Hot Rods Driveshaft angles?

Hi all my fiberglass 31 ford pickup is almost complete and have begun to drive it. I have a driveline vibration very fast ,so assuming driveshaft. I went to spicer website and used their calculator and this is what I have, tailshaft is 3 degrees down, pinion is 3 degrees up and driveshaft is 4 degrees down toward tailshaft. It gave me a operating angle of about 7 degrees, from that it said it was good to 2500 rpm. My question is I can’t raise the tailshaft any , but is there anything I can do to correct or make the angles better or at least bearable? Thanks in advance, Jim


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The tailshaft and pinion degrees need to be equal and opposite. Sounds like that's what you have. But it's too bad your engine is too much lower than the rearend. I think the only solution is to find a way to raise the tailshaft, then lower the pinion a corresponding amount.

Or raise the rearend. (and check your angles again after you do it)

 

Thanks part of the problem is the frame has about 3 degree rake to it and makes the engine lower than the rearend, just not sure how to handle that. If the frame was level I think it would be easier to correct.


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Why does the frame angle matter ?
The frame is basically out in space.

With the engine/trans. at "its" given/as mounted angle and the "car at full ride height" (fully weighted, one or two people)...so the rear springs are setting as they would be driving down the road, the pinion angle should be the same (nearly the same) as the engine/trans. centerline angle.
Also as mentioned, the difference in the height (or the distance) between the two should be kept to a minimum.

Mike

P.s. - As you jack the car up and set it on jack stands, yes, the frame angle MUST be the same on jack stands as it would be as sitting on level ground.

 

Thanks mike, I mentioned the frame angle to explain why the driveshaft was higher at the rear axle than at the transmission. But I’m unclear what to try since the transmission is as high as it can go so I can’t adjust. The only adjustment i can make is at the rearend,but that is limited as to keeping the angles close to the same,or am I missing a part of the puzzle?


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Hi...I had the same thing, had a vibration when my foot was on the gas up to 2500rpm. take foot off the gas and the vibration went away, so I lowered the pinion 2* worked for me.

 

Thanks, were your angles about the same as mine ?


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