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Question for the pinion angle gurus

Richard Cranium

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My driveshaft angle is 2 1/2 degrees. Placing the degree tool on the U joint mount, the rear end is pointing downward 1/2 degree. What size shim do I need to place on top of the springs?

1969 Barracuda.

Thanks. :thumbsup:
 
This might be a little long-winded, but....Forget the driveshaft angle... On our cars what counts is the angle of the centerline of the transmission output shaft, in relation to the rear pinion. Pinion *should* be somewhere between 3 and 5 degrees down (and opposite) from the trans angle, on a (leaf spring) car with the suspension at rest. I know this gets debated (argued?) a lot but this is the right way. It's how the factory figured it as well.

For example... if the trans is pointing down 1 degree, aim to get the pinion pointing down 2-3 degrees. It's like the positive-to-negative number line in math class....If the pinion is down 2 degrees, and it moves up 3 while cruising, that puts it 1 degree up, which is the same angle as the trans being 1 degree down (=parallel angles). It does always move around, so a "close" estimate to parallel while driving is good enough in this case.

You just don't want it to be near parallel at rest with a down-angle on the trans..or worse, pinion pointing up at rest...

And I know you know your stuff....but as an option to getting confused by the "this is how I do it and it works fine" internet crowd, you could give Cass Eslick (the Dr. of Diffs) a call...he'll help you get it right without the noise.
 
Agree with beanhead. All you are really concerned about is the angle of the rear end pinion and the trans tail shaft angle. Cass got me straightened out several years ago when I thought I had pinion angle issues. I don't know if he is answering his phone yet (wish he would) because it would be far easier for him to tell you what you need to do that way. I have ordered a few things from him recently, but we just emailed back and forth.
 
Oh and...when did you get an A-body??

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:p:p:p
 
This might be a little long-winded, but....Forget the driveshaft angle... On our cars what counts is the angle of the centerline of the transmission output shaft, in relation to the rear pinion. Pinion *should* be somewhere between 3 and 5 degrees down (and opposite) from the trans angle, on a (leaf spring) car with the suspension at rest. I know this gets debated (argued?) a lot but this is the right way. It's how the factory figured it as well.

For example... if the trans is pointing down 1 degree, aim to get the pinion pointing down 2-3 degrees. It's like the positive-to-negative number line in math class....If the pinion is down 2 degrees, and it moves up 3 while cruising, that puts it 1 degree up, which is the same angle as the trans being 1 degree down (=parallel angles). It does always move around, so a "close" estimate to parallel while driving is good enough in this case.

You just don't want it to be near parallel at rest with a down-angle on the trans..or worse, pinion pointing up at rest...

And I know you know your stuff....but as an option to getting confused by the "this is how I do it and it works fine" internet crowd, you could give Cass Eslick (the Dr. of Diffs) a call...he'll help you get it right without the noise.


So in other words, the rear end should point down 2-3 degrees?
 
I never checked mine, don't know if I should.
But in case of an adjustment needs to be made, you shim between the axle mount and the leaf springs if I understand correct?
 
So in other words, the rear end should point down 2-3 degrees?
Yeah that's usually safe, as long as there isn't some funky angularity on the transmission, like if it was monkeyed with for racing or something. Stock chassis, should be good.
 
My driveshaft angle is 2 1/2 degrees. Placing the degree tool on the U joint mount, the rear end is pointing downward 1/2 degree. What size shim do I need to place on top of the springs?

1969 Barracuda.

Thanks. :thumbsup:
The only thing that matters is that the trans shaft angle matches the pinion shaft angle, then you set the pinion down at least 1 degree. The actual down or up angle, or driveshaft angle does not matter until the driveshaft gets over about 3 degrees, like on lifted trucks, that's why you need to be careful with the 3-5 degrees down on a street driven car vs a drag car. Anyway if you level your car at all 4 corners by the rockers panels, with the full weight on the wheels, then you can tell if the trans is 1 or 2 degrees down, and what the pinion is and go from there if exact numbers are your thing.
 
IIRC, cass has a chart/diagram on his site.....been awhile since checking it.
 
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