Pinion angle corection help
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From: Lone Pine
Pinion angle corection help
Finally got my 96 f250 on the road after being down most of the summer. I have a rear driveline vibration starting at about 55-57 MPH. I had swapped in a king pin Dana 60 in the front with cross over steering. In the rear is the stock 10.25 Sterling. I did a shackle flip and the blocks with a 4* built-in taper from Sky Manufacturing to correct the ride height in the back.
=leftI checked angles tonight and came up with transmission output angle 7.3* down, driveshaft 11.9* down, and the rear pinion points up at 15.6*. If I did my math correctly my operating angle at the transmission is 4.6* and 3.7* at the axle. Would this be enough to cause a pretty good vibration at highway speeds? How would I determine what degree shims I need to bring the u-joints into phase?
Best Regards
Richard
=leftI checked angles tonight and came up with transmission output angle 7.3* down, driveshaft 11.9* down, and the rear pinion points up at 15.6*. If I did my math correctly my operating angle at the transmission is 4.6* and 3.7* at the axle. Would this be enough to cause a pretty good vibration at highway speeds? How would I determine what degree shims I need to bring the u-joints into phase?
Best Regards
Richard
Lead Driver
Joined: Feb 2013
Posts: 5,006
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From: Roseville, MN
If I'm understanding you correctly you've done the math wrong. The goal is to have the trans output and the pinion shaft parallel with each other (assuming single Cardan U-joints on both ends of the driveshaft). So if your trans is pointed down 7.3 degrees then your pinion should be pointing up 7.3 degrees, not 15.6 degrees. So yes, your operating angles are 4.6 and 3.7 degrees, but they are in the same direction, not opposite directions as they are supposed to be. So your actual difference is found by adding those numbers, not subtracting them, and you are off by 8.3 degrees. And yes, that's plenty to cause vibration.
You need to turn your pinion down by 8.3 degrees. And you don't need to know the driveshaft angle to figure this out. Subtract 7.3 (what the pinion should point up) from 15.6) what it does point up) and it gives you the same thing.
You need to turn your pinion down by 8.3 degrees. And you don't need to know the driveshaft angle to figure this out. Subtract 7.3 (what the pinion should point up) from 15.6) what it does point up) and it gives you the same thing.
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From: Lone Pine
Ok first the drive line is a simple single u-joint on each end (no CV). I changed the lift blocks around which rotated the pinion down 8* and rechecked the numbers. I'm now showing the t case down 7.2* 14.1* on the drive shaft and the pinion pointed up 6.5*. that gives me .7* for the pinion to rotate up for acceleration and the operating angles are within .5* of each other. I haven't had a chance to drive it yet but it should be good and I should know tomorrow. Thank you all for the help, I now have a better understanding of this whole pinion angle thing.
Richard
Richard
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Joined: Sep 2005
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You want the transmission output to be within a degrrd of parallel to the axle input. With no engine load you may need a degree or so of correction to allow for spring wrap. Sounds like you are in good shape now.
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