Picked up and installed a new CV driveshaft/yoke for the rear, and a new longer front driveshaft yesterday:
The existing/stock front driveshaft might have been OK, but it only had like 1" more outward travel, better safe then sorry. The front driveshaft was made with same size tubing as the rear shaft, so slightly larger OD then a stock shaft. No clearance problems on this applications (258/T5/Dana 300/2.5" lift).
With the rear shaft, you have to change the Dana 300 yoke from the stock non-CV type to the CV type.
I flipped around the 4" shims I installed on the rear leaf springs (fat end toward front now), just to see if this would get me close.
My angles now:
10-11 degrees UP on the pinion
12-13 degrees DOWN on the driveshaft
So, the pinion is running 1-3 degrees DOWN from the driveshaft, 1 degree preferred. It is hard to make out the exact degree with my angle finder, but I am going to guess it is closer to a 2-3 DOWN angle.
Test drive confirmed the angle is still not correct. The vibration doesn't start now until around 65 MPH, so I am getting closer. I will swap in some 6 degree shims next, see what I get.
I am measuring the pinion u-joint angle on an actual u-joint cap. The rear end housing/yoke do not have a machined surface that runs the exact same angle as the u-joint. Bit of a pain, but the most accurate way to measure the pinion u-joint angle
I can also tell by looking that I have a bit more then the recommended 1 degree downward angle. With a one degree difference, the pinion yoke/driveshaft yoke would almost be parallel, and they are not.
Hopefully the 6 degree shims get it right
A quick not about the shims - you can't necessarily go by what they are advertised as. An example:
Pinion angle, no shims - 9 degrees UP
Pinion angle, 4 degree shim, fat end to back - 5 degrees UP (9-4=5) WORKS OUT
Pinion angle, 4 degree shim, fat end to front - 10-11 degrees UP (9+4=13) DOESN'T WORK OUT
Also, when you change the pinion angle, you change the driveshaft angle some, too.
My driveshaft angle was at 15 degrees, with the pinion UP 5 degrees
My driveshaft angle is now 12-13 degrees with the pinion UP 10-11 degrees (CV shaft)
I am "scared" a 6 degree shim is going to make the pinion u-joint angle match perfectly with the driveshaft angle
That would be perfect with a linked rear end, but with leaf springs, you want the pinion a degree down to compensate for slight axle wind up. Or so they say......................
On my red Scrambler, with a CV shaft, I have zero vibration. I need to check the angles on it, and match
On my Tan Scrambler, with a CV shaft, slight vibration at exactly 60 MPH only, slower or faster then exact 60, no vibration.
IF I some how end up with the pinion u-joint/driveshaft angle exactly equal, I will probably slightly lift the engine/transmission to give it a slight misalignment. Lifting the power train will increase the driveshaft angle.
The vibration I have is slight, not super bad, just aggravating. Mainly feel it in the seat/floor boards, not audible. I know it should be running super smooth, so i will keep working at it.
That't it for now