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Understanding pinion angle

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17K views 17 replies 10 participants last post by  TechGuy  
#1 ·
Didn't want to hijack a thread over in drag racing so am posting this here.

Please tell if I figured my pinion angle correctly. Car level with suspension loaded pinion nose is pointed down 4*. Driveshaft points down from tranny at 2*.
4*-2* = negative 2* down correct?
 
#2 ·
By some theories and explanations yes, and by some others the pinion angle is -4°

My understanding of pinion angle is how parallel it is to the tail shaft yoke. The only reason the drive shaft up or down angle comes into play is so it can be used as a reference point. Otherwise you would have to have the car 100% level which is impossible because where would you measure it for level? There is nowhere.

If you had the drive shaft pointing down from the tail shaft 2° that would be positive 2° then if the drive shaft was pointing up from the pinion 4° that would be negative 4°

So I do think you're right... -4° + +2° equals -2° or like you said -2° pinion angle.

Some people believe that the pinion angle is still -4° because that what it is to the drive shaft. Who's right, who's wrong, who knows anymore.
 
#3 ·
Forget about the driveshaft...pretend it's not even there. Measure your engine/trans angle and your rear end yoke angle. If your engine/trans is angled down 2* and your rear end yoke is pointing up 2*, you then have 0* pinion angle. If your rear end yoke is pointing level then you would have -2* pinion angle.

Refer to this guide...it explains everything. http://www.iedls.com/ptsetup.html
 
#4 ·
That guide is pretty vague. I still think it's important in a leaf sprung car to have the drive shaft installed to insure that the pinion is negative in relation to the drive shaft, or that the drive shaft points up to the transmission form the pinion. Under the torque hit the leaf springs wrap up bringing the drive shaft more in line reducing the drive shaft angularity instead of increasing it.

Without the drive shaft installed what reference would you use to see if the pinion is up or down? If the car was sitting on a down slope (let's face it, most of us work in our garages that aren't level at all) and you measure the pinion angle to be 2° pointed down. Well obviously level must have been used for a reference but what if your garage floor is sloped down 2° to the front of the car... not good. The pinion yoke is then really 0° and this isn't good in a leaf spring car. The same would hold true for the tail shaft or yoke, your reading would be skewed in the up direction 2°

Yeah, you can get the difference in the angles no matter what reference is used but I still say it's import to check them against the drive shaft. Because the transmission and pinion are rarely one the same planes it's easier with the drive shaft installed to see how close it is to being pointed straight into the pinion and the tail shaft yoke. Then you can make adjustments from there.

I guess the easiest way to see it in your mind is think about a severely lifted 4X4 where the transmission may be a couple feet higher than the pinion. Although it may be possible still get a good pinion angle it's impossible to get the drive shaft close to being straight into the tail shaft and into the pinion at the same time. The drive shaft angle is pretty extreme as are the U joints. It takes more power to turn U joints at an angle like that than if they were straight on. They can't tilt their transfer case/transmission/engine down enough to point at the pinion so they have to live with those severe angles and a little power robbing effect of the U joints.

In our drag cars or street/strip cars under the hit and full power we want the U joint angles to be as close to 0° as possible minimizing and any horsepower loss. On the street you need some angularity for happy U joints.

I suppose with the drive shaft angle to pinion and tail shaft it's just one of those things where you're going to see the importance or you're just never going to get it. It's hard to talk about pinion angle without talking about drive shaft angles.
 
#9 ·
ALLT4 said:
That guide is pretty vague.

it's easier with the drive shaft installed to see how close it is to being pointed straight into the pinion and the tail shaft yoke. Then you can make adjustments from there.
Click to expand...
Not sure why you say the Guide is vague...I've never seen anything explained in simpler terms & drawings. The drivshaft doesn't have to be pointed straight into the pinion and shouldn't be unless it's a race car. I don't pay any attention to whatever angle the driveshaft is...only the angle of the engine/trans and the rear end...the driveshaft is where ever it ends up after the two ends are connected.
 
#5 ·
I have read all these ideas that folks have come out with in the last 10 or 15 yrs and say they got it all figured out. I am old school and use the driveshaft and rear yoke angles like you did. I can tell you doing it that way and setting the angle nose down you will not break a U joint due to bad pinion angle. When I build a car from scratch I set the engine/trans to raer end angles and they work but Detroit set a street car up for all situations and all the theory guys can't fix what Detroit screwed up for a race car. JMO. RM
 
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#6 ·
if trans is pointing down -2* then diff should be pointing up +2* (must be within +/-2*) I like to set it 2* down from parallel. So if trans is pointing down -2* I set my pinion angle at 0*. If trans is pointing down -4* I set my pinion angle at +2* up. Hope this helps.

