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Old 05-20-2020, 07:32 PM
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Default Pinion angle

Can someone tell me the proper way to go about this . The car is a 1964 Lemans with a Moser 9" rear. Im getting all different ways on how to do it when i look it up. One way was to measure the trans angle and shaft angle and subtract them. Same with the rear side . Then add up the two and that will be the pinion angle. When i do it this way im coming up with 7degree's. What is the best angle ? Is something like 2 degree's good?

Thanks

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Old 05-20-2020, 07:50 PM
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How specifically did you arrive at the 7 degree number? The answer to how much can be different. The old Southside bars recommended ~5 due to the movement they caused, and for the angle to be close to inline under power. I think mine's at 2.5 negative, static right now with stock location points.
Also do some checking on your location points and you can use some of online calculators to figure instant center and antisquat if you haven't already.

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Last edited by Scott65; 05-20-2020 at 08:07 PM. Reason: Clarification
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Old 05-20-2020, 08:55 PM
73 TRANSAM 73 TRANSAM is offline
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Charlie,
This is how I did mine. They don't even care about the driveshaft to determine the angles. You need to measure the balancer or trans output housing. Most will get -3 to -4 on the trans pointing down. Then you measure your pinion yoke, most likely it will be pointing down too, so its -4. Then if you add them together, it will be-7 or -8. The thing is, when you accelerate at the starting line, your pinion goes up. So in this case you want the maximum pinion angle to go +3 to +4 to get a perfect alignment. This is why a ladder bar works so good at controlling the pinion. On a street car suspension, you just make sure your pinion is pointing down. On the start up, you are hoping you compensated enough so that the pinion is not going past +3to +4 (up too much). When it goes over that number is where the U joint breaks. The less the angle, the less horsepower it robs and it is smoother on the higher rpm. You know my number.

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Old 05-20-2020, 09:42 PM
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Quote:
Originally Posted by Scott65 View Post
How specifically did you arrive at the 7 degree number? The answer to how much can be different. The old Southside bars recommended ~5 due to the movement they caused, and for the angle to be close to inline under power. I think mine's at 2.5 negative, static right now with stock location points.
Also do some checking on your location points and you can use some of online calculators to figure instant center and antisquat if you haven't already.
I rounded it off to 7 actually. I came up with 6.66 The way i did it was: trans yoke was 3.30 going down towards the rear and drive shaft yoke was .70 going down towards the rear. I subtracted .70 from 3.30 = 3.23 . did the same at the rear yoke and shaft yoke. Shaft was .70 . Rear end yoke was 3.43 going down towards the trans. added 3.23 to 3.43 = 6.66 degrees? lol

I read this and tried it. I have no idea if its right..

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Old 05-20-2020, 09:42 PM
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Quote:
Originally Posted by Scott65 View Post
How specifically did you arrive at the 7 degree number? The answer to how much can be different. The old Southside bars recommended ~5 due to the movement they caused, and for the angle to be close to inline under power. I think mine's at 2.5 negative, static right now with stock location points.
Also do some checking on your location points and you can use some of online calculators to figure instant center and antisquat if you haven't already.
Ok Ed . Ill give you a call...

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Old 05-20-2020, 09:50 PM
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Quote:
Originally Posted by Scott65 View Post
How specifically did you arrive at the 7 degree number? The answer to how much can be different. The old Southside bars recommended ~5 due to the movement they caused, and for the angle to be close to inline under power. I think mine's at 2.5 negative, static right now with stock location points.
Also do some checking on your location points and you can use some of online calculators to figure instant center and antisquat if you haven't already.
I bought some UMI lower control arm brackets to lower the the arms down at the axle tube. So im working on getting the IC in the ballpark. They told me before i start welding them in , i have to make sure the pinion angle is right. So im starting with getting the angle right first . Right now as it sits the lower arms are parallel to the ground. Im trying to get some angle on them ..

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Old 05-20-2020, 09:52 PM
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Quote:
Originally Posted by 73 TRANSAM View Post
Charlie,
This is how I did mine. They don't even care about the driveshaft to determine the angles. You need to measure the balancer or trans output housing. Most will get -3 to -4 on the trans pointing down. Then you measure your pinion yoke, most likely it will be pointing down too, so its -4. Then if you add them together, it will be-7 or -8. The thing is, when you accelerate at the starting line, your pinion goes up. So in this case you want the maximum pinion angle to go +3 to +4 to get a perfect alignment. This is why a ladder bar works so good at controlling the pinion. On a street car suspension, you just make sure your pinion is pointing down. On the start up, you are hoping you compensated enough so that the pinion is not going past +3to +4 (up too much). When it goes over that number is where the U joint breaks. The less the angle, the less horsepower it robs and it is smoother on the higher rpm. You know my number.
Thanks Ed ill call you..

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Old 05-20-2020, 10:21 PM
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If I'm understanding your numbers correctly, I'd call that 2.7 negative, and if you have adjustable uppers, a good starting point. Especially if the bars your talking about are "lift bars". I think by most accounts your engine power is on the high side to be using those if that's what they are. Do the instant center and antisquat calculations before you decide they "need" some angle.

