I think I have my pinion angle set wrong and its giving me a vibration.

The driveshaft is sloped to the rear at a 1* angle and the pinion yoke is pointed towards the ground at a 1* angle. So my angle would be at 0* right?

So if I want a -3* angle I would have to add 3* more angle to the pinion yoke (aimed more at the ground) correct?

Thanks in advance guys

 

Anyone?? I watched a couple videos on youtube and I just wanted to make sure I had the measurements correct.

My angle on the DS would be +1* and my pinion would be -1* so I should add 3 more degrees to the pinion aiming it towards the ground a touch more to give me a -3* pinion angle??

 

Bumpity

 

according to bmr, you should be measuring at the plate of the rear end. Maybe that's what you're calling the yoke. Anyway if your DS angle is neg one as it is. Then put your angle finder on the rear plate by the mounting screws. adjust until the rear slopes down toward the front of the car by - 1. Double check to make sure your ds angle didn't change and you're good to go. If you're like me though, there may be trouble because everytime I changed the rear end angle with the barrel nut. the DS angle changed. It tried to stay at neg four. So you're not far off. It should take only a quick adjustment. It helps to write a little chart with directions and pos/neg before getting under the car.
good luck

 

I thought that my DS angle was positive and the pinion angle was negative (according to BMRs video on youtube). I don't have a plate style TA to measure from. I have a MWC axle package so I measure from the actual pinion yoke.

 

I use the bmr you tube video, make a chart based on what they say halfway thru then get under the car

 

The pinion angle needs to be set parallel to the engine/trans angle. In a F-body (stock ride height) the engine points down 3-4deg, so the rear needs to point up 3-4deg. All the -2 / point the rear at the ground advice comes from guys with drag setups where the car has a lot of rake and the engine is probably level in the car. I speak from experience after chasing a vibration for a while.

 

I'm not trying to sound like I'm arguing with you, but that's the opposite I was told.

I was told that the driveshaft and rear pinion should make a "V" The driveshaft on my car is pointing down towards the rear axle at a 1* angle (that would be a positive angle correct?) and my pinion angle (measured off the pinion yoke) is set at 1* pointing down towards the ground (that would be a negative angle correct?). So with that said my current angle would be at 0*

I haven't had a chance to get my car on the lift lately, but I was going to add another 3* to the pinion to make it a -3* angle and see how it feels. I also need to pull the driver side header and flatten one of the primary tubes so it quits vibrating my dash like crazy. I also have to trim my rear seat brace so it stops hitting my TA on bumps.

 

Set pinion at -2. Your pinion may be rotating up and past your -1 driveshaft angle.

 

I agree with what Fall Line said about making the trans and pinion parallel. I fought a vibration for years because I was following what everyone said about the -2 compared to the driveshaft and I could never get rid of the vibes. As soon as I made the rear pinion parallel to the trans all of my vibes went away. The -2 is for drag racing not daily drivers. Even if you wanted a -2 it would be 2 degrees below parallel. Don't even put the driveshaft into the equation. This has what worked for me anyways.

 

Fall Line does have it right. The pinion yoke and the transmission yoke should be at equal and opposite angles for a street driven car. For quarter-mile racing, "they" say to put your pinion angle down 3-4 degrees so that when you get on the gas, and the rear end squats, your pinion angle will be equal and opposite to your transmission yoke under acceleration. I had some guy in AutoZone tell me about putting my pinion down a few degrees and I called him on it. Rather then starting an argument in front of customers, and because I had $hi^ to do, I just agreed to disagree and left. I have not been back. It is some sort of urban legend about the pinion pointing downward, or folks are taking what works at the strip, and trying to apply it to the street. It don't work folks. Now, that 3-4 degrees down is dependant on your rear suspension geometry, and is just a WAG. But to repeat, your pinion angle, for a street driven car, should be equal and opposite to your transmission yoke - so that a line drawn through the center of your transmission, and the center of your pinion gear, are parallel. I just did some extensive research on this, and adjusted my pinion angle to match my T56 (custom 72 Chevelle LS3/T56 setup).

Tom Ringlein

 

Most of this info is actually right on track. It really depends on your application, whether or not you're launching a drag car and what type of rear suspension you have.
A hard launch (drag car) makes the pinion climb the ring gear very hard and push it upwards as it climbs. This is why pinion snubbers are so common on stock type suspension 60's muscle cars. If your rear suspension allows too much climb, your Ujoints are forced to contain that movement..often leading them to fail.
The downside to this type of adjustment is that daily driving has your Ujoints in a constant state of bearing the permanent negative angle. Check an OEM rear wheel drive sometime. You'll see it's very close if not right on 0 drive angle degrees. Thats to minimize vibration.
OP, if you're looking at your angle finder gauge from the driver's side, when you measure the driveshaft anything to the left of zero is negative angle. When you measure the pinion yoke(preferably...the torque arm bracket if you have to), anything to the right of zero is negative. Some of the formulas I've seen on here cause confusion and their math is way off. I've seen some people recommend subtracting a negative value and they don't use conventional math of subtracting a negative becoming a positive so its screwed up.
When I set mine, I use total negative drive angle........the "V" you're referring to. I've done this in the past and its always spot on. I have noticed that with this type of aftermarket torque arm suspension many of us run you "feel" negative drive angle in daily driving more so than you would in an older style Pinion snubber/leaf spring application.
BMR recommends adding the negative values. If I'm reading your figures correct, I would say you have -2 degrees of drive angle. What you're looking for is in the application of torque to the pinion, you want as square of a ujoint as you can ( tranny-to-pinion yoke as straight of a line as possible) to minimize chance of breakage.
From that perspective, now you have to figure out what you're shooting for...maximum dependability for hard drag launches, or minimal vibration for daily driving.
You're pick, you just have to live with the pro's and cons of your adjustment.

