Drive shaft angles, your thoughts please

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Drive shaft angles, your thoughts please

Post by predator » Wed Mar 16, 2016 10:10 pm

O-k, I have a couple of questions. I want to ask about a problem I'm having with my 71 Plymouth B-Body Road-Runner. See, I have the Engine sitting in the Car bolted up the the Transmission. I have the Engine sitting upon the Motor-Plate in front. The Motor-Plate is not attached yet to the Frame Rails. I have this problem though. I need to lower the Engine in order to run the Air-Grabber hood. I need to lower the engine about 3 inches. Well what has me concerned is. I am worrying about ending up with a change in the Pinion Angle. QUESTION: should my pinion angles be the same between the front ofthe Drive-Shaft, and the rear of the Drive-Shaft?

I recall years ago that I read an article regarding this subject. That in the article, it said something about needing these two angles being the same. I recall how this article saying something about when one U-Joint is accelerating, you want the other decelerating. Or something like what I just wrote.

I really need to get-up to speed regarding how I set-Up my Drive-Line. So any thoughts that any of you might be able to give me will be appreciated.

Good-By Chris

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Re: Drive shaft angles, your thoughts please

Post by peejay » Wed Mar 16, 2016 10:40 pm

The U-joint angles need to be the same relative to the driveshaft.

The EASIEST way to do this is to have the pinion and trans at the same angle, so say if the trans is 2 degrees nose-up then the pinion needs to be 2 degrees nose-up.

This is not always possible depending on floor clearance or drivetrain angle or other things so sometimes you have to go to a complementary angle, so you need to factor in how the driveshaft sits in the chassis. So say you have a SBC swapped into an old Studebaker and the only way to make it fit was to stuff it 10 degrees nose up. If the driveshaft sits in the chassis 5 degrees nose up then that is a 5 degree angle on the U-joint, so you would want to make the pinon 0 degrees for a 5 degree angle at the rear U-joint. (Numbers pulled out of my ass but this is something I had to do a few years back... and moving the pinion angle will also change the driveshaft angle so you have to home-in on it)

The pinion should be slightly down relative to "perfect" in the case of leaf sprung cars to compensate for the springs' flexing around when under power, too.

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