Deciphering Driveline Angles

[Charlie Brown]

Drawing below shows my measured driveline angles. I went to the Spicer website and pluged in the numbers. Problem is, for me anyways, not sure how to input the correct data for the pinion. The Spicer drawing has me wondering which direction (which arrow to choose in Spicer calculator) is correct. Brain fart for sure. I either come up with operating angle "B" at 0.3 or3.3. Perhaps someone could offer their expert advice here. I'm trying to calculate how much to shim my pinion to be parallel to my trans tailshaft.

 

[steve340]

Have another read of the Spicer tips and notes. It is tricky to get your head around.
The bit to get your head around is UP or Down is always from the front to the rear of the car.
4 degrees is actually a lot. Most manufactures work on 2.5 to 3 degrees.
You could try and raise the gearbox first?
Luckily my digital protractor has a bubble on it so I can work out which end is higher and were level is. This helps me to decide if say the driveshaft tube is ascending or descending from the front to rear.
In your drawing both the trans and the diff are DOWN.
Not sure about your driveshaft.

 

[68-500]

I think the top pic is the correct figures. I don’t think your angles are to far off. When you accelerate your pinion moves up decreasing angles at both ends of the driveshaft. Are you getting vibrations from current setup?

 

[Charlie Brown]

Have another read of the Spicer tips and notes. It is tricky to get your head around.
The bit to get your head around is UP or Down is always from the front to the rear of the car.
4 degrees is actually a lot. Most manufactures work on 2.5 to 3 degrees.
You could try and raise the gearbox first?
Luckily my digital protractor has a bubble on it so I can work out which end is higher and were level is. This helps me to decide if say the driveshaft tube is ascending or descending from the front to rear.
In your drawing both the trans and the diff are DOWN.
Not sure about your driveshaft.

There's no more room to raise the gearbox without major tunnel work. If my drawing is correct, my pinion is pointing up so I'm having a hard time to wrap my head around how as you say, the diff is pointing down. I'm thinking driveline angles are more relevent than how much the trans is down - to a point of coarse.

 

[Charlie Brown]

I think the top pic is the correct figures. I don’t think your angles are to far off. When you accelerate your pinion moves up decreasing angles at both ends of the driveshaft. Are you getting vibrations from current setup?

There is a vibration in the shifter handle, although I'm not sure what to expect while driving. This is my first stick car. Is what I'm feeling "normal" for a stick car? Not sure. Should I be feeling anything at all in the shifter handle? I guess what I'm looking for is some guidence as to what is a normal feeling is, if that's even possible. At highway speeds (70 - 75), there is no vibration.

 

[RJ Squirrel]

Your drawing is wrong, if the tailshaft is 4 degrees down from level, and the pinion is 1.5 degrees up from level, then the u-joints are not at the same angle. According to this you need to raise the pinion 2.5 degrees. U-joints at different angles causes vibration.

 

[Sixpactogo]

First off. If your angle calculations are correct, you entered them wrong in the Spicer calculator. You swapped the drive shaft angle and the pinion angle which is not the real problem. The real problem is you didn't change your pinion angle to down.
Here is the correct readings. Angle 1=2.2 Angle 2=.3
IMO, I believe you need to raise your pinion angle up at least 2 degrees (maybe 2.5) to get in tolerance. Ideally your pinion angle and transmission angle should be the same. That way when your pinion moves up and down, your drive shaft angle changes with it and your numbers between angle 1 and angle 2 stay the same.
I went through this with my Charger when everyone says the pinion should be 2-5 degrees down from the transmission because of axle windup. I found that to be BS. When I installed the 6.1 and 5 speed automatic in my Charger my trans is about the same as yours. 4.2 down.
I set my pinion angle at zero thinking the axle windup would bring it in line with the transmission.
Not a chance!
After all the shimming and messing around I finally cut the perches and raised the pinion to 4 degrees nose up. All my vibrations are gone.

 

[Charlie Brown]

First off. If your angle calculations are correct, you entered them wrong in the Spicer calculator. You swapped the drive shaft angle and the pinion angle which is not the real problem. The real problem is you didn't change your pinion angle to down.
Here is the correct readings. Angle 1=2.2 Angle 2=.3
IMO, I believe you need to raise your pinion angle up at least 2 degrees (maybe 2.5) to get in tolerance. Ideally your pinion angle and transmission angle should be the same. That way when your pinion moves up and down, your drive shaft angle changes with it and your numbers between angle 1 and angle 2 stay the same.
I went through this with my Charger when everyone says the pinion should be 2-5 degrees down from the transmission because of axle windup. I found that to be BS. When I installed the 6.1 and 5 speed automatic in my Charger my trans is about the same as yours. 4.2 down.
I set my pinion angle at zero thinking the axle windup would bring it in line with the transmission.
Not a chance!
After all the shimming and messing around I finally cut the perches and raised the pinion to 4 degrees nose up. All my vibrations are gone.

