Drag Racing Tech - Pinion Angle ??

I have a UMI body mount TA and I was wondering what I should set the PA at. In the instructions it says to set it at 0 degrees. The car has a TH-400 with drag shocks and all tubular suspension. Also what would be the best way to set it, I bought an angle finder from Home Depot to use.

Set the car at ride height. Set your angle finder on the pinion yoke and set the pinion 2 degrees down.

The car is at ride height right now. So do I leave the angle finder on the drive shaft then move the TA until the angle finder reads -2?

I did a search when i put mine in and found too many different ways to set it. The way i did mine was i put the angle finder on the face of my crank pully to see the angle og my motor. Then put the angle finder on the bottom part of the TA (big flat piece the bolts go trough) and find that angle. Then find the differance of the 2 and thats your pinion angle. I got mine aet at -2deg. Best part of that set up is the car doesnt need to be level because no matter where your car is at, the 2 mounted parts on the car will always be the same.

Pinion angle is a reference from the pinion to the ground. The driveshaft and crank shaft is irrelevant to pinion angle. The only time the driveshaft comes into play is "driveline" angle.

well thats where too much info comes into factor. Hummm... can you explain a little more? Im under the asumption that you want your driveshaft at 0 deg. when WOT.

You are correct the pinion is going to try to roll up and be parallel to the track. This will cause the load to be placed on the suspension and lift the car and plant the rearend. The driveshaft etc is irrelevant because it can be mounted higher or lower than the pinion .

Guys, just listen to MadMan. He is the "Man" when it comes to suspension and putting a car on its rear bumper. He knows his shit!!!! :cheers:

David

So how do I need to go about setting the angle?

Set the car at ride height. Set your angle finder on the pinion yoke and set the pinion 2 degrees down.

Madman , shouldn't you zero the angle finder? Where is the "zero" or neutral point? Here is what I am after...if the Tq Arm was put in with "X" degrees down up or doesn't matter really...how do you get the rear to Parallel then go 2* neg or down?


I was gonna ask you this yesterday and it slipped my mind.

David

The adjuster on the torque arm sets pinion angle. Moving the arm up or down changes instant center. The pinion is your 90 degree off the ground so if you set the pinion to 88 degrees down then you are at 2 degrees.

So MADMAN, i set my pinion -2 deg. so under WOT my pinion is gonna be parallel to the ground? If so i get that point. Now on my specific car i have poly motor/trans mounts. In turn raised up my motor/trans a tad. So what if that makes my driveline angle in a bind? Wouldnt i start tearing up my u-joints?

I havent seen a drag car get in a bind from poly mounts. Also if your suspension is stiff enough the pinion will never get to zero.

Put 28" tires on the back, 24's on the front, instant -2 PA. lol

thats what i got now, lol. So then i guess im crawlin back under there and gettin it set up again, thanks madman!! lol. Any other words of wisdom??

Wolfe has some good diagrams for reference. see www.wolferacecraft.com/pinionangle.aspx

so madman, when you set the pinion -2* from the ground why/what does that do to the suspension. Im gonna take a wack at it and say it plants the tires good but how/why? Im gonna set it up that way but wanna know why for personial referance. thanks man!

When the power comes on the rear end tries to do a backflip.
By setting your PA negative you are counter acting the twisting motion.

The adjuster on the torque arm sets pinion angle. Moving the arm up or down changes instant center. The pinion is your 90 degree off the ground so if you set the pinion to 88 degrees down then you are at 2 degrees.
Which hole would be good to start out on with the instant center? With a Madman T/A. Street Vs. Track?

Which hole would be good to start out on with the instant center? With a Madman T/A. Street Vs. Track?

I start in the center hole and measure the angle of the bottom bar on the arm. You want it to run slightly down hill

Pinion angle is a reference from the pinion to the ground.


Only true if your motor/transmission is level with the ground at ride height (which it probably is not).

Only true if your motor/transmission is level with the ground at ride height (which it probably is not).

