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Discussion Starter #1
I made a pair of guages to check my driveline angles:

2 plates 2 1/2" X 4" X 3/16" with 4 holes to bolt them onto my trans & diff yokes and a 5th hole in the center for a 29" long piece of 7/16" all-thread. Checked the all-thread for perpendicularity with a framing square.

Bolted them into place and about pooped my pants! Instead of being roughly parrallel, they made an "X". The diff end was off about 1/2", the trans end almost 1 1/2". Side to side was perfectly parrallel.

So I shimmed up the trans tail 1/2", about as much as I can for tunnel clearances, and today I'll go get some aluminum pieces of varying thickness to put between the diff and the crossmember to drop the back end of it. Then I'll start trimming the rubber front diff mount bushing.

Comments welcome & appreciated. This puppy needs to run this weekend!

John
 

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Cutting the front differential bushing should be sufficient, I wouldn't want to drop the rear of the diff too much.... pita if you ask me...

Mine was way off after my 5spd install, trans and diff were both pointing down, had to raise both. I have a poly diff mount that was easy to cut with a hacksaw :thumbsup:
 

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Just how much emphasis was placed on the end of the yolks being square to the shaft. That may have had some tolerance, since it does not matter to the end product.
 

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Discussion Starter #4
Just how much emphasis was placed on the end of the yolks being square to the shaft. That may have had some tolerance, since it does not matter to the end product.
The far end of my all-thread does not trace an arc when I spin the yokes, if that's what you mean. They are true to the axis of the yoke shaft.
 

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Discussion Starter #6
My Bad,
Do you feel the crossmember or diff cover may be getting overstressed by changing the angle of the differential from it's as-built specs?
 

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If your shimming the rear end or tranny to get them in line as oposed to just pulling it over and bolting it down there should not be any extra stress put on either unit, right?
 

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A few questions about changing al this around....

what are the affects of loading on acceleration to said alignments...

what are the affects of unloading and hitting the brakes....

how close were the specs for any typical chassis in construction??

how critical are any of these specs to final operation in a PRACTICAL sense??

isn't it easier to just jack up the car on stand, or better yet a chassis dyno, and stick fingers on the tranny output shaft, and diffy input to feel for crappy vibrations??

IMO, it SEEMS more complex than what being discussed so far...NO??

:crazy: :thud: :WTF :cheers:
 

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Discussion Starter #9 (Edited)
sixfooter,

I need to change the angle of the diff to several degrees up in front which will be putting a twist on the crossmember, regardless of any shimming. (I don't have the ability to machine a tapered shim in my garage)
 

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Discussion Starter #10
mrvette, I'm just trying to get closer to optimum than the assembly line set it up. I have always had a vibration at certain RPMs which felt like it was coming from the rear end area. As far as changes due to accel/decceleration, it will be no more than it ever was, but the overall stresses on the u-joints & driveline should be greatly reduced for smoother easier running. `U-joints are not constant velocity joints, their speed around the circumference they trace varies because they actually travel in an oval, not a circle. This is why it's important to have the ends offset but parrallel so the variations cancel each other out.

Besides it's fun to figure out & fix stuff like this! :partyon:

http://www.drivetrain.com/driveline_angle_problem.html
 
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