Pinion Angle

deuce_roadster said:
I adjust the pinion angle by having the rear axle tubes clamped to the springs but not welded to the housing yet. Should be close to the same degree but oppisite direction of what is at the trans. You can rotate the rear axle and make side to side adjustments also and then weld the pads that sit on the springs to the housings when you have the angle you want.
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Basically this is the samt theory without cutting off the perches and rewelding. That's exactly what I did when I put the car together, but because the engine/trans angle has changed, I need to make the correction.
 
The shims aren't overly expensive so maybe I'll get a thinner set and see what that does.
I'm also wondering if I should have drove the car a little after I installed the shims to see if they settled in after a ride. I don't think that would be the case as everything was bolted down correctly, but at this point what could it 've hurt
 
I just did this on my 55 brand x car installing the 9" rear, and with everything clamped real tight with the U bolts I did move the car gently around in the driveway, so it was all working while sitting on the suspension. Checked again while sitting on the tires before tacking and then welding the pads to the housings. Didn't drive it out on the road.
 
I believe if you are trying to make up a certain shim angle you will have to add up (or subtract depending on a front or rear location for the thick end of the wedge) to get the cumulative angle. That is if you have a 2 deg angle now and add a 3 deg shim you are going to end up with either a 5 deg or a -1 deg. I hope I am understanding your problem correctly.
 
Don T said:
I believe if you are trying to make up a certain shim angle you will have to add up (or subtract depending on a front or rear location for the thick end of the wedge) to get the cumulative angle. That is if you have a 2 deg angle now and add a 3 deg shim you are going to end up with either a 5 deg or a -1 deg. I hope I am understanding your problem correctly.
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Hi Don, the problem I'm having is with the size shim I'm installing, in this case 2 1/2 degrees, is not the same angle I'm getting at the pinion when installed.
From what I've read and watched, whatever degree you need is the size you install. In theory if I need 2 1/2 degrees, I install a 2 1/2 degree shim resulting in raising or lowering, whichever you need, the pinion angle 2 1/2 degrees. What happened for me is I need 2 1/2 degrees and installed a 2 1/2 degree shim and ended up with 5 degrees at the pinion, not good.
I hope this helps paint a clearer picture of what's happening
Thanks
 
“I'm also wondering if I should have drove the car a little after I installed the shims to see if they settled in after a ride.“
I don’t know if it makes any difference, but this was my question in post #9........Mark
 
So your front angle is 3 degrees down and your rear yoke is 4 degrees; is the rear 4 degrees up or down??
 
Without any reference to torque reaction or axel wind-up, if you want the trans output shaft and the diff pinion shaft parallel (which is what is the objective here) they must be at the same angle. If the front is down 3 degrees the rear must be up 3 degrees! So if your rear is up 4 degrees (which I believe is what you are saying when you use the term positive) the it has to come down 1 degree so both are parallel. I believe somehow you are overthinking this as I cannot see how coming up 6.5 degrees, which it seems you are trying to do is going to get the correct result.
 
Don T said:
Without any reference to torque reaction or axel wind-up, if you want the trans output shaft and the diff pinion shaft parallel (which is what is the objective here) they must be at the same angle. If the front is down 3 degrees the rear must be up 3 degrees! So if your rear is up 4 degrees (which I believe is what you are saying when you use the term positive) the it has to come down 1 degree so both are parallel. I believe somehow you are overthinking this as I cannot see how coming up 6.5 degrees, which it seems you are trying to do is going to get the correct result.
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I believe he's saying the pinion is 4/10ths (.4) degree positive now. If the pinion has too much angle with his shim, I think he needs a shim with less angle.
 
Sorry; my apologies for misunderstanding the angle information. Big difference between .4 deg and 4 deg. My Bad.
 
The actual U-joint working angle is what is important, and should be 3* max and within 1* of each other for good joint life and normal RPM. You may have the trans down and pinion up the same (i e 3*), but if the pinion is too high or too low in the chassis, the working angles can easily exceed 3*.
 
Don T said:
Without any reference to torque reaction or axel wind-up, if you want the trans output shaft and the diff pinion shaft parallel (which is what is the objective here) they must be at the same angle. If the front is down 3 degrees the rear must be up 3 degrees! So if your rear is up 4 degrees (which I believe is what you are saying when you use the term positive) the it has to come down 1 degree so both are parallel. I believe somehow you are overthinking this as I cannot see how coming up 6.5 degrees, which it seems you are trying to do is going to get the correct result.
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Don it's point 4 (.4 degrees), not 4 degrees
 
V8 Bob said:
The actual U-joint working angle is what is important, and should be 3* max and within 1* of each other for good joint life and normal RPM. You may have the trans down and pinion up the same (i e 3*), but if the pinion is too high or too low in the chassis, the working angles can easily exceed 3*.
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Again, this is what I'm shooting for, but still can't understand why a 2.5 degree shim would give me 5 degrees at the pinion face
 
jrvariel48 said:
Hi Don, the problem I'm having is with the size shim I'm installing, in this case 2 1/2 degrees, is not the same angle I'm getting at the pinion when installed.
From what I've read and watched, whatever degree you need is the size you install. In theory if I need 2 1/2 degrees, I install a 2 1/2 degree shim resulting in raising or lowering, whichever you need, the pinion angle 2 1/2 degrees. What happened for me is I need 2 1/2 degrees and installed a 2 1/2 degree shim and ended up with 5 degrees at the pinion, not good.
I hope this helps paint a clearer picture of what's happening
Thanks
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J, If you install a 2-1/2 degree shim and have 5 degrees, if you take that shim out, shouldn't you then have 2-1/2 degrees, which is what you want?

You need to measure your engine/trans angle, lets say it's 2-1/2 degrees tail down.
You then need to measure your natural sitting position of the rear axle without any shims. If it is 2-1/2 degrees pinion nose up then you're golden. If it is sitting level or at 0 degrees, then the 2-1/2 degree shim will bring it up.

The shim angle needs to be the DIFFERENCE between the actual angle and the desired angle, not simply the number you are shooting for.

Does this make sense? or have I misunderstood what you have stated?

Mart.
 
Mart said:
J, If you install a 2-1/2 degree shim and have 5 degrees, if you take that shim out, shouldn't you then have 2-1/2 degrees, which is what you want?

You need to measure your engine/trans angle, lets say it's 2-1/2 degrees tail down.
You then need to measure your natural sitting position of the rear axle without any shims. If it is 2-1/2 degrees pinion nose up then you're golden. If it is sitting level or at 0 degrees, then the 2-1/2 degree shim will bring it up.

The shim angle needs to be the DIFFERENCE between the actual angle and the desired angle, not simply the number you are shooting for.

Does this make sense? or have I misunderstood what you have stated?

Mart.
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Mart, let me start from the beginning.
My motor is down 3 degrees
My rear is pointing up at .4 (point 4) degrees
I installed 2.5 degree shims to make up the difference and give me the correct angles.
After all was bolted together and the car was put back on it's wheels, I read 5 degrees at the pinion.
The question is:
Why am I reading 5 degrees at the pinion instead of 2.5??
 
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