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Discussion Starter #1
Hello!

Does the 1gen have driveshaft U-joint angles in two planes?
I mean both the "looking from the side" angle and also "looking from above" angle?

I used a cross-laser and two plumb bobs (one in damper, other in gearbox pinion). I lined the laser across line to the rear alignment master holes and adjusted the subframe so that the plumb bobs line up with the longitudal laser line.
The engine+tranny is now aligned but way off to the driver side, so much that I cannot get it centered to the tunnel. And I cannot move the rear axle to line up with the tranny because it would be hitting the exhaust. So it seems I have to have the engine+gearbox offset to the rearend pinion aka U-joint horizontal plane angles.

Do people have their engine+tranny centered in the tunnel and in line with the rearend or not?


Laser longitunal beam lined up with the damper and tranny pinion plumb bob. Cross beam lined up with rear alignment master holes (near the leaf spring front eyes)


Engine+tranny offset to the driver side


Appreciate any info!

Best regards,
Pasi
 

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Alignment of the driveshaft doesnt have to be perfect. If you get to angles of 8 degrees or more, then you will have vibrations.
If your driveshaft has zero angle, it is actually bad, the needle bearings won't turn enough to spread the grease and will not last as long.
 

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By the pictures shown, very nice BTW, rear axle being off by 1/4 inch makes for a horizontal angle of 0.05° - insurmountable.
As Mr. Pozzi states, keep the vertical angles, those viewed from the side, closer to 3°-5°.
 

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Discussion Starter #4
Appreciate the help!

My diagonal measurements from leafspring perch alignment bolts to lower A-arm ball joint grease fittings are now within 0.08" and the diagonals from rear master gauge holes to subframe front master gauge holes within 0.04" of the factory specs :D
Pretty interesting considering that now the subframe front master gauge holes don't line up at all with the body holes above...

Now it's off to dropping the rear end somewhere in the middle, checking the pinion angles and tacking the spring perches. Then it's off to narrowing the driverside axle tube and widening the passenger side axle tube (yep it's a Mopar 8 3/4 rearend with the pinion offset more than GM...blasphemy I know). Have to compensate that by making unequal-length axle tubes.

BR,
Pasi
 

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Only the BBC has a horizontal offset because the motor is offset. The vertical angle is he same for all other GM cars vertically. As Dave Pozzi stated above you strive for an angle of ±3° degrees. More so (max of 5°) if you are building a high torque engine as you will break parts as well as get a vibration above 8° degrees (that requires a constant velocity joint instead of a U-joint).

Wikipedia has an excellent write up on what is happening as a drive shaft rotates once the universal accelerates and decelerates twice.

https://en.wikipedia.org/wiki/Universal_joint

Big Dave
 

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If using a Mopar rear axle, I would leave rear axle as OEM configured, and follow Dave's Wiki suggestion.
Center the axle flanges within the wheel houses on both sides.
Good measurements and I would agree subframe be off from firewall as design, drafting, cutting/shaping parts, assembly, was all done on drawing tables using rulers an assembly line with tape measures.
 

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On 1970 Camaros, the pinion is offset 3/4" to the passenger side.
I had a Camaro with 9 degrees angle and it rattled all the gears inside the transmission at 60 mph.
 

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Discussion Starter #8
After some measuring my drivetrain angles are in the attached pic at ride height (leaf springs on jack stands). Currently using a stock tranny mount, changing to ES tranny mount will lift the tranny a bit (if using the supplied plate between tranny and the mount).

I have the axle leaf spring perches still loose so I can still do whatever I want with the rear end alignment and pinion angle.

Everett#2390 : The 8 3/4 rear end I have is a bit too narrow so I have to widen it to make my 265/40/18 tires fit perfectly...Here we have a stupid law prohibiting the use of wheel spacers

Larger Dave : Appreciate the link but I'm pretty aware of the nature of U-joints, the acceleration/deceleration cycling and it's limitations. Obviously a CV joint would be an improvement but hell, we have managed with the U-joint forever :wink2:

BR,
Pasi

 

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Wrong pinion angle You have three degrees down but four degrees also down at the transmission. The angle is acceptable but not the orientation. The pinion points up and the tranny points down.



Big Dave
 

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I have found that the easiest way to see/understand pinion angles is to draw the engine/driveshaft/pinion on a piece of paper with the angles that you have measured, then rotate the paper so the driveshaft is at 0 degrees.

Viually it is easier (for me anyways) to see equal and opposite angles that way.

Larger Dave's example:


Paper rotated so driveshaft is at 0 degrees:
 

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Discussion Starter #11
Wrong pinion angle You have three degrees down but four degrees also down at the transmission. The angle is acceptable but not the orientation. The pinion points up and the tranny points down.

Big Dave
Yep I know that they are wrong now, I just wanted to get a baseline where my tranny angle is vs. driveshaft ATM.

BTW : How many of you have the tranny more down than the driveshaft?

Thanks!

BR,
Pasi
 

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I have never had or seen a car with the tranny pointing down relative to the driveshaft.

Always see the engine level and the DS angled down to the rear end.
 

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Discussion Starter #13
Here's a nice video showing the difference between the "ideal world where angles are static" vs the very dynamic real world. Of course with a manual trans in the video the pinion angle effect is even more evident :
 

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Great video, thanks for posting! Sure makes one think about some CalTracs or a 4 link setup to control that. Wonder how much the angle changes under steady throttle relative to standing stationary.
 
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