Pinion Angle

[tubbedamx]

So I'm ready to weld the new perches onto the 8 3/4. The rearend is under the car and bolted in but the perches are not welded to the housing. The car is on all four tires and sitting at ride height.

Also, I don't have a driveline. All of the searches show a measurement off the driveline.

I got my protractor out and took some measurements. The tranmission is 2.5 degrees down being measured at the face of the output shaft. The rearend is 4.5 degrees to 5 degrees down too being measured on the face of the yoke.


My question is where should I put the rearend before I weld up the perches? Keeping in mind its on stock suspension, rubber bushings, low horsepower 360/auto street cruiser.

 

[fourspeed]

I believe the procedure is to put the driveshaft in, and measure the angle of the driveshaft. Then measure the angle of the rear end pinion and the pinion should be 5 degrees nose-down vs the driveshaft.

On my car, I just bolted the rear end in place with the perches "loose". Then I set the side-to-side location relative to the car body. Then I put the driveshaft in and let the car down to measure angles. Once set, we tacked the perches, remove the rear end and blazed them on.

With no drive shaft, you could wait until you have one, or you might be able to use a long 2x4 or something to simulate a driveshaft, and read the angle on it. That'd be a 2 man job though.

 

[tubbedamx]

Well I had a couple of mopar drivelines but I assumed they woudn't fit because they were from other cars. My mistake!!

So I found a driveline that fits great "Yeah" and its -4 or 4 degrees down towards the pinion.

From what i have been reading: for a street cruiser/low horsepower/leaf spring/ rubber bushings they want -2 to -2 1/2 of pinion angle.

Since my driveline is -4 would I need to put my pinion angle at +2 degrees for a total of -2???

 

[crackedback]

Right now you are about 7-7.5* down at the pinion.

The idea is parallel lines for the trans output and pinion. If trans is 2.5 down, the pinion needs to be 2.5 up to get a 0 angle.

Street car, I generally install at 5 down and be done with it. So you need to be about 2.5-3 down at the pinion.

 

[madmaximum]

That is also my understanding. You need both U-Joints to be in Opposite Flex in order to cancel the "Chug" of an Elliptical Rotation...

In lamen's terms I guess, you want the pinion gear and the output shaft to be Parallel or "the same plane". The driveshaft angle is a wash in this application. On High trucks you need to worry about that because they can bind up U-Joints at severe angles with a lot of Torque and Load.