So in your theory how would you set pinion angle is your crankshaft and tailshaft is 10" off the ground and the pinion is 14 1/2 from the ground which would have the driveshaft running uphill to the pinion?

So in your theory how would you set pinion angle is your crankshaft and tailshaft is 10" off the ground and the pinion is 14 1/2 from the ground which would have the driveshaft running uphill to the pinion?

Why would you care how far the tailshaft or the pinion is off the ground? I would suggest that the frame rails are a better reference point. As I said before, If your motor is level to the ground your method works (assuming that it is level with the frame rails). According to what you have posted, I would have to adjust my pinion angle if I change the front tire diameter. That just isn't true. Pinion angle should only need to be changed if the relationship of the transmission to the rear is changed (shorter rear springs, etc.).

Right.

If your transmission output shaft is not paralell with the pinion and the ground, then a -2* pinoin angle (in reference toward the ground) could in reality be perhaps -5* or more.

Home depot has some great leveling tools you can use to get the angle offset between your pinion and your transmission output shaft. If you want to use the floor as your reference point, you could do a little math to come up with the correct angle.

Here is an extreme example just for refence purposes only..

Say you have a chassis with no engine/trans, but a full tank of gas. The front will sit higher than the back. There will be a downard angle from front to back, trans output shaft to rear end pinoin. Lets say, to keep it simple that angle is 5 degrees.

Now, if you were to setup your pinion angle now, in reference to the ground at a -2* angle, you add the angle from your trans output shaft to your pinion, and you would be left with a -7* angle at the pinion.

This is because pinion angle is a measurement of difference in paralells between the pinion output line and the driveshaft line. Since the driveshaft is connecting to the trans output shaft, you really should use that as your reference, unless like GIZMO said, they are at the same height in reference to the ground.

Now, this example is an extreme case, but its just to show that you should use the trans output shaft as your reference point.

Wolfe has some good info.

Note the caption on one of their images:
"Note that the pinion is 1 degree down but the pinion angle is 4 degrees down. It is the difference between the pinion and the driveshaft that matters."

goign by madman's method, you can probably just stick the guage on the bottom of the rear casing (providing it's a parallel surface to the pinion gear) and adjust by that, with someone sitting in the car so that it is at proper ride height.... is that correct?

Yes, as long as your trans output shaft is the same distance off of the ground as your pinion. Then you'd be set.

You guys are making this way too hard. This argument has been going on for years and the chassis builders never agree. Just like your computer tuners. Everyone is trying to get the best out of the car. My way works for me and my customers and the 60ft times and ETs show it. I have tried it the other ways and after 1000s of passes on different cars this the best way for me.

Madman am I correct in assuming that the bottom of a 12 bolt case shoudl be parallell with the rear pinion angle? Only reason I ask is it would make slugging the guage on and checking the angle really easy.

It should be parallel JL

cool, then slugging someone in the drivers seat and putting the guage on the bottom of the housing will let me check where it's at, and adjust accordingly. Thanks!

This is what I do; Stick the angle finder on the bottom of the torque arm and adjust it from there. I have mine set at -3 and it works great for my car.

bottom of the rear cover, bottom of the tq arm mount, same thing really.

You guys are making this way too hard. This argument has been going on for years and the chassis builders never agree. Just like your computer tuners. Everyone is trying to get the best out of the car. My way works for me and my customers and the 60ft times and ETs show it. I have tried it the other ways and after 1000s of passes on different cars this the best way for me.

Just one question. If you change the front tires from a 26" to a 27.5" would you re-check the pinion angle and adjust accordingly?

I would

I would

Please explain why.

I would if it changed ride height. . I would also realign the front end because of the caster change.

changing the angle of the chassis will change the pinion angle. The ride height thing/realign I hadn't thought of.... but madman's right it's probably a good idea.

Changing the front tire height does not adjust the pinion angle, however it WILL adjust the angle between the pinion and the ground parallels.

Its really easy to measure pinion angle, especially if you have the driveshaft installed.

