Pinion angle and drive train alignment

[z0sick]

Need a little help here setting up car. There is a lot of information out there and some of it contradicts others. Here is what I have:



Engine/Trans is at 4* tail shaft down...


Drive shaft is perfectly 0*...


Pinion is at 6.5* down...


Some sources say to only use the drive shaft and pinion while others say to throw the drive shaft out all together and use the tail shaft and pinion only. My opinion is that the tail shaft and pinion should be equal and opposite for a street driven car. (meaning that my tail shaft is pretty much fixed, so I need to angle the pinion UP 4*) this would put the center line of each parallel to one another. To me, this would reduce the vibration induced by the offset angles.

The other theory is that the drive shaft and pinion should have a -3* angle no matter the engine/trans angle.


What say you?

[dontlifttoshift]

My opinion is that the tail shaft and pinion should be equal and opposite for a street driven car. (meaning that my tail shaft is pretty much fixed, so I need to angle the pinion UP 4*) this would put the center line of each parallel to one another. To me, this would reduce the vibration induced by the offset angles.

You already know the answer. You can get away with as much as a degree or two downward on the pinion if you want, depending on suspension type and bushing material but with a heim joint four link parallel would be good.

[z0sick]

You already know the answer. You can get away with as much as a degree or two downward on the pinion if you want, depending on suspension type and bushing material but with a heim joint four link parallel would be good.

A degree or two downward from parallel, or from the 0* (horizontal with ground)?

[dontlifttoshift]

a degree or two from parallel is what I meant. this really applies mostly to leaf sprung rear ends and somewhat to link type suspension with large rubber bushings.

[BMR Tech]

If at all possible both u-joints should be at the same angle or as close as you can get them. Depending on the configuration of your trans crossmember, sometimes you can shim the trans mount or trans crossmember if you need to alter the front angle. For the rear we generally recommend that our customers run no more than 2-3 degrees for street applications. 6 is definitely too much angle and will make your u-joints hate you...

[z0sick]

If at all possible both u-joints should be at the same angle or as close as you can get them. Depending on the configuration of your trans crossmember, sometimes you can shim the trans mount or trans crossmember if you need to alter the front angle. For the rear we generally recommend that our customers run no more than 2-3 degrees for street applications. 6 is definitely too much angle and will make your u-joints hate you...

Thanks for the help. I'll try to shim the trans mount up to get the motor/trans between 2-3* down (from horizontal) and rotate the pinion to 1-2* up (from horizontal). This should put them almost perfectly aligned under heavy load and only off by 1-2* at rest.

[imcarfan2]

Not to hijack this thread, but along the same lines, I'm going to be putting a 200-4r trans in a car that didn't originally have one (had a TF727), so I'll be modding the crossmember and deciding my own angles. Am I shooting for a particular number for the tailshaft, like 2-3* down? And the same thing for the axle, but 2-3* up? I had heard someone say 5* and 5*, but I have no clue.

Again, sorry if I hijacked.

[exwestracer]

May just be an optical delusion, but the driveshaft looks pretty much parallel to the rocker pinch weld in the second photo, but not at all parallel in the last photo. Did your rear suspension height change when you were measuring the angles?

With that short of an instant center on your 4 link, you are going to get a lot of pinion angle change with travel and possibly a lot of anti-squat effect as well(?). I agree that the pinion and trans shaft should be parallel, but keep in mind what the pinion is going to do during acceleration AND coast (assuming a manual trans...)

[z0sick]

May just be an optical delusion, but the driveshaft looks pretty much parallel to the rocker pinch weld in the second photo, but not at all parallel in the last photo. Did your rear suspension height change when you were measuring the angles?

With that short of an instant center on your 4 link, you are going to get a lot of pinion angle change with travel and possibly a lot of anti-squat effect as well(?). I agree that the pinion and trans shaft should be parallel, but keep in mind what the pinion is going to do during acceleration AND coast (assuming a manual trans...)

The car is/was sitting on all four corners with entire weight on it. No change in height between the pics. It does have a manual (TKO 600). The pinion will nose up on acceleration and down on coast, right?

[exwestracer]

The car is/was sitting on all four corners with entire weight on it. No change in height between the pics. It does have a manual (TKO 600). The pinion will nose up on acceleration and down on coast, right?

Correct. With the stick, you will have a lot of downward pinion rotation force on coast, especially in the lower gears.