55.2-59 Pinon angle on 56 4x4 build

[1957Napcofan]

I'm restoring a 56 Chevy 3100 and setting up the drive train angles.
Started with the engine/trans/transfer case at 3 degs. With that I had
16 degs angle on my rear driveshaft so dropped the drive train to 5 degs.
Have the transfer case yoke at 4 degs and the pinon angle the same.
This puts my driveshaft at just about 10 degs. Thinking this will cause
a vibration? Can rotate my rear axle because I have new leaf spring pads
and haven't welded them yet till I get this sorted. Should go
with a Double Cardan u-joint at the transfer case and point the pinon
at the transfer case to have zero angle at the pinon?

Stock frame 56 with a SBC 350, 700R4 trans and NP208 case. Has just single
u-joints on both ends of the rear drive shaft. Front shaft has a Double Cardan
joint at the case so front won't be a problem. Want to get this figured out before I send the frame and axle housings to the powder coaters. Need advice
from someone that knows more about this then I do.

[1project2many]

I think you'll be fine where you are. The operating angle for the top joint is five degrees and for the bottom is six. The maximum angle most books recommend is four before running into longevity issues but there are plenty of vehicles that run with more angle. I've driven vehicles with greater angles on short shafts and they felt smooth. The big key is trying to keep the rear joint operating angle in line with the front. 1 to 2 degrees of additional angle at the rear end is usually recommended so the operating angle remains good when the axle is under torque. You have one deg down now but I feel that I'd probably shoot for 2 deg based on engine size and spring design. If you're not already using them, 1330 U joints have a wider cross which gives them a larger maximum operating angle. This might be a good choice if it's not too expensive and if yokes are available.

A double Cardan is really for smoothness rather than greater angle. If you have the means to install one it won't hurt but I think you'll be fine without it. Old Buicks, Olds, and some Caddys used to run a double Cardan on the rear joint at about 3 degress with a driveshaft longer than a congressman's contact list. Those cars used four link suspensions with soft bushings and engines making plenty of torque. The double Cardan was there to provide vibration free operation under axle wrap.

[1957Napcofan]

Thanks for the reply. See you are from NH. I grew up there, moved west in 88.
How do you come up with the 6 deg running angle? I came up with 10 but
may be calculating wrong. Transfer yoke and pinon both at 4 deg, drive shaft
is 14 deg. Thought I just subtract the 4 deg from 14.

[mr48chev]

The angles at the transfer and the pinion have to match same as the angle at the trans and the pinon have to match on a two wheel drive.

I wouldn't get my head wrapped around exact numbers near as much as matching numbers as the dude who says you have to have X degrees of pinion angle is clueless to what your U joint angle is at the transfer.

On the other hand you obviously don't want excessive angles either. That will eat U joints just as bad as no angle at all.

Also the guys who tell you that you have to have the pinion angled down to compensate for torque causing the front of the pinion to rise are mouthing pure Ricky Racer nonsense. That was the unfounded theory 50 years ago and guys who try to make you think they know something still throw it out.

[1957Napcofan]

Thanks for the information. I do have my tranfer case output shaft and
pinon angle the same. Just want to get this sorted before I send the
frame to be powder coated.

[mr48chev]

If they are parallel with each other like the drawing life is good and you did good.

[1project2many]

How do you come up with the 6 deg running angle?

I misunderstood what you were saying. I thought you had 10 deg driveshaft angle after moving the engine / transmission, not a 10 degree operating angle. Moving driveshaft angle to 14 deg changes things quite a bit. At the very least you'll want to put more effort into using the 1330 joints which have a maximum operating angle of 20 degrees. 1310 joints (The "small" style used on our trucks originally) have a specified max angle of 10 degrees before binding and you're at 10 now.

Thanks for the reply. See you are from NH. I grew up there, moved west in 88.

Very cool. I moved to NH in 98. Lived in MT previously. NH is closest thing to MT that I could find on the east coast. Every other state here feels they have a right to claim a piece of you or your work. I hear Cali is worse...