MADMAN

iTrader: (4)

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

GIZMO

iTrader: (8)

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

MADMAN

iTrader: (4)

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?

GIZMO

iTrader: (8)

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.).

Magnus

iTrader: (4)

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.

Magnus

iTrader: (4)

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."

JL ws-6

iTrader: (50)

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?

Magnus

iTrader: (4)

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

MADMAN

iTrader: (4)

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.

JL ws-6

iTrader: (50)

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.

MADMAN

iTrader: (4)

It should be parallel JL

JL ws-6

iTrader: (50)

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!

Matt D

iTrader: (49)

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.

JL ws-6

iTrader: (50)

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

GIZMO

iTrader: (8)

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?

JL ws-6

iTrader: (50)

I would

GIZMO

iTrader: (8)

Please explain why.

MADMAN

iTrader: (4)

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

JL ws-6

iTrader: (50)

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.

Magnus

iTrader: (4)

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 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.