Pinion Angle

jrvariel48

jrvariel48

Well-known member
I know this is better suited for the Hamb, but there's a lot of talented people here on the barn that deal with this problem. When I installed the new motor in my car, I had to raise the motor mounts up to clear the oil pan which was modified for main bearing cap supports. That pushed my angle to 3*. I'm not sure what the original degree was, but I don't remember any driveline vibration. Now I need to correct my rear angle by 2.5*. I purchased the proper shims and installed them yesterday. My original reading at the pinion yoke face was .4*. My 35 coupe has a Ford 9" with parallel leafs from Weedetr. After I installed the shims, I put everything back together and dropped the car back down on the wheels. I climbed under to get a reading, and I was getting 5* of angle on the pinion yoke instead of 2.5.
Can someone tell me what I may have done wrong?
Thanks
 
What is the angle of the transmission output shaft? Are you saying it is 3 degrees down?
 
You’re crankshaft/trans main shaft centerline needs to be parallel with pinion centerline at ride height but not on same plane.
 
How are you measuring the angles - with what device? If you're transmission is 3 degrees down, then typically you want the pinion angle to be 3 degrees up (approximately). Given the torque/twist of the rear (and depending on how it is mounted), usually one will set it up a bit lower - like 1 or 2 degrees as there is usually some amount of upward "twist" under power. This is especially true if you only have leaf springs and no sort of 4-link or other more "controlled" type of mounting system.

Attached is a good PDF on it.

View attachment Tailshaft.pdf
 
Bored&Stroked said:
How are you measuring the angles - with what device? If you're transmission is 3 degrees down, then typically you want the pinion angle to be 3 degrees up (approximately). Given the torque/twist of the rear (and depending on how it is mounted), usually one will set it up a bit lower - like 1 or 2 degrees as there is usually some amount of upward "twist" under power. This is especially true if you only have leaf springs and no sort of 4-link or other more "controlled" type of mounting system.

Attached is a good PDF on it.

View attachment 480128
Click to expand...

I’m using a digital angle finder.
It’s leaf springs only.
The biggest confusion is why the 2 1/2” shims I installed are showing 5 degrees at the pinion and not 2 1/2 degrees
 
jrvariel48 said:
I’m using a digital angle finder.
It’s leaf springs only.
The biggest confusion is why the 2 1/2” shims I installed are showing 5 degrees at the pinion and not 2 1/2 degrees
Click to expand...
Perhaps you should consider that the reading you took initially was erroneous on your part.
 
We’re you at actual ride height? ......had the car been driven after or at least bounced the suspension?......Mark
 
You might need to put the shims on the other direction. The wedge on the other side of the axle. I've done this myself. It looks like you put it on the side it needs to be and it makes it worse instead of better.
 
Scotty's 52 F3 said:
You might need to put the shims on the other direction. The wedge on the other side of the axle. I've done this myself. It looks like you put it on the side it needs to be and it makes it worse instead of better.
Click to expand...

I could try that, but looking at the shim, the thick side should go in front to raise the nose of the rear and in the back to lower it.
Sounds right, but at this point I'm willing to try anything!
 
If I 'm building a drag race car and the trans c/L is 3 degrees down, I set the pinion c/L at 5 degrees down with leaf springs and no ladders. With bars I set rear at 4 degrees. For a cruiser I would start with 4 and see what she wants.
 
jrvariel48 said:
I could try that, but looking at the shim, the thick side should go in front to raise the nose of the rear and in the back to lower it.
Sounds right, but at this point I'm willing to try anything!
Click to expand...
If it has parallel leaf springs, and you put the wedge in the front, wouldn’t that lower the pinion? Imagining it in my head, I think your statement is backwards. I wish I knew how to draw a picture on this thing......I didn’t realize you had been driving the car ( my other post ) I thought the suspension was something you just worked on .......Mark
 
flatford8 said:
If it has parallel leaf springs, and you put the wedge in the front, wouldn’t that lower the pinion? Imagining it in my head, I think your statement is backwards. I wish I knew how to draw a picture on this thing......I didn’t realize you had been driving the car ( my other post ) I thought the suspension was something you just worked on .......Mark
Click to expand...

Haha! Yes it's hard to explain. The wedge goes in between the spring perch and the springs. Try to picture standing in front of the wheel on the drivers side and looking towards the third member. If you put the thick part of the wedge in front it lifts the pinion yoke up. This is the best I could do Lol
 
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.
 
40cpe said:
Do you have the wrong wedges? Too thick?
Click to expand...

I read a bunch of articles, watched youtube videos and checked my chassis books. All of them said install the shims to make up the angle you need. I figured maybe I missed something thinking maybe it doubles the angle, but I found nothing. I checked the shims I bought and they are correct at 2 1/2 degrees
 
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