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Pinion Angle - One More Time - Please
#1187761
02/28/12 10:07 PM
02/28/12 10:07 PM
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Joined: Jan 2003
Posts: 5,186
Wherever I am.
Junky
OP
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OP
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Joined: Jan 2003
Posts: 5,186
Wherever I am.
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OK, I raised the Coronet up on a 4 post hoist. Jacked the front end up so the drive line is level at 0°. The transmission slip yoke is 2.5° down (negative). If I understand correctly the pinion should be parallel to the slip yoke. The thing is the rear end is higher than the transmission. So the only way to make the pinion parallel is to have it 2.5° up (positive). Let me ask, simply. With the drive line level at zero degrees, trans down 2.5°, what should the pinion be at...keeping in mind the rear end is higher than the transmission? Down or up? I didn't think that the pinion should be positive. I have Schumacher engine and transmission mounts. There's no way to raise the transmission. No room. And if I raise the rear of the car it will look like a stink bug. 
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Re: Pinion Angle - One More Time - Please
[Re: bobs66440]
#1187764
02/29/12 12:11 AM
02/29/12 12:11 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Bob you want them parallel then the pinion 2-2.5 deg down from that point on a normal rubber suspension?
live every 24 hour block of time like it's your last day on earth
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Re: Pinion Angle - One More Time - Please
[Re: bobs66440]
#1187766
02/29/12 02:04 AM
02/29/12 02:04 AM
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Joined: Aug 2003
Posts: 12,291
Kent, Wa
340SHORTY
Truck Nut
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Truck Nut
Joined: Aug 2003
Posts: 12,291
Kent, Wa
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I always heard the the pinion should be 2 to 4 degrees down fron the tail shaft. that way under acceleration the rear axle rotates up and becomes even with the tail shaft.
I am truckless..
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Re: Pinion Angle - One More Time - Please
[Re: bobs66440]
#1187767
02/29/12 02:10 AM
02/29/12 02:10 AM
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Joined: Jan 2003
Posts: 5,186
Wherever I am.
Junky
OP
master
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OP
master
Joined: Jan 2003
Posts: 5,186
Wherever I am.
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Something came to mind. Transmission down 2.5°, pinion up 2.5°: on acceleration, won't the rear end want to climb (rotate) up more than 2.5°? And while driving, with the rear wheels propelling the car forward won't the pinion be up more than 2.5°? Will that cause a problem? Or am I over thinking this?
Edit: 340Shorty said what I've heard too. That's why I was wondering...
Last edited by Junky; 02/29/12 02:12 AM.
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Re: Pinion Angle - One More Time - Please
[Re: Junky]
#1187769
02/29/12 07:52 AM
02/29/12 07:52 AM
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Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
bobs66440
top fuel
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top fuel
Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
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Quote:
Something came to mind. Transmission down 2.5°, pinion up 2.5°: on acceleration, won't the rear end want to climb (rotate) up more than 2.5°? And while driving, with the rear wheels propelling the car forward won't the pinion be up more than 2.5°? Will that cause a problem? Or am I over thinking this?
Edit: 340Shorty said what I've heard too. That's why I was wondering...
Under hard acceleration the pinion will want to climb the ring gear initially, yes but the rear is secured to the springs which will resist the action. As mentioned, under braking it's just the opposite. Under normal driving the rear will naturally pivot a little but the fact that it's bolted to the springs holds it true for the most part. Because the axle will naturally go up and down, the angles will always be changing slightly, but the initial setup is a good compromise. With leaf spring rears, traction bars are used to keep the springs from wrapping up due to the ring gear climbing which also helps to keep the pinion angle in check. For high horsepower drag cars that spend all of their meaningful time under hard acceleration, the setup will be different. The idea for a street car is to have the optimum angles for the most time as possible. With a four link, ladder bar setup or similar it's not an issue because the rear is held fast to a certain angle by the radius rods/ladder bar. In that case the pinion angle only changes when the whole axle assembly pivots up and down on the front rod mounting points, but the change is minimal in most cases.
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Re: Pinion Angle - One More Time - Please
[Re: RapidRobert]
#1187771
02/29/12 12:20 PM
02/29/12 12:20 PM
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Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
bobs66440
top fuel
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top fuel
Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
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Quote:
Quote:
As long as the pinion and output shaft centerlines are parallel and there's approx 2-3 degree angle in relation to the driveshaft, it's good.
Oh OK you want the centerlines parallel but not in the same plane like the pic AND AT THAT POINT the pinion 2-3 deg downward from the DRIVESHAFT. Cause the pinion will rise up making the pinion & the driveshaft closer to a straight line?
Right, when the car is on the ground and sitting with weight on the suspension, you want the rear and trans parallel but NOT on the same plane (in line) with each other. The 2-3 degree angle is in relation to the drive shaft only not to the ground. As the suspension goes up and down in normal driving, the angle will naturally change a little to the positive and negative to that angle. Most production cars have the engine in the car at a 2-3 degree angle (tail down) in relation to the level plane of the car (and ground). That's why intake manifolds are higher in the back than the front...to level the carb. Then the rear is angled 3 degrees UP to match the engine angle. In theory, the drive shaft (if installed level) will have a 3 degree angle in relation to the rear and trans on each end.
