lwmulno1

New to me 2000 Camaro SS, manual trans, dynoed at 602/603 RWHP/TQ sprayed, QP fabricated bolt-in 9", adjustable UMI torque arm and LCA's. Will be primarily a drag car, currently on street radials. Never raced by me.

Several years ago I built a blown pro street '68 Nova back half 4-link car in my garage, FAB-9 rear, setting the trans angle down 3 deg, pinion up 3 deg, the thing never vibrated, no problems, ran on the strip several times. Why am I seeing so many different suggestions to set this Camaro up, from using the shaft angle/pinion angle to measuring all three angles and doing math, etc.?

At my age I'd rather not be crawling under this car a lot, would like to get it right the first time. The most reliable post I've read the OP set his drive shaft at zero deg, pinion up 2 deg with no issues. I'm at 2.5 deg trans down, 2 deg pinion up which puts the shaft at or near zero.

Any thoughts without going into an elaborate engineering discussion to make this easy out of the chute?

Thanks, Larry M.

BMR Sales2

iTrader: (40)

This is the method we suggest:

lwmulno1

Thanks BMR, I've seen that video, so it would mean with my tail shaft at -2.5 (down) I subtract minus 2 from that and set my pinion angle at - .5 (down)? I apologize I can't wrap my head around that setting, seems the pinion should be adjusted up some degree past zero (offsetting the tail shaft down angle). Am I over thinking this? I think what I neede is for someone to tell me what to set the pinion at in degrees, positive or negative (up or down). I would really appreciate that.

The video says subtract 2 from the tail shaft angle, does he mean subtract -2?

I understand the setting will vary under hard acceleration perhaps, but can deal with that if there's an issue down the road.

War Prayer

Hold your hands out flat in front of you with your fingertips touching each other. Now fold your hands like the roof of a house, fingertips up, wrists down. Imagine your left hand is the tailshaft, and your right is the pinion yoke. That's POSITIVE pinion angle. Bring your hands back parallel, that's 0 degrees, now keep raising your left wrist until you make a "V" with your fingertips down below the plane of your wrists. That's NEGATIVE pinion angle.

That's the only way my idiot brain could ever understand it, hope that helps.

One of the BMR videos shows the correct method but gives the math wrong IIRC. I think they fixed/updated it at some point though.

-2 is what works for most people, and what has always worked for me.

War Prayer

This diagram may also be helpful.

lwmulno1

I understand the positive and negative angles bu not the math I'm seeing online. I believe the pinion angle is to be opposite the tail shaft angle and assume it's suppose to be positive in relation to the tail shaft.

For you -2 works, measured where? What are your numbers, negative tail shaft degrees and pinion degrees. I mean is your pinion down 2 degrees from level/0, 2 degrees less than your tail shaft, I'm upside down right now, and probably asking this wrong?

My tail shaft is down 2.5 degrees, where should my pinion be up or down (from level) and how many degrees? At 75 I may be losing my mind...ha ha

War Prayer

The problem with the math is that you can do it either way, if a downward slope towards the intersection is negative then you add the two numbers. If downward slope is positive then you subtract them. See the first image I posted for an example of the former. See the image below for an example of the latter.




I measure the first way, so I reach -2 by adding my driveshaft and pinion yoke together. Adjusting the torque arm moves the rear end, so assuming my DS is a static +1 I would adjust my rear end angle to -3. (+1) + (-3) = -2

At 75 years old I’d say you’re kicking *** and taking names!

lwmulno1

I get it now War, thanks for your patience. For some reason I didn't think the pinion could be at a down angle, but it makes sense figuring the rear end rolling up under load.

About the 75 thing, I only feel it getting up off the cold shop floor when a creeper won't fit under the car, ha ha. Thanks again. Larry

LLLosingit

iTrader: (4)

For years most drivelines (motor/trans) were mounted 3* down from the factory so most people would angle the pinion at 3*up that way both U-joints angles basically cancel each other out, The only time a person needs to worry about the driveshaft working angle is when you're dealing with a lifted truck where the driveshaft is at such an extreme angle that puts the u-joints are under quite a bit more stress.
Here is a simple way to understand why you need to have opposing angles match.

"Unfortunately, as the front U-joint gets the power delivered to the driveshaft, it transforms smooth engine power into pulsating power. This happens because the U-joint travels an elliptical path caused by the angle through which it operates. You can visualize this by looking at a dinner plate straight on. If you tilt it the round plate appears to become an ellipse. In traveling this ellipse, the U-joint speeds up and slows down twice per shaft revolution. A second U-joint having an equal but opposite angle is used to convert this pulsating power back into smooth power feeding the pinion. The bigger the working angles are, the more violent these speed changes become."

War Prayer

Awesome, glad to hear it. Yes, you’re right about the rear end rolling. I guess what you’d call axle wrap on a leaf spring car. You’re setting preload so that when you’re up on the throttle things are lined up as they should.

I can only hope to still be crawling under cars in another 40 years.

lwmulno1

Equal opposing angles is what I had
in my solid 4-link car. What War describes that works for him has both angles negative but using the DS angle vs. tail shaft, assuming under moderate load angles would change to opposing or at least zero. Just my thought.

Thanks for the reply

War Prayer

Correct, I have never measured from the crank pulley, trans, etc. always used the DS vs torque arm bracket. Not necessarily because that’s right but because it’s so much easier, haha.

I have also had my car professionally aligned by Vengeance (big name shop in Atlanta area) and they told me my pinion angle didn’t need any changing so I guess it did it right.

lwmulno1

I'll do the same this afternoon, I'll zero/level the pinion, measure my DS and do the math to get -2 deg, maybe just put -2 on the pinion and see where the DS is at. I'm in Wasilla, Alaska, we had a bunch of snow last night with 7 or 8 days more forecast, fortunately, (for me, my son and the neighbors I like, ha ha) I have a plow on my truck.

I'm about to wrap up the winter upgrades, 9" install, cage, scatter shield, etc, this pinion thing is the last, our race season doesn't start until Mothers Day. Input from you guys is great, thanks to all. Larry