You don't need to do anything fancy. You don't even have to remove the driveline and car should be on the ground or positioned as such.
Fact is the shaft can't be measured with it out of the car.
Here's a couple links to a good articles explaining it all.
With all due respect, Not really.
DRIVE LINE PHASING[/quote]
I've worked with drivelines and drive shafts on my cars, fleet trucks and installed equipment and the above artical left me scratching my head. The author was going back and forth between cars and trucks which are the same but different, and doesn't explain relationships, etc.
Take the following illustration:
Wrong is
Right for a
leaf sprung vehicle in motion at "speed", speed being ? 30-40-50-60 mph? and above ?
THe author does write this:
Normally the pinion gear angle is a negative angle and the nose of the rear end is pointed down. This allows for the upward movement of the rear end when torque is applied. Those who follow racing will know the term spring wrap. Setting up a drive line for racing situations or high torque off-roading is different and much more complicated than for street vehicles, as many more variables enter into the formula.
A Story:
When I was a kid I had the rear axle of the '71 on stands and spun up the drive line like we do when we're kids. I noticed there was a vibration ~ 40? (this was a long,
long time ago). So I watched under the car while playing with the throttle. (Speeds are for purpose of illustration only)
At low speed there was no vibration, then as I gradually increased speed there started a vibration. In looking at the chunk I saw it was getting a little blurry. Continuing to gradually increase speed the rear yoke would pop up - no vibration- drop down - vibration - pop up - no vibration - and so on. Increasing speed a bit more the rear yoke popped up and stayed up and didn't vibrate.
Apparently the physics of the spinning drive shaft created forces about the rear yoke resulting in the rotation of axle to a point the physics of the drive shaft locked the axle in position, apparently where the system was going through a minimum change in velocity. The minimum change of velocity is when the system is in as straight of line it can get.
In my observation it was only the physics of the drive shaft causing the change of angle of the pinion. In operation there is hte "torquing" of the axle and climb of hte pinion from "pushing" the car.
So in the above illustration
wrong is
right for a vehicle in motion, the physics involved "lifting" the pinion till the system in in a straight line.
At least this is the way it is suppose to work in a leaf sprung automobile!!!!
Also, in the above illustration, both pictures are the same. In both pictures the driver (engine and trans) and driven (pinion) lie in the same plane so rotating the axle will take both systems out of phase.
Phase, I forgot to address that, sorry. In a U-Joint system there are two acceleration and decelerations per rotation (unless both driver and driven are in a straight line). So now you have a joint on each end of a shaft and when the driver is accelerating the shaft the driven is decelerating the shaft keeping a constant velocity.
I didn't want to get into any of this .....
When I forst looked at the illustration on this site I thought Madness , shear MADNESS!!! The shaft will rotate into knuckle city.
Then I realized it was a toy car site. And their using heims. Heim joints don't allow the axle to rotate so the driver and driven have to be set in the same plane.
Then tere is factory 4 link (sic) and the bushings allow a little play.
Leaf springs? Axle wrap is our nightmare.
I'll re read this and see where I forgot this or that, where something could have been written better ... it's not a term paper.
Conclusion ...
Leaf sprung automobile drivelines are designed so the rear axle rotates into a straight line thus everything is in phase and everything is spinning at a constant velocity resulting in a nice cushy ride.
Truck drivelines, otoh, such as my Toyota 4x4, will never be in a straight line, the system is designed for the axle to rotate (sort of,) into phase. The truck will
always have
some vibration because the drive shaft will always have two accel/decel cycles per revolution.
Continued later .....
Also wanted to add-
Check the torque on the pinion nut on your 3rd member (rear axle pinion @ the yoke)
I've been finding 9" fords fromt he late 60s and 70s have been working the nuts loose causing the pinion yoke to slide forward and become loose causing occasional vibrations and quick destruction of the rear u-joints. I have yet to run into a case with the 8" rear but have found at least 4 different cases with the 9" rear, mostly in trucks.
And heres a funny thing.
Shortly after buying the Toyots the rear pinion seal started leaking. I had it fixed (Warranty) and when I got the truck back it had a vibration. WTF? Of course the dealer couldn't feel it ... WTF?
As time went on, a couple 10k miles or so, the vibration got worse and locking in the front hubs would turn the truck into a vibrator.
They traced the initial vibration to the Tech having over-torqued the rear pinion nut (which took out the bearings making the vibration worse).
Wow, an overtorqued pinion nut causing vibration... learned something new.