 

Thanks for the responses guys.

I downloaded MWCs pinion angle instructions again last night and I was wrong with my measurements and how I was figuring them.


So for the best setup for a DD I would want to measure the transmission and the driveshaft and set the pinion angle to match the front U-joint angle right?

Thanks again

 

It was easier for me because I had no driveshaft installed when I did mine. DON'T MEASURE THE DRIVESHAFT!!!!! I went down to Harbor Freight, grabbed a magnetic digital angle finder (about $20), and "stuck" it to the transmission output shaft. Got 3.8 degrees down. Went to the rear and "stuck" it on the pinion yoke (making sure the pinion yoke was horizontal to the ground) - and adjusted it for 3.8 degrees up. My angle finder does not measure angles more than 90 degrees, so this is how I did it. I have a minor in mathematics with emphasis in geometry/trigonometry - so I know how it worked. As long as your vehicle is at its ride height (I had to add weight to my unfinished car to do that), and your angles are relative to a flat surface, the angles will be correct. Note: I never measured the angle of the driveshaft - that gets confusing and unnecessary. It is this easy - measure the angle of the Transmission output shaft and the angle of the pinion yoke. They should be equal but opposite angles - transmission pointing downward, pinion pointing upwards.
I added 40 gallons of water to the trunk, and 30 gallons or so on the front to simulate a full tank of gas and various parts of the car that are still in boxes. Now that the car is nearly complete - the angles are still at 3.8/3.9. I have pictures that I might add when I get back to my hooch.

TJ

 

This is how an oem is set up I think where engine mounts, tranny mount, and rear suspension geometry is known. I'm guessing because of your mods OP that some racing is in your future. Just beware that a pinion transmitting gobs of torque at 5 or 6 grand WILL want to force the pinion up. Then its a question of how much bending and angled stress can that little ujoint take.
If you're not racing, you'll probably be okay. If I would have tried running a 1:1 angle ratio on my Super Stock car, my ujoints wouldn't have lasted 1 pass. Slicks and torque change the game dramatically. Ask the guys on the strip who are making consistent fast passes with good 60ft times....and not breaking.

 

http://www.hotrodhotline.com/md/html..._harmonics.php

 

The thing about universal (cardan) joints is that in actual fact it seems they cannot really operate at an angle. What I mean by that is a single u-joint will only produce constant velocity, vibration free, when it is not at an angle to the yoke or the shaft it’s attached to. The moment you apply an angle it will cause the shaft to wobble, as the joint angle increase so does the wobble or vibration.

A standard drive shaft, with a u-joint on each end, will only produce a constant velocity when those two joints are parallel to each other. Forget the number of degrees, they are a reference, if the car’s nose is up in the air or buried under ground the relative number of degrees between the transmission output shaft, and the yoke at the pinion is what is important.

Anything other than compensating angles (at least close any way) will produce bearing killing, u-joint wearing, pinion seal leaking shake and break.



It seems to me that the reason people are given the suggestion to run opposing angles of any degree is to compensate for pinion rotation. In a drag race when its power on through the whole quarter mile, the pinion will rotate up.

If you have 3° down at the tailshaft of the transmission, then you want 3° up at the pinion while power is being applied. If you have 3° of rotation when power is applied, and started with 3° of static alignment at the pinion, you’d have 6° up of pinion angle with all the juice applied (way too much).

The idea for drag racing it seems is, you start with a lower number at the pinion yoke (opposing angles), and under power it will rotate up to the compensating angle. The V (often called broken back config or W) config is that driveline angle where both angle are opposing.

For other types of driving you want equal opposite angles, second diagram down. The third diagram will make vibration worse in all cases, except drag racing.

 

Great article.

That is exactly how I set my pinion up and have no issues.

 

Thanks guys, thats a ton of good info. Way better than some of the info I have found.

I will pull the driveshaft this weekend and measure the rear output angle and then set my pinion angle to match and see how it feels after that change.

 

lees02WS6>>> Awesome pictures! That illustrated it a helluva lot better than i was explaining it. Once the OP sees this it will make more sense. I would hate to see him break a u joint on his first hard launch with good tires.
Drag racing and daily driver setups are different, the pics show it well.