Pinion angle problem or not?

[Paul G]

Pinion to driveshaft to transmission angles are supposed to be no less than 1/2 degree, and no more than 3 degrees, going from everything I have read. At ride height my drive shaft is horizontally level, 0 degrees, trans is 3 degrees downward, pinion is 3 degree upward. This should be perfect for a street car shouldn't it?

[Musicman]

To my knowledge... Engine/Transmission/pinion angle should be the same, but not in direct in alignment. Pinion should be a little lower than the tranny. I've seen a really good on-line article on the subject from AFCO or someone else, but can't seem to locate it at the moment.

Bottom line... when you step on it, the tranny tail will drop and the pinion will rise... and hopefully they will fall in direct algnment at that moment when they are under load. You also have to align them side to side too, because everything will twist as well.

OH... here we go, found the same article over at Moparts... this should clear things up for you: http://www.moparts.org/Tech/Archive/axle/8.html

Here's another: http://www.hotrodhotline.com/md/html/drive_shaft_harmonics.php

[Chryco Psycho]

pinion angle should always be nose down approx 5 -7 * from the driveshaft angle so under power the pinion will rise so the driveshaft is straight under power

[bigbluedodge]

I think you should check out the articles suggested above. They have some good diagrams to help explain what angles are and how to measure them. If I understand you correctly yours sounds wrong, but the diagrams should clear up where you should be. My Charger with CAL-TRACS is 3 degrees nose down on the rear pinion, my Barracuda with SS springs is 7 degrees nose down on the rear pinion. Good luck

[Paul G]

Confusing??   The way I read it my angles are correct in a static condition, no Load, with both the pinion and trans at opposite 3° angles, makes them parallel to each other. As soon as the drive train loads up the pinion will start to raise up and change the angles. I have found that changing the pinion angle will also change the trans to DS angle slightly. Kind of like chasing your tail. I have a set of 4° shims I picked up at the 4x4 shop a while back. A 4° shim will only get me 1° down right? The pinion is 3° up right now, pinion and tranny are parallel. With the 4° shim I will only be 1° nose down from parallel with the trans. You guys are saying I need to be 5° nose down from parallel with the tranny? If so then I would need an 8° shim?    

I have been chasing this high speed vibration for some time now. After the OD trans swap it is even more noticeable. Engine is quieter and smoother at 70, 80, 90 MPH. Now I can hear and feel the vibration even more. It will be a couple of weeks before it gets down off the jacks. I am doing some other work on it, and it's just too stinking hot out there to work on it more than a few hours on Sat & Sun mornings.  

[RallyeMike]

Pinion to driveshaft to transmission angles are supposed to be no less than 1/2 degree, and no more than 3 degrees, going from everything I have read. At ride height my drive shaft is horizontally level, 0 degrees, trans is 3 degrees downward, pinion is 3 degree upward. This should be perfect for a street car shouldn't it?

If I'm reading this right, the angles seems to be on the wrong side of the center plane of the driveshaft. As the axle loads, the angle will increase. With drive shaft at 0, the trans center line should point to above the drive shaft, and the axle center line should point to below the drive shaft. 3 degrees is good and within 1/2 degree is good too. You have to work with both angles to optimize the set up. Is there enough room with the OD to shim the trans up at he rear and then nose of the axle down? If you don't have enough room with the 518, you may have to consider if you can drop the front of the engine down (no easy solution). If you have lowered your ride height in the rear it may be adding the problem.

[Musicman]

Maybe this will help...

The picture at the top of the image illustrates a proper setup... the picture at the bottom is your current setup, see the problem?

[Paul G]

Maybe this will help...

The picture at the top of the image illustrates a proper setup... the picture at the bottom is your current setup, see the problem?

Now I see it. Thanks for that pic. I tried the 4° shims today. Ran it up to 90 mph while still on jacks. But, my ass-o-meter says it is a little better. Going to see if the 4x4 shop has steeper shims. That 4° shim gave me about 1/2° nose down now, DS to trans is about 0° now.

Can shims be stacked safely? Seems to me like they would want to squeeze right out if they are stacked? Only one of them would be in the pin.   

[Budnicks]

pinion angle should always be nose down approx 5 -7 * from the driveshaft angle so under power the pinion will rise so the driveshaft is straight under power

I agree... atleast 4* down minimum, shim it if you have to...

[Musicman]

Oy Vey... Rig for silent running... going silent...

[Nacho-RT74]

so under power the pinion will rise so the driveshaft is straight under power

Straight ? mmm, I wish will be straight under power

[flyinlow]

73 FSM says not to use shims more than 1/4 " thick in the middle where they are pinned. I assume that is so they won't slip out.

My 73 ,which  has a slightly different crossmember then your 72 has about 5* nose down pinion angle to the driveshaft with a 4* shim to help get the nose down .

With a 518 trans. there was not much adjustment room left at the transmission mount. If I remember right the 518 output shaft ended up being about 1/4" lower than the 727 and over 3 inches farther back.

Some of the luxury cars back in the day had driveshafts with a double ujoint ( they called them CV joints ?) at each end to help smoothout the ride. Those of us in Dodges and Plymouths just had to live with it. Roll down the windows and turn up the AM radio.

[Chryco Psycho]

you can drill two holes through 2 shims , tap them & insert a small set screw to keep them together
or weld them