Optimum driveline angles for vibration free high speed operation.

[83hurstguy]

I figured this is a good thread to add my experience with pinion angle along with some questions. I messed with my pinion angle last fall, and due to other issues finally got the time to work on the car this weekend. I also bought some better tools to get more consistent measurements. My G-body H/O has a 200-4r trans and GM 8.5" 10 bolt with Eibach springs and Currectrac rear control arms.

When I measured the pinion angle initially this weekend, the picture below shows the values I recorded. Note that the angles shown are absolute, and not adjusted for garage floor pitch (approximately 1* down towards back of car, but shouldn't matter as all tires are at the same height on race ramps).

The u-joint angles were not canceling, due to the car being lowered. My next step was to figure out how high I could raise the transmission... I was only able to shim it up 3/8" before the Olds power steering pulley gets reallyclose to the steering box. This was not enough to reverse the angle at the front u-joint to run a traditional driveline configuration (with the pinion angle down relative to driveshaft).

As I see it, I have two options... either get a new driveshaft with CV joint at the front, or run a reverse driveline orientation where the pinion is up relative to the driveshaft. (A third option is significant engine bay surgery to raise engine/trans with custom mounts, but that's immediately ruled out, and hood clearance is already at a premium).

I set the car up with the reverse driveline orientation today with the shimmed transmission mount. The picture below shows the best that I could get at the end of the day.

Does anybody have any thoughts or comments on my setup? Am I missing any other options? I left the pinion angle at this position to account for 2* of pinion rise under power, which would then lead to 2.4* total working angle in the rear. Is 0.4* enough initial angle, or should I have closer to 1* in there static (to ensure u-joint rotation), which would bring it to 3* working angle with an estimated 2* pinion rise?

I can't say I'm happy with it, but I think it's the best I can reasonably do for now. Thanks in advance for any feedback!

[andrewb70]

Luke,

That seems like a very reasonable starting point.

Andrew

[83hurstguy]

Luke,

That seems like a very reasonable starting point.

Andrew

Thanks Andrew! Appreciate all your help and info shared with your experiences.

[icemanrd19]

I'm seeing all of these engine measurements but where are you taking them from? I have my t56 way up hitting the floor and the floor is already raised about a 1" or so.

Im using dse subframe, dse plates, and the angle from the oil pan seems pretty steep still. Everyone is taking these at the car sitting ride height correct? Couldn't i just cancel my transmission angle with adjusting my rear quadralink to compensate for it?

[bryant]

you can take the engine/transmission angles on any surface that is parallel or perpendicular to the the center line through the crankshaft and transmission shafts. like the front face of the blancer or front pulley. along the oil pan rail or valve cover rail, on the back of the block or front of the bellhousing.
the car does not have to be level. the weight of the car needs to be supported on its suspension to have the differential at ride height.
yes you can cancel or the engine/transmission angle with setting pinion angle. just make sure the operating angles on the u-joints dont become too much. the tremic driveline app works very well at determining all of this and its free.

[icemanrd19]

revived.

Currently my engine angle off the balancer is 4 degrees. I can't go any higher on the rear of the trans because i only have 1/2 clearance between my headers and floor. With the rear quadralink i can adjust it to set my driveline angles if need be but having the engine at 4 degrees isn't a big deal is it?

[72BBSwinger]

That's a little more than normal but liveable.

[icemanrd19]

not sure what else to do.

how close can i get the headers to the floor without causing issues? Right now my knuckle can bairly get in between the headers and floor

[72BBSwinger]

Split the difference and raise it a 1/4". Also I level my rockers THEN set my angles. Cars almost always have SOME rake at ride height. Doesn't really matter at the end of the day because you need the pinion about 2* below parallel to the engine angle but still opposing angles to cancel the u-joints from vibration.

[icemanrd19]

Engine 3.92 degrees down
driveshaft 1.10 up
pinion 2.2 degrees down

All angles are looking at it from the passenger side.

