[dv657172]

65 GTO w/68 400 and TH400
100% dedicated drag car

Engine angle is 4.5 degrees (downward) at harmonic balancer and confirmed at tailhousing shaft

Driveshaft angle is 2.8 degrees (downward)

This equates to a 1.7 degree working angle and I keep reading that the preferred angle is 0 to 0.5 degree.

Would you shim the transmission mount to reduce engine angle and get it more in line with driveshaft?

If so what thickness roughly?

[johnta1]

You also need the rear end angle?


The 1.5 angle is probably good at 6500 RPM? (guess on my part)

What RPM do you run?

[dv657172]

Not sure why you need to know the pinion angle which is 1.2 degrees downward sloping. RPM is 5500 to possibly 6000. New to all the suspension and driveline modifications but trying to learn.

The pinion angle is set based on the driveshaft angle which should be inline with the engine (i.e. crank angle) and by what type of bushings are being used in the control arms, right?

Also there seems to be a lot of confusion over the pinion angle of the rear end vs. total universal joint working angle at the pinion

I am trying to figure out if the engine angle is too steep relative to the driveshaft because it seems most "experts" say it should be 0 to 0.5 degrees.

I dont know, thats why I am asking. Trying to learn and figured you guys have the experience.

[johnta1]

The pinion angle is set based on the driveshaft angle which should be inline with the engine (i.e. crank angle) and by what type of bushings are being used in the control arms, right?

No. The pinion angle is based on the rear end only. The rear can be pointing up or down, which also affects the ujoint angle at the rear end. The 2 ujoint angles is what you need.

[Mean Green]

People always disagree on the proper way to set pinion angle.

I have my engine set at 1.6 degrees down towards the rear end.

I have my rear end set at 0 degrees. So my pinion angle is 1.6 degrees.

Under acceleration the pinion raises between 1 and 2 degrees.

Let's say the pinion raises 1.6 degrees. That puts the pinion in a direct line with the transmission tail shaft/crankshaft.

This is with a 4 link car with solid heim joints. I set my ladder bar car with solid heim joints up the same way.

[dv657172]

Johntal1 - I guess I would prefer to have as close to zero working angle between the engine and front of the driveshaft and a resting negative pinion working angle of -2 to -2.5 degrees so that under a load everything is in alignment.

Mean Green - I agree with that. My front working angle seems too high? Engine at 4.5 degrees and driveshaft at 2.8 degrees, would you adjust to get them more in line?

[DCVING]

Originally Posted by dv657172

Johntal1 - I guess I would prefer to have as close to zero working angle between the engine and front of the driveshaft and a resting negative pinion working angle of -2 to -2.5 degrees so that under a load everything is in alignment.

Mean Green - I agree with that. My front working angle seems too high? Engine at 4.5 degrees and driveshaft at 2.8 degrees, would you adjust to get them more in line?

"DV"

A lot has to do with how much room you have for adjustment. Some cars dont have adequate room to shim the engine and or transmission to get the crank and front u-joint close to 0*. You want the engine setback angle anywhere from 1-5 degrees in my opinion. Then set your rear end angle till you obtain no more than 3 degrees of pinion angle. Depending on your suspension setup and what type of bushings your running will change what your working angle will be. make sure you make your adjustmants with the car the way it sits at the starting line. Fuel/driver/helmet jacket and pants etc etc. From you OP I think your setup pretty good. You might need to bring the rear up a degree but Id leave well enough alone, that is unless your killing joints.

[johnta1]

You want the engine plane and the rear end plane to be the same. Without the rear plane angle you have no idea what the angle is.
If you rear end angle is down and the engine angle is pointing down the same amount is what you want. (figured from front to rear)
Then if one or the other is too much then adjust the opposite to get to what the other is.


In Mean Green's case he knows what the rear end is and how much it changes. (I'm surprised the rear rotates that much under load)

[Keith Seymore]

There are two u joints in the shaft, each generating accelerations and decelerations as they rotate (two kicks per rev of the shaft).

The u joint working angles at each end need to be equal and opposite in order for those forces to cancel out.

K

[Keith Seymore]

Originally Posted by Keith Seymore

There are two u joints in the shaft, each generating accelerations and decelerations as they rotate (two kicks per rev of the shaft).

The u joint working angles at each end need to be equal and opposite in order for those forces to cancel out.

K

Additionally, the u joints don't care about the orientation of the individual components or the frame or the ground: only the difference between the two.

The vehicle could be on its side and the u joint working angles would be the same*.

K

*barring any changes in suspension compression, of course.

K

[johnta1]

You want the engine plane and the rear end plane to be the same.

