pinion angles, drop blocks, and ford 9in

[73kay]

hey guys,

saw a post similar to mine, but didn't want to hijack it. I have a 53 3100 running 235/75/r15s with a ford 9 inch rear end 3.50 posi. I made some 3 inch drop blocks and getting ready to weld the perches on the axle once my angle looks good. Here is my question:

Does it matter that the ford 9 inch axle is offset a bit, aka the driveshaft is not centered as it bolts to the axle? I currently have my truck on a driveway with about 3-5 angle incline and when I use my angle finder on the 235 valve cover, I get about 1 degree positive. (My truck is backed into the driveway). Right now I have my rear axle at 0 degrees. I believe the sweet spot was 2-3 degrees with each other right? I just want to double check before I weld the perches on the axle. I also noticed where the bolt that holds the springs together is not perfectly centered but about 2-3 inches forward of being centered. My tires hit if I try and center off that bolt, so I have the axle mocked up about 1in or so behind the bolt head.

Sorry no pics yet, but I will post some tomorrow. Thanks for your feedback!

[mr48chev]

Some guys seem scared of that tad bit of angle but I think the majority of them have issues with anything that isn't perfectly squared and centered and not a real honest issue with the mechanics of that angle. The one thing I can say is that you don't see Fords wearing out U joints with that angle to the drive shaft any more than you see other rigs with the pinion in the center wearing out U joints.

I'd spend my time worrying about getting the up and down pinion angle right and then weld it up.

There is a pretty good tutorial on pinion angle here. http://www.iedls.com/asp/admin/getFi...&TID=28&FN=PDF

[1project2many]

The angle due to the pinion offset should cancel itself out. If the axle is installed correctly it will have a thrust angle of zero degrees and the pinion will be aligned with the frame rails. If the engine and trans are installed correctly then a line drawn from balancer to tailshaft will also be aligned with the frame rails. So as long as both lines are straight with the frame and the frame itself is straight, the pinion offset angles will not be a problem.

As far as the pinion incline, you want 2-3 as optimal. Engineering papers say less than one degree can cause the U-joints to wear early by brinnelling. But I'll tell ya there are piles and piles of 88 and newer GM 4X4 trucks with a front driveshaft angle near zero that go 100k miles before losing U joints. They do brinnel but it takes quite a while.

[OrrieG]

Universal joints are designed to operate thru a range of angles, and work best when they have a little angle. Get it close and do not sweat exactness. The axle will move during driving; acceleration, deceleration (axle wrap), up and down, and even a little sideways if you are running stock springs. I have seen extreme movement on my front and back drivelines off road and drove it for 15 years as a DD with no problems.

[dsraven]

usually the engine angles downward at the rear about 3 deg, and the pinion is set to angle up 3 deg at ride height. so whatever your engine angle is at just do the opposite angle for the pinion and it should be good. the offset pumpkin thing works it's way out the same way. the angle at the front cancels the angle at the back. like orrieg says, a little angle is good otherwise the rollers in the trunion bearings of the ujoint wear a groove into the trunion and then you have issues with vibration etc because the rollers don't want to move out of the groove, plus the ujoint gets a corresponding sloppiness relative to how deep those grooves are.

[73kay]

Thanks for all the advice. I'm gonna check my angles one more time and tack away!