I can't move my transmission up anymore. Do i move my pinion angle up or down?

[icemanrd19]

the driveshaft shop gave me some good advice whenever the driveshaft is climbing uphill

can you give me the info off the car like this

1. engine/trans is on ____ angle and it heads up in the back or down in the back
2. The Driveshaft (if not there use a string or a piece of wood to go from the center of the output shaft to the center of the pinion) ____ angle and it heads up in the back or down in the back
3. the pinion ______ angle and it heads up in the back or down in the back
-------------------
Please take not how i have described the water running the parts to make sure were
both understanding the angle up/down thing.
So is the Motor and trans face down at the back (water would run off the back of the trans)
at 2.3 and the shaft heads up to the rear at .5 (water would run down the shaft towards the trans causing a puddle when meeting the trans) (you take 2.3go back to Zero and then up to .5 = 2.8)
the Front operating angle is 2.8

The shaft heads up to the rear at .5 (water would down the shaft towards the trans)
and the Diff points down at 2.5 (water would run off the diff toward the Shaft)
we would have 3 degrees
Rule is no greater then 3 and no more then .5 off, this (if measurements are correct)
would be 2.8 and 3.0 Text book perfect. if this is correct its either a issue with the yoke
not in the back of the trans enough or the shaft is not good.

[ctcz28]

Wow, this is an old thread. The article at the link below should be helpful:

https://www.hurst-drivelines.com/fil...roc_111606.pdf

[icemanrd19]

Engine is 3.34 degrees down, which raised the driveshaft to .5 degrees up at the trans and down at the rear diff, rear diff is pointing 2 degrees down. That gives me 2.8 degree front working angle and 2.5 rear. Just the slight 3/8 lift in the rear of the trans, bending the headers fixed my issue. Pretty much vibration free up to 125ish mph

[bing98]

Thanks for reviving this thread. It's a good read and perfect timing for me. I have been fussing with the angles and I am quite confused by all this. Right now my angle finder shows my transmission angle is 4 degrees down, the drive shaft is 1 degree down and the pinion is 2 degrees up. If I'm correct that gives me a 3 degree operating angle at each end of the driveshaft.

Much of what I have read says this is what I should strive for. That equal operating angles with ensure proper u-joint operation. Others have said the transmission and pinion angles should be equal, but opposite, which mine are clearly not. I suspect that if I adjust the transmission and pinion angles to be equal, but opposite the resulting driveshaft angle will change my operating angles to something other than equal.

So which is it? Equal but opposite transmission and pinion angles or operating angles?

I happen to be use that hurst-drivelines.com u-joint alignment procedure too. It's a bit confusing. They say to measure tranny, driveshaft and pinion angles like everyone is saying in this tread, but then they introduce some additional angles measured off of the u-joint caps themselves. They have you take the measurment off of the caps at the front and back and then rotate the driveshaft 90 degrees and take a second measurement. All 4 of these measurement on mine are very different.

[andrewb70]

Thanks for reviving this thread. It's a good read and perfect timing for me. I have been fussing with the angles and I am quite confused by all this. Right now my angle finder shows my transmission angle is 4 degrees down, the drive shaft is 1 degree down and the pinion is 2 degrees up. If I'm correct that gives me a 3 degree operating angle at each end of the driveshaft.

Much of what I have read says this is what I should strive for. That equal operating angles with ensure proper u-joint operation. Others have said the transmission and pinion angles should be equal, but opposite, which mine are clearly not. I suspect that if I adjust the transmission and pinion angles to be equal, but opposite the resulting driveshaft angle will change my operating angles to something other than equal.

So which is it? Equal but opposite transmission and pinion angles or operating angles?

I happen to be use that hurst-drivelines.com u-joint alignment procedure too. It's a bit confusing. They say to measure tranny, driveshaft and pinion angles like everyone is saying in this tread, but then they introduce some additional angles measured off of the u-joint caps themselves. They have you take the measurment off of the caps at the front and back and then rotate the driveshaft 90 degrees and take a second measurement. All 4 of these measurement on mine are very different.

