oakley6575

iTrader: (3)

I'm trying to set up my pinion angle for when I add traction bars. As it sits right now, I measured the following angles:

Trans yoke 6* down toward the ground
Pinion is 6* up toward the roof
Driveline is 0* or parallel with the ground

From all the drivetrain articles I've read, the working angles need to be equal and opposite like they are above but shouldn't they be 3* or less. 6* seems to be a lot.

Also, I'm trying to set my pinion angle to improve traction. If the pinion angle is +6* right now, I can only imagine that it gets worse (+9* or +10*) under acceleration. Do I need to set the pinion angle up to -3* so it climbs back up to 0* on launch?

If I do that, I would have to add a 9* shim to the rear end. Do I need to raise the trans the same amount, or back to 0* to compensate? Thanks guys

1 FMF

iTrader: (1)

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

the top image "perfect inline" is actually incorrect. the universal joint between the drive shaft and yoke (either end) needs to be at a 0.5° angle or greater. max operating angle there i think is something like 5° but you need some angle more than zero so the ujoint trunion rotates in the cap. when it doesn't rotate is when the needle bearings in the ujoint wear out because they don't move and lubricate themselves with the grease that's in there.
how much angle also depends on the ujoint size, the GM 3R because it's small is a small angle. a 1410 ujoint like on my truck has a much larger operating angle and you can easily see that angle looking at how the drive shaft points downward from the transmission to the rear axle.
in the pic the second one down "parallel" is everyone's situation and in your case you said your trans pointed down 6°. so you need to have your pinion at the axle pointing up 6° to be zero'd out and no vibration. the definition at least to me of pinion angle is the difference of those two angles: if trans points down 6° and axle points up 6° then you have 0° pinion angle. if your axle points up only 4° then you have a -2° pinion angle or a 2° downward pinion angle- which may get closer to the ideal zero under load. and these angle measurements are using an angle finder with the angle relative to earth or gravity.
so it's a matter of accounting for deflection in the drive train under load or whatever conditions the car will see. the axle will rotate and make the pinion point upwards under load- looking at car from driver's side the rear wheels rotate counterclockwise moving the car forward so the axle will want to rotate clockwise. how much it does depends on what parts you have, i have an umi adjustable and when i measured mine i tried loading the axle with a jack to see how much it would deflect upward and it was less than 0.5°. because you have an adjustable torque arm, i would adjust there and not bother shimming the transmission.

how the idea of pinion angle helps with traction i don't understand and don't believe in.

oakley6575

iTrader: (3)

I dont' have an adjustable torque arm. This is a 2003 Silverado. Thanks for the response. Seems that I get a different answer from every person I ask.

Your saying that pinion angle is the difference in trans yoke and pinion. In that case I would have a 0* pinion angle. I've been told that pinion angle is (pinion - driveshaft) where the trans yoke doesn't have anything to do with overall set up. If that was true, it would be a +6* pinion angle. Also, I've been told that if my driveshaft is at 0*, then the pinion needs to be pointing down 3-4 degrees. I hate when there isn't a definitive answer

Slowhawk

iTrader: (12)

Just another thought. If this is for the truck listed in your sig I would not even bother with a single shaft. I would go directly to a 2 piece shaft. We've destroyed a few 1 piece shafts in trucks like yours. never broke a good 2 piece.

garygnu

you usually want a negative rear end angle down,under power it should twist up for a straight alignment .with a leaf spring rear end you could try angle shims between the rear axle tubes and the springs.

1 FMF

iTrader: (1)

well the definitive answer was in the hotrodhotline link i posted giving the article titled "drive shaft harmonics". did you read that?

"pinion angle" is not simply (pinion - drive shaft)
(pinion - drive shaft) is the u-joint operating angle at that location. for a single piece drive shaft you have a cardan joint (a.k.a universal joint) at each end so you have whatever u-joint operating angle at the rear axle pinion and at the transmission yoke. A u-joint operating angle should be kept as small as possible and 3° or less is recommended for the best vibration free performance. but for things like trucks when they are lifted a u-joint operating angle and can up to 30°. The greater this operating angle and the faster the drive shaft or u-joint spins the more vibration there will be.

when most people refer to "pinion angle" which is a slang term used out of context by people who don't know, what is really meant are the two operating angles of each u-joint at the ends of the drive shaft. those two angles need to be the same or as close to each other as possible otherwise that will cause vibration- if those two angles are the same then mathematically one subtracted from the other is zero. so from that is why it's said you always want a zero degree "pinion angle", you want the operating angles of the u-joint at each end of the shaft to be the same.
but the angle at that u-joint (between the axle pinion and shaft and between the shaft and transmission yoke) can be up to a certain amount that is why they are used in the first place.

lees02WS6

iTrader: (5)

1 FMF has it correct. Though the config pictured at the bottom is debatable. According to the mathletes that configuration is actually acceptable as long as it is composed of equal angles. GM used it on several cars, it's called the 'W' or 'Broken back' drive line.

oakley6575

iTrader: (3)

I did read the link you posted. So by the link, I need to bring my operating angles down from 6* to something under 3*. But it only makes sense to me that my angles need to be 0 under load. When they are zero under load, the most power can be transferred to the pinion. Is this true?

We all know that the pinion will rise under power so why don't we take that into account when setting up these angles? Lets say I keep all my angles the same except I drop my pinion down 3*. So I have my trans pointing down 6*, driveline parallel, and the pinion pointing up 3*. Would I get vibration under normal city driving? And when I'm at the track or I go WOT, would my pinion rise the 3* causing my working angles to cancel out and be 0?

