How much of the drive shaft balancing does it have to do with vibration? I mean every big block vibrates but how much is too much? and if you suspect too much how much would balancing the drive shaft help? Then worry about pinion angle?
Say that 10 times fast lmao but seriously...
If you have a shaft that isn't balanced or off a little it can vary what and where the vibration is.
Now RRR brought up a issue of being perfect, i am kinda a perfectionist with my shafts being below the allowed run out, and even if they are 0 on run out they could use balancing, some may not need it, but you don't know unless you check.
The idea of being perfectly straight and not having to be balanced is not true as i have seen millions of times after truing, straightening shafts to perfection.
The slip yokes, weld yokes are cast and then machined and like a block can have core shift, slips and weld yokes can have the same issues.
The shafts themselves sometimes have small imperfections and may not be perfectly round and cause balancing issues.
It is rare a shaft doesn't need balancing, but when i hear a shop say "as long as the shaft was straight as an arrow, it didn't need balancing" i quickly believe they do not have a balancing machine and 8 out of 10 times im right on that.
I have learned experimenting with shaft on my machine to balance shafts to a particular area truing them to tune the shaft to take no added welded on weights.
OK
onto the Pinion angle issue made as simple as i can make it ..
Ok here we have the trans end of the shaft and angle
As you see i take the angle measurement off the joints cap, and we have 3.6 degrees
Now to the diff end
We have .6 at the Diff
We have 6.0 on the shaft
Now this is at rest as it should be, when the power is applied the diff will rotate up 4 degrees and also change the shafts angle 2 degrees and alleviate the working angle at the front under load.
At rest there is a 6.5 degree diff at the shaft, and 4 degree diff at the working ends
Underload we'll have nearly identical angles between the trans and diff, the slight lift of the housing will change the shaft angle around 1.5 to 2 degrees making it a 4 degree slope, alleviating the working angle also.
Now in cars we don't have the slope to worry about like that of a truck.
What you need to is adjust the pin at rest for the movement the diff will make, you can do 2 things with that, you can put it on a drive on lift and hold the car back and load it up and watch it and see how many degrees it moves, or you can take a jack and jack against the end yoke and see what you can move it to.
What it moves to underload is what you want to adjust for, you want to have underload no angle between the two.
Now this is for street car stuff, not performance stuff, when we add performance and the shaft speeds go beyond 5000 rpm we want 0.0 angle underload everywhere.
Joints aren't designed to oscillate at any angle really above 5000 rpms, by 5000 rpms you want to have less than 3 degrees anywhere.
This is something that has taken chassis builders a long time to understand and why cars always had vibes.
There was always misinformation about needing angles for some oscillation, for a TRUCK yes, working a large joint and heavy loads and huge tq loads, yes a working angle of some degree is important for a TRUCK.
NOT performance cars, race cars and especially BOATS, which is still a thickheaded issue with boat builders.
Most cars built today are using less and even no angles.
Hopefully that was easier to understand.
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