Driveshaft angle

butch27 · October 19, 2006, 11:35:13 PM

I have a '47 Ford open drive rear end hooked to a C-4 trans. The trans is angled 2 degrees down and the rear is 2 degrees up. But my driveshaft is 8 degrees uo toward the rear because of the old Ford pinion location. Will this work?

Leon · October 20, 2006, 12:15:03 AM

Your trans and diff angles are set right, they are cancelling out the accel/deaccel of the driveshaft as it rotates. As far as the 8 degrees, that might be a bit much but in your case it is probably unavoidable. Some may suggest putting the rear in a down angle but that isn't the proper way to phase a driveshaft. I've run many miles with a driveshaft like that on my T because the engine sat so low and when I took u-joints apart to inspect them, I found no problems.

enjenjo · October 20, 2006, 12:35:07 AM

It's ok as long as the included angle is not more than that. If it vibrates, you can install CV joints in it.

PeterR · October 20, 2006, 07:39:20 AM

Quote from: "butch27"I have a '47 Ford open drive rear end hooked to a C-4 trans. The trans is angled 2 degrees down and the rear is 2 degrees up. But my driveshaft is 8 degrees uo toward the rear because of the old Ford pinion location. Will this work?

In your case
engine down 2 degrees
driveshaft up 8 degrees
Uni angle = 10 degrees

This is creeping up rather high

Good guideline for maximum angle is, RPM x (UJ angle) = 16000
So with this angle you should not be running the driveshaft more than 1600 RPM.

If it is too difficult to flatten the driveshaft angle then follow enjenjo's advice of using CVs.

butch27 · October 20, 2006, 09:36:30 AM

Guys: This drive shaft is ONLY 10-1/2" long. Am I in trouble?

enjenjo · October 20, 2006, 09:43:26 AM

yes you're in trouble. The changes in angle will be too much with a driveshaft that short.

PeterR · October 20, 2006, 02:36:21 PM

Quote from: "butch27"Guys: This drive shaft is ONLY 10-1/2" long. Am I in trouble?

Well, let's have quick look to see how much trouble.

The angle a shaft changes due to a change in the axle height as the wheels pass over a bump is approximately,
Change in shaft angle = (height change) x (60/[shaft length])

In your case angle change =(height change) x (60/10.5)

And ignoring the decimal place you can see that there is almost 6 degrees angle change for each inch of vertical axle movement. A 1-inch bump in the road would take your uni angle up to:
Static uj angle 10 degrees
Bump . induced 6 degrees
Total UJ angle 16 degrees

-so you are in trouble with a capital T.

Even if the 10-degree static angle can be brought back to a more favourable 2 degrees, such a short shaft will still be a problem.

In case you are wondering how the half shafts in an independent rear cope with road undulations. For a start they are arranged with small static angle, they are almost double the length of your shaft, and being after the diff they turn about a third of drive shaft speed.

Dave · October 20, 2006, 07:43:27 PM

Quote from: "PeterR"
Quote from: "butch27"Guys: This drive shaft is ONLY 10-1/2" long. Am I in trouble?
Well, let's have quick look to see how much trouble.

The angle a shaft changes due to a change in the axle height as the wheels pass over a bump is approximately,
Change in shaft angle = (height change) x (60/[shaft length])

In your case angle change =(height change) x (60/10.5)

And ignoring the decimal place you can see that there is almost 6 degrees angle change for each inch of vertical axle movement. A 1-inch bump in the road would take your uni angle up to:
Static uj angle 10 degrees
Bump . induced 6 degrees
Total UJ angle 16 degrees

-so you are in trouble with a capital T.

Even if the 10-degree static angle can be brought back to a more favourable 2 degrees, such a short shaft will still be a problem.

In case you are wondering how the half shafts in an independent rear cope with road undulations. For a start they are arranged with small static angle, they are almost double the length of your shaft, and being after the diff they turn about a third of drive shaft speed.

Dam peter your a genius! Ive still got a vibe and a wierd noise in my coupe but i said hell with it drive it! Maybe this spring (its in storage now)
i CAN MAKE SOME MORE MEASUREMENTS AND YOU CAN TELL ME WHATS WRONG OR AT LEAST GET ME HEADED IN THE RIGHT DIRECTION. Dam caps lock! I (really this aint no bull) built 3 cars and just eyeballed the angle of the rearend and never had a vibration but now when i actually look and check it it dont work :x The coupe has a pro built frame and it came all set up and it still aint good......
Dave