Pinion angle shims:

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DesertRat

DesertRat

Leading edge boomer
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My car is a 1967 Barracuda. Stock suspension all around, rebuilt stock springs with the 7 1/4 changed to a 1973 8 1/4 rear axle, no pinion snubber. I am good with stock ride height and I have installed a GV overdrive in the car which extended and lowered the transmission tailshaft. My rear axle pinion angle is 3* up and the transmission is 5* up. (up being up toward the radiator) By my calculations I need to add a 1.5* shim to the rear spring perches to lift the rear pinion angle and bring the delta to within .5*.
Is my math correct and where can I buy an all steel 1.5* X 2.5" wide shim?
All advice read and appreciated------------------DR----------------:)
 
IIRC I bought my last set of correct width shims from Speedway. I think the set was made by one of the major circle track brands. I'm pretty sure they are not steel but have held up well.
 
Today I got My 1.5 degree pinion shims. My pack of six and I need two. Hope to have them installed by my tire/alignment appointment on Monday.
 
DesertRat said:
My car is a 1967 Barracuda. Stock suspension all around, rebuilt stock springs with the 7 1/4 changed to a 1973 8 1/4 rear axle, no pinion snubber. I am good with stock ride height and I have installed a GV overdrive in the car which extended and lowered the transmission tailshaft. My rear axle pinion angle is 3* up and the transmission is 5* up. (up being up toward the radiator) By my calculations I need to add a 1.5* shim to the rear spring perches to lift the rear pinion angle and bring the delta to within .5*.
Is my math correct and where can I buy an all steel 1.5* X 2.5" wide shim?
All advice read and appreciated------------------DR----------------:)
Click to expand...
none of this makes sense to me. ur saying u have 8 up total now, and think 1 1/2 degree shims will put it up more ?
 
This is why I asked for input back when. When I add the shim the rear pinion will have a 4.5 angle and the trans will have a 5 angle which will give me a .5 degree delta between the front and rear spider angle, which is what I am shooting for. If the angles were opposite then they would be additive but judging by the lack of response to my OP, I am guessing this is something that few folks have thought about. As of now I haven't done anything but I am just following the instructions in the GearVendors shop manual at this point.
 
DesertRat said:
This is why I asked for input back when. When I add the shim the rear pinion will have a 4.5 angle and the trans will have a 5 angle which will give me a .5 degree delta between the front and rear spider angle, which is what I am shooting for. If the angles were opposite then they would be additive but judging by the lack of response to my OP, I am guessing this is something that few folks have thought about. As of now I haven't done anything but I am just following the instructions in the GearVendors shop manual at this point.
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anybody that`s changed a rear end for something else has surely thot about it. I just don`t understand ur terminology. u need a down ward relationship in the static position. when u drop the hammer on it it will kick up .
 
So when u say ur tranny was lowered because u installed the GVO did u take ur measurement off the end of the gvo. Do u mean it's actually 5 degrees down on the trans/ gvo. Then u need ur pinion 5.5 down if u want .5 difference. U always want the pinion lower than the trans/gvo. I would think u would need at least 1.5 difference. Hope this helps Kim
 
oldkimmer said:
So when u say ur tranny was lowered because u installed the GVO did u take ur measurement off the end of the gvo. Do u mean it's actually 5 degrees down on the trans/ gvo. Then u need ur pinion 5.5 down if u want .5 difference. U always want the pinion lower than the trans/gvo. I would think u would need at least 1.5 difference. Hope this helps Kim
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Kim: Following the GV manual I checked the front angle on the OD unit bottom pan. It read 5 degrees up toward the radiator. Then I checked the axle pinion angle using the GV manual instructions with a framing square off the rear cover bolt heads with the angle finder on the lower perpendicular of the framing square. It read 3 degrees up to the radiator as well. Per the GV book the 2 degree delta might have worked but they say ideal is within 1/2 degree. So I ordered some 1.5 degree pinion angel shims and installed them on the rear spring perches. Upon rechecking, the OD pan still read 5 degrees but the rear axle reading is now 4 1/2 degrees-should work. By your statement I need to go another degree change in the same direction to get the pinion lower than the GV angle. Thanks for the input, it is an easy change to make. I have test drove the car about 125 miles during testing and have verified the speedometer is within 1 MPH through the entire range and at 70 MPH my calculated RPM of 2400 is actually 2400 RPM with 3.73:1 ratio and 15" 275-60 tires on the rear. It appears I may have screwed the pooch by insisting on using PolyLoc motor mounts. May change back to stock rubber ones and tie the motor on the left side.
Thanks for your input, Douglas:)
 
DesertRat said:
Kim: Following the GV manual I checked the front angle on the OD unit bottom pan. It read 5 degrees up toward the radiator. Then I checked the axle pinion angle using the GV manual instructions with a framing square off the rear cover bolt heads with the angle finder on the lower perpendicular of the framing square. It read 3 degrees up to the radiator as well. Per the GV book the 2 degree delta might have worked but they say ideal is within 1/2 degree. So I ordered some 1.5 degree pinion angel shims and installed them on the rear spring perches. Upon rechecking, the OD pan still read 5 degrees but the rear axle reading is now 4 1/2 degrees-should work. By your statement I need to go another degree change in the same direction to get the pinion lower than the GV angle. Thanks for the input, it is an easy change to make. I have test drove the car about 125 miles during testing and have verified the speedometer is within 1 MPH through the entire range and at 70 MPH my calculated RPM of 2400 is actually 2400 RPM with 3.73:1 ratio and 15" 275-60 tires on the rear. It appears I may have screwed the pooch by insisting on using PolyLoc motor mounts. May change back to stock rubber ones and tie the motor on the left side.
Thanks for your input, Douglas:)
Click to expand...

The confusion I'm seeing in the responses to your posts stems from the up/down relationship of your angles. The standard way of naming the relationship of "up or down" is in relationship to the driveshaft. You called the engine trans angle up, but your transmission should be referred to as 5 degrees down angle and the pinion would be referred to 3 degrees upward angle , as you have correctly stated.

That being said, it sounds like now your pinion angle is .5 degree down in relation to the engine trans shaft centerline angle. Nice.

I too had the poly locks, and did not like the vibration transmitted to the car through them. I called Schumacher and ordered their torque shaft kit and a fresh set of stock rubber mounts, I like this much better, but beware. They will lower the front of the motor slightly as they are thinner than the poly's. It is likely enough of a difference to change the centerline relationship between the engine trans and rearend. Double check once you have swapped them in.
 
jbc426 said:
The confusion I'm seeing in the responses to your posts stems from the up/down relationship of your angles. The standard way of naming the relationship of "up or down" is in relationship to the driveshaft. You called the engine trans angle up, but your transmission should be referred to as 5 degrees down angle and the pinion would be referred to 3 degrees upward angle , as you have correctly stated.

That being said, it sounds like now your pinion angle is .5 degree down in relation to the engine trans shaft centerline angle. Nice.

I too had the poly locks, and did not like the vibration transmitted to the car through them. I called Schumacher and ordered their torque shaft kit and a fresh set of stock rubber mounts, I like this much better, but beware. They will lower the front of the motor slightly as they are thinner than the poly's. It is likely enough of a difference to change the centerline relationship between the engine trans and rearend. Double check once you have swapped them in.
Click to expand...
Thanks for the excellent advice. I have not decided to change the poly mounts but I am leaning that way. I have some stabilizing of the exhaust system to try before I let myself in for that headache. The car actually behaves pretty well-just getting some harmonics from the trunk area.
 
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