Throw your angle meter on the driveshaft and measure it, then throw it on your pinion, now subtract the difference and now you have your true pinion angle. And you're done. :)

changing the angle of the chassis will change the pinion angle.
Changing the angle of the chassis does not adjust the pinion angle as the pinion angle is basically, in direct relation to the chassis (not the ground). Thus, no matter what your ride angle may be, your pinion angle will be constant.

This is, until you start transfering weight. At that point your pinion angle does change as your transmission output will remain fixed in relation to the body but your pinion will move up and down as your rear suspension loads and unloads.

I'm out a here. I will go back to my building of cars that actually hook and leave this discussion to you guys :)

Hey now Madman, your experience speaks for itself.

After seeing what Madmans cars will do on the track, I'll go with his way any day. Keep up the good work Madman.

I'm out a here. I will go back to my building of cars that actually hook and leave this discussion to you guys :)
thanks for the input! it helped me out..

the suspension doesnt care if the pinion is parallel to the ground. the reason for putting -2 degrees on the pinion is so that when under load it will be as close to zero as possible. in other words, while your going down the track under load, your driveshaft wouldnt even need u joints... it could be a solid shaft in a perfect world.
setting it off the ground could net you -5 or whatever, and you might still have -3 degrees while your going down the track. not the way to do it if you ask me.

pinion needs to be measured in relation to the driveshaft, and also you need to make sure the trans yoke is good in relation to the driveshaft.
my car is setup to zero angle on the front u joint, and -1 degree pinion angle. 1.32 60' so far with a car making around 420-440rwhp on the bottle. 28" tire.

Thanks for your help Madman.

I have done it Madman's way and Wolfe's or Rossler way (which is not referenced here) and I had had better luck with taking the 2 angles rather than just the one.

Someone may find this link useful:
http://buickperformance.com/Pinion.htm

fwiw, when I set cars up, I go off the difference of the 2 angles. Pick a way your successful with and stick with it. Madmans right, We all have different ways of doing it and no one will ever agree.

gollum... thats a great link for the most part. thanks for posting it. some of it is a little off like:

Straight Scoop: You've got to......... It so happens that professionally built racecars
are constructed so that the crankshaft is parallel to the floor,
meaning that .................


Thats not realy the case. Let's say for example im building a car with around a 9.5" crank height, and im running a 34.5 tire on the rear. I build my cars to have a straight shot from the front of the crank through the trans straight into the pinion on the rear. This car would have the engine/trans centerline going uphill from front to back(trans output shaft higher then front of crank). The driveline parallel to the ground in this application wouldn't accomplish anything. Once the car is built, I then stick about -1.0 to -1.5 degrees pinion angle on a heim joint car.Once the rear tries to wrap up, everying idealy would be completely straight and the u joints wouldn't have to overcome any angles and sucking up any horsepower. but anyway.. thats just how I do it......

I build my cars to have a straight shot from the front of the crank through the trans straight into the pinion on the rear. Once the car is built, I then stick about -1.0 to -1.5 degrees pinion angle on a heim joint car.Once the rear tries to wrap up, everying idealy would be completely straight and the u joints wouldn't have to overcome any angles and sucking up any horsepower. but anyway.. thats just how I do it......

This makes verygood sense when bulding a racecar from bottom up. Is pointing the trans strait at rear pinion easy to do with our stock late model Fbodies?

This makes verygood sense when bulding a racecar from bottom up. Is pointing the trans strait at rear pinion easy to do with our stock late model Fbodies?
this is how i did mine. its a 3rd gen, but i would imagine a 4th gen wouldnt be much different. i wound up raising the trans. tailshaft up some.

gollum. Its possible but you need to determine the size rear tire your going to run and then the ride height you want before you do anything. When you get them real low, a lot of times the torque arm hits the transmission tunnel so you have to modify that

http://buickperformance.com/Pinion.htm

****edit, oops, saw this link was already posted....lol O well



Myth #1: The pinion angle somehow affects how much traction the car
will achieve.