Miles
 
#7 ·
Aye !

I think what happens is some folks confuse pinion angle with u-joint angle.

Minimize u-joint angle for less power loss, set pinion angle to keep the pinion
& engine parallel under acceleration.
 
#8 ·
With my old set-up I paid no attention to the engine or driveshaft; the pinion was pretty much horizontal to the ground, and the car would not hook.
With 8 degree wedges in place it started lifting the front end, eventually running a best 60 ft. time of 1.34 on a 9" E.T. Street with slapper bars and mismatched junk shocks.
With my current Cal-Trac bars it wants at least 4 degrees (measured from driveshaft to pinion) With only 1-1/2 - 2 degrees it will spin, with 4 it's been almost on the bumper.
I haven't had a chance to test it with more angle, but it still does 60 fts. in the 1.3's with tires that are about 3 years old and pretty dried up.
 
#10 ·
I thought I explained that. Because the pinion and transmission tail shaft are rarely on the same plane it's kind of hard to tell how much U joint angle there will be without the drive shaft in place. I never said the drive shaft should pointed straight into the pinion and tranny. It should be CLOSE but but not straight on.

ALLT4 said:
it's easier with the drive shaft installed to see how close it is to being pointed straight into the pinion and the tail shaft yoke.
Click to expand...
Does that say anywhere it should be straight on?

IMHO the pinion should always be pointed down in relation to the drive shaft, when the torque hits it brings the drive shaft closer to straight on. If the pinion is pointed up in relation to the drive shaft the U joint angles can only get worse with torque applied no matter whether the tail shaft is up or down.

Probably doesn't make a hill of beans difference in a 4 link but on a leaf spring car it's way important to have the drive shaft pointed up to the tranny instead of down to it. Like I said, you're either going to see it in your mind or your not.

U joints are suppose to have some angle to them but not excessive. If you don't want to pay any attention to those angles so be it. But to suggest they aren't important is misleading.

That's the part of the article I'm talking about that they don't make real clear.
 
#15 · (Edited)
ALLT4 said:
Because the pinion and transmission tail shaft are rarely on the same plane it's kind of hard to tell how much U joint angle there will be without the drive shaft in place.

If you don't want to pay any attention to those angles so be it. But to suggest they aren't important is misleading.

That's the part of the article I'm talking about that they don't make real clear.
Click to expand...
The driveshaft doesn't have to be in place to determine how much U joint angle there will be. Pinion angle is the difference between the engine/trans angle and the rear end angle. Generally -2* to -3* is a good number. Yes, you do have to pay attention to the angle, I didn't say it wasn't important. As long as you maintain the 2* to 3* or less difference there's no way the U joint angle can be any issue. Again, you don't need a driveshaft in place to figure it out or measure it, only the difference between those two angles.

Your engine/trans could be pointing down 10*...as long as your rear end is pointing up 7*-12* that gives you a 6 degree range minus 3 to plus 2 that should work just peachy. When I setup pinion angle, I put the digital level on the engine and the pinion yoke, that's it.
 
#11 ·
I've set my pinion angle in relation to the driveline angle. Drive line can be measured at the tailshaft or oil pan rail. You want the differential yoke to be 1 - 2 degrees down from the driveline. If the driveline is down 3 degrees, the yoke should be up 1 degree. High horsepower drag cars can use a little more down angle on the yoke.

If you have a 3rd gen big block car or Chrysler, you will set the pinion angle level (if driveline down 2 degrees then yoke up 2 degrees) to the drivetrain. These cars shift the engine to the right and achieve the necessary u-joint needle bearing rotation by the left to right shift.
 
#13 ·
Wow!!

With the driveline loaded you want the operating angle of the front and rear U-joints to be as close to equal as possible.... When this is the case the oscilations caused by the u-joints operating at an angle will cancel each other out. For that to make sense you have to understand the operation of a u-joint when it's at an angle, there's is an elipticle(however you spell it) rotation. Meaning there is not a constant velocity and the amount of variation depends on the angle it's operating at. While a 0 degree angle seems best the problem is the needle bearings will not turn at all and will get crushed eventually so a slight angle is desired.

Now it's tricky to figure out how much the axle rotates on a leaf spring car so thats where it gets tricky!! And the relation of the angle of the pinion to the ground has nothing to do with how the car will hook, it depends on it's relationship to the rest of the driveline.
 
#14 ·
8 people have replied and it looks to me like there are several different ideas expressed. As I said there isn't alot of agreement on this subject. Best of luck. :turn: RM
 
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#18 ·
what you are showing is u-joint angles, which you are correct.. they should
minimized. & they must be checked with the drive line in place, car at ride height.

the pinion angle is based off the crank shaft centerline.
 
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