View attachment 1859211

OK, this is becoming a bit more clear. I do have a set of 2.5 degree shims. When I do a visual at the driveshaft / pinion connection, there seems to be hardly any angle at all - almost straight in line, which I understand is not good for the u-joint needle bearings.

 

[Sixpactogo]

OK, this is becoming a bit more clear. I do have a set of 2.5 degree shims. When I do a visual at the driveshaft / pinion connection, there seems to be hardly any angle at all - almost straight in line, which I understand is not good for the u-joint needle bearings.

That is because it is only .3 degrees of an angle. Put those 2.5 degree shims in to tip your pinion up to 4 degrees and you will be golden. Don't worry about the driveshaft angle. It is constantly changing while you are driving anyway. As long as your Transmission is lined up with the Pinion at rest. You can't get it any better. It don't matter if your driveshaft is angled up, down or level.

 

[68-500]

Its really not rocket seince. If the trans points down 4* up want the pinion pointing up but a degree or 2 less. Then under load the pinion comes up and the two planes are nearly parallel.

 

[Sixpactogo]

Its really not rocket seince. If the trans points down 4* up want the pinion pointing up but a degree or 2 less. Then under load the pinion comes up and the two planes are nearly parallel.

That turned out to be a wives tale for me. Looks like the same story for this thread. That is about what he has now. About 2 degrees lower than the trans. I tried that exact thing and it still had a shudder when I let up. What finally worked for me was to match the pinion and trans.
That theory may work if the trans is at zero but not at -4.

 

[threewood]

You want the engine and pinion parallel under acceleration. Which means the pinion needs to be 3-4 degrees nose down from the engine angle. Quick sketch of parallel under load (top) and at rest (bottom).

According to your drawing you are right there. 2.5 degrees down from driveline angle.

 

[Sixpactogo]

You want the engine and pinion parallel under acceleration. Which means the pinion needs to be 3-4 degrees nose down from the engine angle. Quick sketch of parallel under load (top) and at rest (bottom).
View attachment 1859352

BS

 

[threewood]

BS

OK. What is BS about it?

 

[Sixpactogo]

OK. What is BS about it?

Read my post 7. Been there, tried that theory. I know that is the theory that has been around for many years and may work for some but it sure as hell didn't work for me. My pinion would never come up 7 degrees. I tried jacking up the nose on my pinion and could only get about 2.5 degrees before it started lifting the car. I have stock Mopar Performance springs. After cutting my perches twice, I finally realized that 5-7 degree difference is a bogus for a street car. Maybe ok for a drag car but what finally worked for me was matching pinion angle with the trans. My drive shaft was about .5 degrees down at rest. Under load the pinion comes up to maybe 5 or 6 degrees up but the drive shaft angle changes to something like 1 or 2 degrees up but they cancel out between angle 1 and angle 2.

 

[threewood]

The only way to know for certain how much the pinion comes up is to video it while driving and every car is different. I too am running MP SS springs and 3 degree down has worked for me on two street cars. I used 4 degree shims, no rewelding of perches. No vibrations.

 

[steve340]

A pinion may rise a degree or two under acceleration but I agree it will never rise 7 degrees - unless the springs are shot or the chassis is full of rust.
The driveshaft universal operating angles at each end need to be equal and opposite to cancel each other out.

 

[Charlie Brown]

To expand a little, while under heavy load, what should I expect to feel on the gearshift handle (TKX). Little to no vibration-smooth feeling through out the power band or will I be feeling engine / trans harmonics or other?

 

[68-500]

I don’t have experience with TKX but ive derived manual transmissions since I started driving 35 yrs. Ever single one had a vibration in the shifter if you rest your hand on it, which you shouldn’t do. If you have a vibration while cruising without your hand on it and I believe your driveline angles should work fine. Time to look at the yokes and driveshaft balance.

 

[Sixpactogo]

To expand a little, while under heavy load, what should I expect to feel on the gearshift handle (TKX). Little to no vibration-smooth feeling through out the power band or will I be feeling engine / trans harmonics or other?

If you feel a shudder or vibration under acceleration, your pinion is too high. If you feel it under deceleration, your pinion is too low.
When I set my pinion the way everyone said it should be (3-5 degrees down) to tell the truth, when I looked in my rear view mirror at 60 mph, I couldn't tell if a tractor trailer or a Volkswagon was behind me. In your case, I would expect to feel a slight tremble in your shifter but you should be able to look in your mirror and see a solid image of what is behind you. Once you get your pinion angle set properly, you will know it.