Adjusting pinion angle

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Bamamav

Well-known member
Joined
Mar 29, 2012
Messages
6,171
Location
Berry, Alabama
I think I may have screwed up when I set my pinion angle.:( I thought I had it right at 3* up, the tranny is 3* down, so it should balance out. I've got a pretty good vibration above 40-45 MPH, nothing below there. I'm thinking I may need to go back and check it again, going to have to run the car up on some boards level because it's so low I can't get under it.:rolleyes:

If it's off, what would be my best bet on shimming the rear to get the proper angle, buy some of those wedge plates they sell just for that, or just make something work? [S
 
Need to see where the height of the tranny output shaft is in relation to the pinion as well.
in order to do a 3deg down and 3deg up, you would need a difference in height between them.

U-joints in good condition? Did your 3 degree match end up making the driveshaft have no angle on the u-joints at all?
 
Check to see if the driveshaft is bent. Jack the rear up, run the engine in drive and look at it.
Check the u-joints for slop.
Make sure the u-joint is seated in the back yoke good or is the right one.
Make sure the rearend u-bolts are tight.
Check to make sure you don't have a 400 harmonic balancer, flywheel, or both on a 350. I don't think you have to ask me why I'm recommending this :eek:
I'd look at all this before changing the angle. jmho
 
A little more info: U joints are both good no slop, seated in yoke. Rear U bolts are tight. Engine and tranny is stock 75 just as it was pulled from donor as far as I can tell. Angle seems to be more at rear end just by visual check, I have to get the car up about 4 inches so I can crawl under it. I'm thinking that I forgot to put the rear on jack stands before I set the angle, then when the weight went on the springs, it changed the angle at the rear. That's why I hate to stop working on something before I finish, I forget what I've already done sometimes.:(
 
Egg on my face............

Went back and studied the pics I took while mounting the rear. I didn't see the extra set of jack stands under the springs........[S I guess I didn't put them under there when I set the pinion angle. :( Seems like I started one day, and finished the next, so, I goofed up. When I set the car back down on the springs, the pinion angle changed.

Put the car on 2" boards tonight so I could reach under it. Trans is 3* pointed down. Drive shaft is level. Rear pinion is pointed UP 7*. Therein lies my vibration I'm pretty sure. I've got to raise the rear of the spring pad about 1/8" to get the angle close, should end up 3* to 4* up. The drive shaft should end up with a 3*-4* down slope on it when the pinion angle is corrected.

It gets me that I did this. I checked those angles several times before I struck an arc. If I had only put those jack stands in place, it would have been right, but alas, I didn't.

I'm going to go sit in the corner now with my dunce hat on for a while........:rolleyes:
 
Sound enough thinking IDed the problem and you have a fix for it....no sweat man!
My first 10 -15 minutes in the barn is some serious looking around...mostly to remember where I left off...there's stuff to do in every direction.
 
Smooth as silk, well almost.....

Got home early today, so in spite of the 97* temps, I decided to make me some shims for the rear. Found a piece of aluminum I picked up at the terminal that the shop had cut off of one of the trailers. Cut me 4 pieces about 2 inches wide and 6 inches long, drilled a 1/2" hole in one end. Took off the rear tires, loosened the U bolts, put the shims in place and marked the second hole, actually ended up being a notch. Bolted the shims in with the U bolt running through one end and the notch on the other end. Checked the angles again, trans 3* down, rear 2* up, drive shaft, about 3* down to the rear. Took her out for a little road test, almost no vibration now. Got her up to 60 mph a time or two, no longer does it jar your teeth! Probably need to get all four tires balanced and it should be fine.
 

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