How do I determine if I need Pinion Shims

[Arl37]

I have a 69 C10 Fleetside. I put 2 1/2 dropped spindles on the front and 4 Inch dropped leaves on the rear. Both from Performance Online/Western Chassis. The truck also has 1" dropped shackles in the rear. So it has a theoretical 5 " drop. Had tires rotated and balanced today and the front end aligned.
I " think" I have a minor vibration or throb when I floor board the gas pedal. I don't think had this before I lowered the rear.
The truck also has a two piece drive shaft. The Carrier bearing carriage has one hole remaining at the top so i could move the carrier nearing up one hole. The person who aligned it said I should move the carrier bearing up.
The pinion end of gear case has a decided downward tilt. Don't think it was like this before. A service tec at Western Chassis said dropped trucks should have the pinion tilted downward.
Need less to say I am a little confused.
Can someone tell me how to determine if I need Pinion shims.

Thanks

Ed

[Keith Seymore]

You are flying blind until you get an angle gage and determine the U joint working angle between the rear shaft and the pinion nose of the axle.

Ultimately, for a leaf spring vehicle, you are probably going to want the axle nose down between 3 - 5 degrees relative to the shaft (not ground).

http://67-72chevytrucks.com/vboard/s...d.php?t=522180

K

[Arl37]

Very Helpful Keith and thanks. However, the service manual in the attachment is for a one piece drive shaft and mine is a two. Does that make a difference in the calculations?
Also, I am concerned about the angle between the end of the transmission and the carrier bearing at the end of the first shaft. The carrier bearing carriage can be adjusted up or down depending on which bolt holes are used. Any thoughts?.

[tcrist]

Check out this site. It explains it a bit.

http://spicerparts.com/anglemaster/measuring-angles

[Arl37]

Thanks tcrist. I think that answered most of my questions. I found a digital angle gauge at Harbor freight and tool for $29.95.. Think I will get one and check out the angles tomorrow. Once I get the angles figured out it kinda begs the question of what are the factory specs and how do i take into consideration that the 4 inch drop springs will cause the axle to wrap more than a stock spring and therefore the pinion "needs" more angle?
Any idea where the factory specs can be found?

[mechanicalman]

Originally Posted by Arl37

Can someone tell me how to determine if I need Pinion shims.

Thanks

Ed

See pic

[Keith Seymore]

The document I posted said working angles should be 4 degrees or less.

Yes - you'll need to factor in axle wrap because you want the minimum working angle condition during your typical driveline loading.

[Arl37]

I will determine some angle and try to post them with a diagram today. Thanks for all ur comments.