That was supposed to be in parallel. The same angles.
If there is a left or right (as looking from top instead of side) angle difference that is also another can of worms. (like front axle on 4 wheel drive, leave that for Keith)

[dv657172]

Thks for the opinion DCVING, I am assuming about a 2 degree rise in the pinion under load with slicks and polyurethane bushings in the upper control arms while the lowers are stock for now.

Just to be clear when you said 3 degrees on the pinion you were referring to the working angle correct? (driveshaft + rear pinion)...which is currently at 4 degrees (2.8 + 1.2, both downhill)

[AG]

The driveshaft angle does not matter, it's the angle of the rear of the trans and the angle of the pinion on the rear like mean green said, measure and add together. I have my pinion angle 2 degrees down with a Caltrac rear suspension and works well.

[dv657172]

I appreciate all the thoughts and comments and while my question was basically about the large working angle at the front u-joint I appreciate the discussion and thoughts on pinion angle.

To be honest, I am not sure what to do with my angles. While they seem to work fine, I want to set them to be at the optimal level.

In the cars first outing many years ago with stock/orginal upper and lower control arms & a new 9" Moser rear, the driveshaft pulled out at about 1,000 feet and car went for a spin but no damage. After that the upper control arms were replaced (Hotchkiss double adjustable) and the shop set the pinion at what they said was -2.5 degrees. Fast forward to today (but only about 20 runs later on the car) and my interest in learning/doing everything I can myself, I have measured the following:

My engine angle is 4.6 degrees downward
My pinion angle is 1.2 degrees downward
Polyurethane bushing in adjustable UC arms, rubber in stock LC arms
I am assuming a 2 to 2.5 degree reduction in the angle of the pinion under load

Would you change anything?
I appreciate DCVING previous input on setup

[DCVING]

Originally Posted by dv657172

I appreciate all the thoughts and comments and while my question was basically about the large working angle at the front u-joint I appreciate the discussion and thoughts on pinion angle.

To be honest, I am not sure what to do with my angles. While they seem to work fine, I want to set them to be at the optimal level.

In the cars first outing many years ago with stock/orginal upper and lower control arms & a new 9" Moser rear, the driveshaft pulled out at about 1,000 feet and car went for a spin but no damage. After that the upper control arms were replaced (Hotchkiss double adjustable) and the shop set the pinion at what they said was -2.5 degrees. Fast forward to today (but only about 20 runs later on the car) and my interest in learning/doing everything I can myself, I have measured the following:

My engine angle is 4.6 degrees downward
My pinion angle is 1.2 degrees downward
Polyurethane bushing in adjustable UC arms, rubber in stock LC arms
I am assuming a 2 to 2.5 degree reduction in the angle of the pinion under load

Would you change anything?
I appreciate DCVING previous input on setup

Get rid of them lower arms with rubber bushings. Start there my friend. Secondly make sure you have a proper length and diameter driveshaft. Lastly don’t over complicate your brain with angles. Just make sure your pinion is down 1-2 degrees.

[bluegoat65]

The objective is to have both pinion angles parallel to each other under load and keeping the driveshaft center line as close as possible to centered to them. Perfect Example would be the chassis level, the trans tail at dead zero, the driveshaft level and the pinion at zero. Lets say the example here is a ladder bar car. Now adjust the pinion down 2 degrees, so on the hit, the bars will rotate up that 2 degrees and will put the drive line back centered and in perfect harmony. 4.5 degrees down angle at the trans is a ridiculous amount to even get close to getting the pinions correctly parallel. With that amount the pinion needs to be at 2 to 2.5 degrees up angle and on the hit it will roll up to the 4.5 degrees to get back to parallel. With that, the driveshaft is all sorts of out of center with the pinions. This will cause bad vibes and breakage and possible injury to you and car. Rossler transmissions has a good diagram on their site as to proper setup. hope this helped. Peace!

[dv657172]

Bluegoat65

The large downward angle is what started my original post to begin with. I have watched a ton of videos (the best being KevinWilsonSBC utube IMO), read every post and comment I can find on the topic. I understand the concept and the goal of having the driveline parallel under load, I am trying to figure out how to get there. Thats why my original post was whether I should shim under the tailshaft?

[bluegoat65]

Yes that is what I am saying. Start there and work back. Just remember to level the chassis. Don t make adjustments with the car on its wheels or ride height. Kevin Wilson is a great go to. He will even help you if you reach out.

[Scarebird]

You don't need to level the chassis - any component measurement taken will all have the common denominator of chassis angle.

It is best to have the axle at ride height. I had a 2 post lift and used an axle stand (5 foot tall adjustable jackstand) to lift the axle to ride height.

Then measure engine/trans, shaft, diff and calculate what needs to do what.

[dv657172]

Thanks guy for the replies, I hope I didnt sound like I was ranting before