Pinion angle?

[RobTwin]

Can someone confirm whether the tailshaft and pinion should be parallel to each other but offset, as shown below, or should there be a few degrees between them (approx 3°?) as I've also read?

I thought the former was correct, but having read some conflicting info, thought I'd check with the experts!

Maybe the 3° is the max angle between the drive(prop)shaft and the pinion?

[Matt]

parallel but offset, however this is under driving conditions.

This normally means setting the pinion about 2 or 3 degrees down from the trans centreline, so that if cruising at say 50mph, when the rear spring leaves are wound up a little due to driving torque, the lines become parallel.

Drag racers may set the pinion further down - this compensates for the increased spring windup under launch or acceleration torque.

[Dave999]

I'm no expert

i know just enough to be dangerous

i belive the bottom set -up to be correct

1) no more than 3 degrees for a long joint life thats line of prop to line scribed through each of motor and diff


2) and both ends need to be a close to equal as possible with the car on the floor unloaded. any variation here constantly stresses the joints

as each joint goes through a revolution is speeds up and slows down as each part of the cross passes the vertical and horizontal

for happy joints you want them doing this to the same proportion and at the same time hence the angle of the drive shaft to the parallel lines scribed in your diagram through the center of the motor and diff need to be as close as possible to the same. 1/2 a degree or better would be Fabbo

the top picture is usually unachievable without doing something well odd to you trans mount

it would work OK as pictured but the normal situation would be motor mounted more horizontal and diff facing up to it
which contravenes rule no. 2 in a big way and to varying degrees as the suspension travels

hnce you back joint might be speeding up and slowing down to a greater degree than the front stressing it and the prop 4 times per Revolution
obviously in a mopar you have an offset diff centre in the other plane as well but there is nout you can do about that without modification of housing and perhaps tunnel and definitely engine mounting

i am happy to be wrong

but i think i'm right otherwise i wouldn't have posted

Dave

[Dave999]

ah yes

matt managed it in 80% less words


hehe

dave

[RobTwin]

Thanks guys, that makes more sense, as the vibration does seem worse as the car speeds up.

Now where's my old school protractor?