68383GTS
Well-Known Member
Narrowing a rear end and welding on spring perches. What should the pinion angle be at?
Pinion angle
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mopar head
Well-Known Member
Put them the same as old rear if ride height has`nt changed.
Garry in AZ
Building a 9 second Valiant
Normally with leaf spring cars you should aim for about 3-5 degrees of negative angle. The opposite angle of the same value should be found at the output of the transmission.
Pinion angle should be the same as the transmission angle, but in the opposite direction.
Treblig
Well-Known Member
I dont know why that gets thrown around. The spec is static. Read the Mopar Suspension manual. It's all there.
Treblig
Well-Known Member
From everything I've read the pinion will rise (pinion U joint) under acceleration at which time it will no longer be parallel. It's supposed to be parallel to minimize vibrations under a load?? You'll never get a vibration sitting still.
Treblig
Sure it does, but how long will you remain in hard acceleration? Or will you be longer at just cruise?
If you read the book, it's all in there. For performance, sure you want the pinion further down.This is where the "5-7* nose down" comes from. But for everyday street driving, it should be even, or very close.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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It's best IMO, to leave them loose and lightly bolted in. Then set your ride height.; front and rear. Then set you angle. And you need to compensate a bit extra for soft street springs, and hi-torque engines, and racing versus street.
To get an idea of how much to compensate, just watch the pinion jump, up on any rear wheel drive car, from no load applied to when the operator locks the brakes,and puts it in gear, and gives it a bit of gas. With street springs it moves around quite a bit ; maybe 4/5* just on that, and you haven't even really put much power into it. If you don't compensate enough, the pinion will go nose up, and then it will really vibrate. I over-compensated and had to install some shims. No big deal.
Some books say 5 to 7, my bulletin book says 5 to 10,some say equal but opposite to the front, when loaded. Really it's almost a crapshoot.
I went 7* down, and later took 2* out because I was not enjoying the steady-state at 65=2200. It got a bit better. My thought was that at 7* I was safe to add or subtract a 2* shim, and it worked out great.
To get an idea of how much to compensate, just watch the pinion jump, up on any rear wheel drive car, from no load applied to when the operator locks the brakes,and puts it in gear, and gives it a bit of gas. With street springs it moves around quite a bit ; maybe 4/5* just on that, and you haven't even really put much power into it. If you don't compensate enough, the pinion will go nose up, and then it will really vibrate. I over-compensated and had to install some shims. No big deal.
Some books say 5 to 7, my bulletin book says 5 to 10,some say equal but opposite to the front, when loaded. Really it's almost a crapshoot.
I went 7* down, and later took 2* out because I was not enjoying the steady-state at 65=2200. It got a bit better. My thought was that at 7* I was safe to add or subtract a 2* shim, and it worked out great.
68383GTS
Well-Known Member
l will have to check but I think my new springs are ss springs.
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I think that's how I would do it, yes.
Sorry for the high jack. When mentioned of 5*-7* down. Is it from the drive shaft angle or trans angle? Here's my situation. My Trans is slanted 2* down. I messed up and welded my perches with the pinion leveled out, with perches 5* down. I probably should have welded my perches so the pinion faced up 2* right? that would have phased the pinion angle with the transmission angle. So by my beer math I am negative 7* from transmission angle? I'm going to wait until I get my springs installed and see what it looks like under my car. But I will admit i messed it up and most likely be cutting them off and redoing it. It's just a street cruzer.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The pinion must be nose-down from the driveshaft. The driveshaft is the reference.
In this way, when you put the power into it, the pinion will rise up towards zero. The idea is that at max power, the pinion angle will be between; equal and opposite from the trans angle , and zero.
The more power you have, the higher the pinion will climb. Likewise if your springs are soft, and they wrap up at the front. Likewise if your suspension hooks.
In a streeter it is often better to bias the angle to the small end of the range for smoothness when cruising. Cuz most of the time she'll be spinning anyway.
In a racecar it is best to bias closer to zero angle at full power.
In this way, when you put the power into it, the pinion will rise up towards zero. The idea is that at max power, the pinion angle will be between; equal and opposite from the trans angle , and zero.
The more power you have, the higher the pinion will climb. Likewise if your springs are soft, and they wrap up at the front. Likewise if your suspension hooks.
In a streeter it is often better to bias the angle to the small end of the range for smoothness when cruising. Cuz most of the time she'll be spinning anyway.
In a racecar it is best to bias closer to zero angle at full power.
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On a factory 8.75 A body rear, the perches set pinion at up 5*.
When installing them myself, I never use the factory setting. I usually weld them on anywhere from 0 to 2* up depending on application.
On a street driver, you usually don't want more than 3* down compared to tailshaft when installed in the car. Driveshaft has nothing to do with it the way I go about it.
When installing them myself, I never use the factory setting. I usually weld them on anywhere from 0 to 2* up depending on application.
On a street driver, you usually don't want more than 3* down compared to tailshaft when installed in the car. Driveshaft has nothing to do with it the way I go about it.
famous bob
mopar misfit
I `ve got mine 2-3 degrees down. Always have and always will. Levels out on acceleration. Never a problem.
if your trans is 2 deg down.rear pinion shoud be set at 1 deg down,that way under drive conditions the rear pinion will rise up 2-3 deg.making them parallel (sp)
If that is the case do you guys suggest I cut the perches off or do you think a 4* shim would work. Its possible the shim may be to large and not allow for the locating pin to seat on perches. This is just for planning purposes as I still need to order my new 6 Leaf +1 EPSO's and see how the -5* looks before I make any changes but chances are I will need the shims or re-weld some new perches.
Treblig
Well-Known Member
A 4 degree shim is totally acceptable.....I always buy the type of shim that has a hole for the spring center bolt that way I know for sure tat it won't move or slide out but sometimes it means that you have to buy a longer spring bolt??? The pin for the perch should still be there for alignment.
treblig
mischiefdart
Well-Known Member
How about if you are running caltracs? I am doing a Dana 60 for my 70 Dart and still have to weld the perches on.
Everyone seems to have their own story about pinion angle so I'll add mine. On my Chevy S10 race truck (circle track) the trans output shaft was 2 degrees up. I set the pinion at 2 degrees down sitting at ride height with no load. Never had an issue under race conditions where I was turning the engine at a steady 5000 - 7500 RPMs every lap.
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