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Author Topic:   Pinion U-Joint Mount Damage
Dirt Full Roller

Total posts: 52
posted July 21, 2005 11:58 AM  
We're experiencing contact between the drive shaft and pinion u-joint mounts under deceleration and braking. Pinion angle is 7 degrees on DW-9. Pull bar is BSB spring type with a biscuit rebound damper. We're thinking the rubber biscuit is allowing the pinion angle to increase too much and causing the contact. Anyone had this problem, and if so, what seems to be the fix? Thanks in advance.

Dirt Maniac

Total posts: 180
posted July 21, 2005 11:05 PM  
My buddy had this problem too, but it wasn't a pullbar problem. He had a new driveshaft made, and it had a smaller diameter yoke on the new shaft. It also had 2 small ridges cast into the yoke assembly right where the U-joint girdles needed to move through on deceleration. We took a small die grinder and CAREFULLY radiused the driveshaft yoke down, and cleaned up the casting ridges, and now it doesn't hit anymore.

I'm not saying this is your problem, but it might be something simple you can check on.

What kind of brake biscuit is on your pullbar, and what rate of spring? 7 degrees of pinion angle shouldn't be too much. Also, what kind of down angle is in the pullbar?

Dirt Full Roller

Total posts: 52
posted July 22, 2005 09:56 AM  
The biscuit is a red pull bar biscuit with a bunch of preload. Spring is AFCO progressive, and the angle is about 25 degrees. We did the careful grinding, and checked the damper shock. I know 25 degrees is a lot, but the driver insists on having the early bite. I'm thinking of changing to a harder black biscuit and moving the damper shock rear mount forward so it will bottom before the pinion angle gets extreme.

Dirt Full Roller

Total posts: 33
posted July 23, 2005 06:45 AM  
A 10/90 bilstein fixed the problem for us.

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