Sorry for the questions but I'm just trying to understand the process.

lees02WS6

iTrader: (5)

these angles sound extreme to me. Are you measuring with the car level, and the suspension loaded? The tail shaft should be between to 2° and 3° sloping down. The rear end should match.

The pinion will try to climb the ring gear, so if this is drag racing you should account for that, but for street driving match the angles.

lees02WS6

iTrader: (5)

these angles sound extreme to me. Are you measuring with the car level, and the suspension loaded? The tail shaft should be between to 2° and 3° sloping down. The rear end should match.

The pinion will try to climb the ring gear, so if this is drag racing you should account for that, but for street driving match the angles.

oakley6575

iTrader: (3)

I measured the pinion and driveshaft with the truck on a level surface at ride height. I measured the trans angle on lift.

lees02WS6

iTrader: (5)

Ah ok. I missed that part. Your engine and transmission are angled too far down, you really need that tailshaft at 3° or less. Then you can get your pinion to match.

If you're still having issues you might want to look at double cardan joints, at least at the transmission. A double cardan will split the difference at the tailshaft, and the pinion should be pointed up at the transmission (with one double cardan joint). 6° is quite a lot of angle for the joint to cancel vibration. What size joints are they, 1350?

SSellers

Your angles are not extreme. It's a truck so the physical orientation is different than in a car. The lower the engine sits in relation to the rear end, the smaller the angle of the transmission yoke will be with respect to the vehicle's centerline. In a truck the engine typically sits higher so in order to keep the working angles of the u-joints in correct range you have to tilt the transmission down more, which means the pinion gets tilted up more. Worry about your u-joint angles, not so much the angle of the yoke and pinion with respect to the centerline of the vehicle. If you were to try to set you transmission angle to something like 3 degrees and then set your pinion to 3 degrees up what you would most likely run into is the u-joint angles being whacked.

Your numbers look pretty good (without knowing the actual pinion angle). To run smooth going down the road and have long u-joint life you want two things:
1. Transmission yoke and pinion to be parallel with each other. You've got that.
2. Pinion angle (angle between pinion and driveshaft) to be in the range of 1-3 degrees which is the typical working range of a u-joint on a vehicle that is NOT strip only.

If your pinion is 2 degrees down in relation to the driveshaft and parallel with the transmission, that means your pinion can climb up to 5 degrees during acceleration and still be within the working range of the u-joint. On drag cars it is different depending on both suspension type and power level. In a high horsepower vehicle the pinion may climb more so you may see a recommendation to set the pinion at -6 or -7 relative to the driveshaft. This is because if the car hooks the pinion is going to climb and as it does so it will climb into the correct working area of the u-joint so to speak. This is for a dedicated strip car. If you daily drove something like this you would experience very short u-joint life.

I'm one of the guys that usually throws the term "pinion angle" around loosely and wrongly, but I also call an engine a motor sometimes.

lees02WS6

iTrader: (5)

Even with a truck, or a 4x4, the principles still apply. Any angle is going to eat into the operating angle of the driveline, but in addition larger angles make it more difficult to cancel vibration.

You still want to keep the angle with .5°, and with respect to a level surface at 3° or less

SSellers

I blew past the part where his driveshaft was essentially 0 degrees when referenced to the same point as the pinion which was the ground in this case. At these values the angle of the pinion and yoke compared to the ground do not matter. It's the angle between the pinion and driveshaft that do. In this case, the driveshaft just happens to be at 0 compared to the ground and the pinion at 6 compared to the ground so yes, the pinion needs to come down at least 3 degrees and the trans up at least 3 degrees to get into the working range of the u-joint OR the rear end needs to move down relative to the engine so the driveshaft slopes at least 3 degrees.

oakley6575

iTrader: (3)

This is what I mean about getting a different answer from each person I ask.

Thanks for your guys input. As it sits right now, I don't have a single vibration. It runs smooth as glass. The only reason I brought this up was because I have never been able to get traction with this truck. I will be adding traction bars soon and thought if I need to adjust angles, I will do it at the same time.

What would be the optimal solution for me?



How do I satisfy both of those in my case. I would have to raise my trans 8* and the opposite with the pinion. That would put my trans 2* up and my pinion 2* down. They would be equal and opposite and my pinion would be able to travel 5* under load and still be in the 1-3 degree operating range? ? ? ?

lees02WS6

iTrader: (5)

Ah, well that's a different issue entirely. Forget about the driveshaft, that truck probably has leaf springs. Your issue has more to do with tires, spring wrap, and instant center.

Caltrac bars (traction bars) to keep the leaf's from wrapping up under acceleration are where to start.

oakley6575

iTrader: (3)

I'm going to use Assassin Bars from Smith Racecraft. Adding those won't change my pinion angle when the truck is stationary will they? Thats why I'm trying to get a good idea of what I need to do to my angles before adding those bars.

lees02WS6

iTrader: (5)

They can. Just measure the angle before and after. If you shorten them they will raise the pinion, and lengthening obviously will do the opposite.

All you're doing is reducing spring wrap. It does help maintain the pinion angle much better, but not as well as a third link in combination with those would.

before


after

oakley6575

iTrader: (3)

Those are pretty cool vids and really put it in perspective. If you go to the 11:00 min mark on the second vid, he is slowing down and then gets on it. You can see the pinion rise quite a bit. Is that a bad angle between the pinion and driveshaft when he does that?