The upper right diagram is described as for tube chassis drag cars only. That will produce the least resistance. Some drag racers with leaf springs will set it up so the rear is angled down relative to the trans, so that under acceleration when the pinion climbs the ring gear, it will then have the correct agle. Then at the end of the race it will revert back to the non-aligned angle. But you wouldn't want that for the street. You will get a lot of vibration and there will be a lot of stress on the u-joints.
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Re: Pinion Angle - One More Time - Please
[Re: bobs66440]
#1187772
02/29/12 01:28 PM
02/29/12 01:28 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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got it  thank you Bob
live every 24 hour block of time like it's your last day on earth
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Re: Pinion Angle - One More Time - Please
[Re: Junky]
#1187775
02/29/12 07:21 PM
02/29/12 07:21 PM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
top fuel
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Posts: 1,688
Marlboro, NY, USA
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Quote:
OK, I raised the Coronet up on a 4 post hoist. <snip...>
NO. The car must be supported by the suspension (rear at least) or the measurements are meaningless.
I've always liked the factory direct-reading tool which doesn't "care" if the car is level or not (but paragraph above still applies).
Drag cars with leaf springs an no other windup control typically need pinion down 3-4° (in relation to the propshaft).
True street cars will be much happier with 1° or so.
Front angle should be a very small amount "shaft down", but not zero (some movement prevents grease from becoming rock hard!)
Rick
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Re: Pinion Angle - One More Time - Please
[Re: Junky]
#1187777
02/29/12 10:07 PM
02/29/12 10:07 PM
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Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
bobs66440
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top fuel
Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
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When they say pinion "nose down", it means in relation to the drive shaft. If the trans is higher than the axle, then the pinion will be "nose down" in relation to the axle, but the trans and pinion should still be parallel (see diagram). With your car set up with the suspension loaded as you have (on your 4 post lift is ok) use an angle finder to get the angle of the centerline of the output shaft on the trans. Then use the angle finder on the pinion of the rear and match that angle, but make it OPPOSITE on the same plane as in the diagram. Now, if you attach the drive shaft and measure the difference in the angle between the driveshaft and the pinion or trans, it should be 2-3 degrees. Some people say as little as 1 degree and as much as 7 degrees is ok. I believe most u-joints have a max working angle of 3.5 degrees and min of .5 degrees, so I would keep it in that range. Here's a good tutorial explaining the whole thing. Sometimes I don't explain things very well, but if you follow this, you will be fine. http://www.hurst-drivelines.com/files/Universal_Joint_Alignment_Proc_111606.pdfAs stated in above posts, there are many theories and one (for drag cars) is to have the pinion 1 or 2 degrees lower than what's described above so that when the pinion climbs the ring gear it will then be lined up properly.
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Re: Pinion Angle - One More Time - Please
[Re: 383man]
#1187778
03/01/12 03:25 AM
03/01/12 03:25 AM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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Quote:
Quote:
Something came to mind. Transmission down 2.5°, pinion up 2.5°: on acceleration, won't the rear end want to climb (rotate) up more than 2.5°? And while driving, with the rear wheels propelling the car forward won't the pinion be up more than 2.5°? Will that cause a problem? Or am I over thinking this?
Edit: 340Shorty said what I've heard too. That's why I was wondering...
That is wrong with the trans down 2.5 and the pinion up 2.5. That would be 0 pinion angle. You want a difference of 2 to 3 degrees down so when the pinion wants to go upward on acceleration it goes closer to 0 but not 0 as you want some angle so the U-joints will work and move the lube around in them. If you had a trans say 2 down you would want the pinnion 4 or 5 down for 2 to 3 down pinion angle. Ron
I am sorry as I was wrong here. I was thinking the trans was the driveshaft angle and thats why I said it was wrong. I thought it was saying the driveshaft and the pinion were both 2.5 when they ment the trans was 2.5 and the pinion also 2.5 which is correct. Then you would have to measure the driveshaft angle to see what that is. If the driveshaft measures 4.5 up then the pinion angle would be 2. Ron
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Re: Pinion Angle - One More Time - Please
[Re: 383man]
#1187779
03/01/12 06:06 AM
03/01/12 06:06 AM
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Joined: Dec 2007
Posts: 18,157
Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,157
Mass
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Re: Pinion Angle - One More Time - Please
[Re: Rick_Ehrenberg]
#1187780
03/01/12 06:12 AM
03/01/12 06:12 AM
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Joined: Dec 2007
Posts: 18,157
Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,157
Mass
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Quote:
Quote:
OK, I raised the Coronet up on a 4 post hoist. <snip...>
NO. The car must be supported by the suspension (rear at least) or the measurements are meaningless.
I've always liked the factory direct-reading tool which doesn't "care" if the car is level or not
Rick
A 4 post lift is a "drive on" ramp style lift, the suspension is compressed.......
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