Pinion Angle

[Grancoupe]

I was reading a message posted about differentials when Chryco posted a reply that caught my attention. Its about meassuring pinion angles. I thought a pinion angle was dependant of the angle of the tail shaft of the tranny? My issue arose when I had a new tranny built by a reputable guy in the NY area. He built a great unit. But I snapped the tail shaft the second day it was out. The motor makes decent power but a 727 should be able to hold up to most anything on the street. He told me he felt it was the pinion angle was to high. I looked at what he was talking about and gave him the benefit of the doubt. Persanally I think one of his installers may have left a few bolts loose. This is the second time I snapped a tail shaft. The first time was due to the bellhousing bolts were left loose. I should have checked it myself but I didn't have time so I let it go. I had just started running the car with the front leaf spring shackles flipped up side down. It helped with the traction by lowering the car and raising the front spring perches up into the cars frame. Great. But on the down side it also raised the snout of the diff. When I measured the angles from the tranny tail and the pinion there was a 5 degree difference. When I flipped the shackles back to stock it rotated the pinion down to a 1 degree difference. So for all those I haven't lost through all this.... the question is, where did the 5-7 degree nose down thing come from. All the research I've been doing mentions a relationship between the pinion and the tail shaft. This info would greatly help. I have a set of shims I'm ready to put in so I can put the shackles back in up side down. Thanks

[Chryco Psycho]

When you get on the power the pinion climbs the ring gear & the lowest resistance is when the driveshaft is traight with the pinion in the diff , , the leaf springs will "give' under power so by having the pinion nose down 5-7 * it becomes straight as the pinion climbs the ring gear , ideally stopping when straight . Unless you have jacked uop the rear of the car a foot the tailshft anglke should be a very low degree off straight & will not change under power