Straight Scoop: No way. The pinion angle doesn't mean squat as far
as the rear suspension is concerned. Think about it: why would the
suspension care about u-joint angles? What determines the "hit" on
the rear tires and the rate and amount of weight transfer is the
intersect point of the upper and lower rear bars (control arms).
That's known as the "instant center" (IC), and combined with weight
distribution, spring rates, and shock valving is what affects
traction.

Myth #2: You increased the pinion angle and the result was increased
traction, so Myth #1 must be correct.

Straight Scoop: You haven't been listening. Pinion angle doesn't
affect traction. What happened is you shortened the length of the
upper bars and that changed the intersect point, moving the IC
farther forward. You also screwed up the pinion angle in the
process. If you want to change the length of the upper or lower
bars, or change their mounting points, that's fine. But after you're
done you've got to go back and check and properly reset the pinion
angle.

Myth #3: The garage floor is the correct reference point for
measuring the pinion angle.

Straight Scoop: You've got to be kidding, right? The garage floor
doesn't have anything to do with anything. What's important is the
drivetrain angle. It so happens that professionally built racecars
are constructed so that the crankshaft is parallel to the floor,
meaning that the transmission output shaft will also be parallel to
the floor. But this usually doesn't hold true for cars using a
factory chassis. In most of those cases the engine is tipped
rearward. Take a look under the hood of your Buick and you'll see
what I mean. The drivetrain angle is the reference point and is
considered to be zero.

How to Measure It: The best way to do this is with the car supported
on jackstands, with stands under the front control arms and rear axle
tubes, with the full weight of the car resting on the stands. Next,
it's best to remove the driveshaft. Using an angle finder (these are
available from Competition Engineering or at Sears Hardware stores--
they're a commonly used carpenters tool), measure across the surface
of the rear transmission seal vertically(see illustration 1). This
surface is perpendicular to the output shaft of the trans, so
subtract the measurement from 90 to get the drivetrain angle. Let's
say that the measurement is -2 degrees(pointed down). That is our
reference point. Look at illustration #3. The pinion angle is the
difference in the angle of the rearend to the angle of the
drivetrain. So, in order to have zero pinion angle, the rearend
would have to be tipped upward (pinion yoke pointing upward) 2
degrees. If our drivetrain angle measured -5 degrees, we'd have to
tip the rearend upward 5 degrees to have zero pinion angle. Get it?
Now turn the pinion yoke so that the u-joint cups are sideways, and
measure across one side of the pinion yoke vertically(see
illustration 1) where the u-joint strap connects. Again, this
surface is perpendicular to the pinion, so subtract the measurement
from 90 to get the rearend angle. compare this number to the
drivetrain angle to get the pinion angle. If the drivetrain angle
was -2 degrees(pointed down), and the rearend angle measured +1
degrees(pointed up), then the pinion angle would be -1 degree. If
the drivetrain angle had measured -2 degrees (pointed down) and the
rearend angle had measured -3 degrees (pointed down) then the pinion
angle would be -5 degrees. In my particular case, the drivetrain
angle measured -4 degrees, and the rearend angle measured -6 degrees,
resulting in a pinion angle of -10 degrees, a wasted tailshaft
bushing, and a slower than necessary racecar. The idea is to have
the pinion angle at zero with the racecar under power and going down
the track. To allow for suspension movement and loading, the pinion
angle should be at around -2 degrees for our cars.





if your overall driveline angle is not close to zero you can possibly introduce high speed vibrations from the difference in angular velocities of the u-joints. u joints are not CV joints and are not made to be run at different angles relative to each other. I had a high speed vibration that I got rid of by simply adjusting my pinion angle to match my tranny output shaft angle so both of my ujoint angles are the same (0° driveline angle). When I think of a -2° pinion angle that means that my pinion is tipped "downward" 2° from a 0° driveline angle.

I think the 4th gen is designed so that the driveline is even with the frame, I recall talking to Mike @ Yank about automatic transmissions and I thoght he said that the 4L60E is designed to be parallel to the frame/ground.

well despite everyones differance's... thers deff. enough info here for anyone! Many different ways to set it up. Thanks