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Old 05-21-2020, 02:13 AM
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All you are shooting for is parallel under load. So the less compliant the suspension joints are the closer to the same they will be . The actual driveshaft angle has no bearing on it. The rear and trans need to be parallel under load. So if you see -3 at the crank or tail housing you should shoot for positive 3 at the rear end if there was no compliance in the suspension. But there is always some movement so in practice you would see -3 at crank and 0 to 2 positive at the rear to account for suspension movement. All for no vibration and the easiest power transfer. There is a wide range of right just more vibration some ways than others. If you google it there is a very good video from a driveline company but I can't link it

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Old 05-21-2020, 07:02 AM
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Tremec has an app (search pinion angle) for your iPhone (not sure about other brands). Simple and easy and uses your iPhone as the measuring device. It got me in the ballpark and I went from there.

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Old 05-21-2020, 07:16 AM
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Quote:
Originally Posted by rod cole View Post
All you are shooting for is parallel under load. So the less compliant the suspension joints are the closer to the same they will be . The actual driveshaft angle has no bearing on it. The rear and trans need to be parallel under load. So if you see -3 at the crank or tail housing you should shoot for positive 3 at the rear end if there was no compliance in the suspension. But there is always some movement so in practice you would see -3 at crank and 0 to 2 positive at the rear to account for suspension movement. All for no vibration and the easiest power transfer. There is a wide range of right just more vibration some ways than others. If you google it there is a very good video from a driveline company but I can't link it
This is correct. Set your rear pinion at 0° if you think there will be 3° of upward movement of your pinion under load. Set the pinion at +1° if you expect 2° upward movement etc.

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Old 05-21-2020, 08:55 AM
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Scott, So how are you coming up with 2.7? I was under the impression that if you have two negative numbers you have to add them together.. As for the power , its 650rwhp and shooting for 700.

rod cole , When you say positive at the rear will the yoke be pointing up or down towards to front of the car? If you can think of that link posted if you dont mind. Id like to check it out.

Dan, I tried that phone APP and it confused me lol. I didnt know what side of the car to try it from. The arrow for up and down was different from pass side of car to drivers side when i tried it from both sides. Which side should i do it from? I came up with 2 different out comes..

AG, is +1 up towards the floor ? One thing is the way the car is now at a 2500 rpm cruise the rear veiw mirror is blurry from vibration . So with the trans at 3.30 down and the rear 3.50 down . Both going down towards eachother. What would you say the pinion angle is?

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Old 05-21-2020, 09:40 AM
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+1 is towards the floor. If the trans is down and the yoke is down then it would be -6.8°. If the trans was down 3.5° and the yoke was up 3.5°, your pinion angle would be 0°.

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Old 05-21-2020, 11:12 AM
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Charlie, If the engine and trans are on factory mounting locations, I only worry about the angle between the drive shaft and pinion yoke. Get it between 1 and 3 pinion down in front in relation to the drive shaft. There's lots of complicated ways, and maybe they're necessary if your building a chassis, with custom motor and trans mounts. Ive never had drive line vibrations the way i do it. FWIW... At your power level study anti squat recommendations for the tire type you plan to run to help you with deciding on initial bar angles.

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Old 05-21-2020, 03:05 PM
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Easiest way is to draw two lines on the paper one with the engine pointing down the other with rear pointing up so both lines are parallel to one another under load.So
if the engine is -3 which most gm's are, the rear needs to be +3 to be at zero pinion angle, then u adjust from there to compensate for the amount of pinion wrap up,
obviously leaf spring cars need more, then a 4 link or ladder bar car. If leafs, put the rear at -2 that would be 5 degrees of pinion angle

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Old 05-21-2020, 03:18 PM
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The yoke will point up to compensate for the trans pointing down depending on the movement in the rearend attaching points Like was stated a line through the pinion and a line trough the crank will be parallel but in different planes. The driveshaft angle is just what it is no right or wrong on it as long as the relationship between the engine and rear are parallel under load.

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Old 05-21-2020, 08:15 PM
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So i adjusted the uppers until i got zero on on the rear yoke . Now the rear veiw mirror really vibrates when cruising. Its seems that by raising the rear it made things worse up front. So tomorrow im going to raise the tail of the trans. I got 3.85 down on the trans and 1.40 on the drive shaft. It looks bound up, with the top of the u joint space alot smaller then at the bottom .

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Old 05-21-2020, 09:36 PM
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If it were mine at 3,89 down on trans I would start at 2 dgrees up at the rear end pointing up . again the driveshaft angle is whatever it ends up at once you acheive parallel. .My car the rear yoke is considerable higher than trans so the angle on the shaft is wonky but runs smooth to 125 mph

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Old 05-21-2020, 09:38 PM
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video https://www.youtube.com/watch?v=gmV4qwLfOMY

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Old 05-22-2020, 06:05 AM
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That is an excellent video!



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