I think you are confusing yourself. What you have now are equal and opposite operating angles. Remember, the measurements are taken relative to gravity, but your reference is the driveshaft. If you were to raise the back of the car by the axle so that your driveshaft was level, you would see that the engine is 3 degrees down and the pinion is 3 degrees up.



Andrew

[dondb]

I've read this thread and others several times and have one question. If the yoke out of the pumpkin runs downward to the rear of the car.....is that a positive or negative? I've had vibrations over 70 and would like to correct it. My current angles are 3-1/2 degrees at transmission yoke, 0 driveline and 1.5 degree's at yoke on pinion....running down hill to rear of car. My centerline on the transmission yoke is 9 7/8 and my pinion yoke is 10 1/8 from ground. I am running coilovers and trueturn on front lowered about 1 3/4 inches and Hotchkis leaf spring lowered 1 1/2" with a 12 bolt Moser. I have a LQ9 bottom end with LS3 top end running the full Holley swap kit. My wheels are Vintage wheel works....front tire is245*45*17 and rear 275*40*17. Any help would be appreciated I'm in winter Purgatory here in NH so i'd like to straighten this out before driving weather hits.

[andrewb70]

I've read this thread and others several times and have one question. If the yoke out of the pumpkin runs downward to the rear of the car.....is that a positive or negative? I've had vibrations over 70 and would like to correct it. My current angles are 3-1/2 degrees at transmission yoke, 0 driveline and 1.5 degree's at yoke on pinion....running down hill to rear of car. My centerline on the transmission yoke is 9 7/8 and my pinion yoke is 10 1/8 from ground. I am running coilovers and trueturn on front lowered about 1 3/4 inches and Hotchkis leaf spring lowered 1 1/2" with a 12 bolt Moser. I have a LQ9 bottom end with LS3 top end running the full Holley swap kit. My wheels are Vintage wheel works....front tire is245*45*17 and rear 275*40*17. Any help would be appreciated I'm in winter Purgatory here in NH so i'd like to straighten this out before driving weather hits.

Draw what you have in this format: engine/trans.....driveshaft.....pinion....(use /--\ notation for angles)

Something like: \ ----\ or \----/

get my drift?

or draw a diagram, take a picture of it and post it here.

Andrew

[dondb]

Yes i do....

Transmission yoke \ 3.5 degree's. driveshaft ---------- 0 degrees. Pinion yoke \ 1.5 degree's. Looking at the car from the Drivers side.

The best i can get out of my transmission by raising the tail end is 3.5% without hitting the tunnel.

Thanks Andrew

[icemanrd19]

Yes i do....

Transmission yoke \ 3.5 degree's. driveshaft ---------- 0 degrees. Pinion yoke \ 1.5 degree's. Looking at the car from the Drivers side.

The best i can get out of my transmission by raising the tail end is 3.5% without hitting the tunnel.

Thanks Andrew

what rear end? Lower the pinion angle which would make the driveshaft go \ instead of -----most likely by 1/2 degree . Your front working angle if that would happen would be 3.5 degrees min .5 degrees since they are both going down which is 3 degrees and moving your pinion to say 2 degrees down would make that working angle 2 degrees pinion down or like / which would cause the driveshaft and pinion to meet like this \ / causing a working angle of 2 degrees plus .5 degrees equalling 2.5 degrees.

[dondb]

12 bolt Moser, and forgot to mention...a T56 Transmission.

So I would shim the Pinion to / which would require a 3.5 degree shim, that would put my pinion / 2 degree's. That is my confusion, is the pinion considered a - or + from drivers side view currently \ ? That would clarify my mind on the opposing degree's of transmission yoke and pumpkin yoke cancelling each other out along with working angles.
Thanks for the response