only. 2 piece shafts are a whole new can of worms.

[Captainfab]

If your truck has trailing arms and 2" drop blocks, these will solve your angle problem.

http://www.67-72chevytrucks.com/vboa...d.php?t=782895

[cornerstone]

Thanks Willie Makeit, thanks Captainfab. Currently I don't have lowering blocks on the truck, so I probably will get a set of those from you Captain. Do you offer any other angles besides 2.5 degrees?
Brian

[scoot_mcgrute]

I used this article as a guideline for my pinion angle. Basically, you want the total angle at the differential to match the angle at the transmission. I have no vibrations up to 130 on the dyno using this method.

https://www.quickperformance.com/Pin...9gsB0TthqnQBJs

[Captainfab]

This one set of 2.5* blocks is all I have. A local guy I know needed something to correct a pinion angle issue, so I made 2 sets.

Originally Posted by cornerstone

Thanks Willie Makeit, thanks Captainfab. Currently I don't have lowering blocks on the truck, so I probably will get a set of those from you Captain. Do you offer any other angles besides 2.5 degrees?
Brian