Another Rear Pinon Question...

[Torkman66]

You guys are probably sick of rear pinon questions, and I have been the source of a lot of them...apologies up front.
Anybody who follows these threads knows I worked a lot in the past setting up the rear angle (yes James, not done correctly by rewelding perches) by adding a shim.
New Tom Woods DS, new u-joints, rebuilt gears (4:11), all new rear bearing, axles, Torsion bars for axle wrap, etc.
I now have the rear DS at 18.8 degrees and the pinon at 17.5 degrees using a 4-degree shim. That gives me an operating angle of 1.3 degrees.
But...I am getting a cyclical vibration during steady cruise (above 50 mph or so) and during acceleration, but not during deceleration.
My analysis:
1. I need a couple more degrees of working angle (I do not think this is right because it currently falls perfectly between 1 and 2 degrees)
2. It is actually in the rear end gear set. (This might be the case but in prior cases of this the noise was heard at nearly all speeds)
3. It is maybe a wheel bearing (New bearings and I think this would be heard in all conditions)

Thoughts?

 

[DirtDonk]

Yes, less likely to be the wheel bearings, I think. Possible, but less likely than other things.

Interesting about the acceleration/deceleration vibration. Pinion angle is pointed below the center line of the driveshaft. Correct? Not above it?
I think I asked that in one of your other threads, and you said down. But had to double check.

 

[Torkman66]

Yes. Down. I did get a suggestion to take out the 4 degrees and replace with 2.5 degree shims. That would move pinon from 1.5 to 3. Maybe with the softer spring back (removed three leaves to lower) even with the traction bars it is riding too high during acceleration and making it vibrate a bit. I sure could give that a try and see.

 

[DirtDonk]

I know my geometry, she’s not so good. But you are putting the thin edge of the shim towards the front, correct?
Or do you need to reverse them on yours?
I’m just thinking that taking it out one and a half degrees, should raise your pinion up to zero. Not down to three.
Or is my geometry backwards as usual?

 

[Oldtimer]

Pull the rear driveshaft, and drive with front axle. That would eliminate rear driveshaft as source of vibration.

 

[Torkman66]

@DirtDonk Yes, you are thinking about it backwards. The shims raise the pinon as long as thick portion of shim is in back, thin in front. Mine was at about 5.5 down before any shim and I put in 4-degree shim to raise pinon to 1.5 (attempting to get it between 1 and 2). But given my weaker leaf stack and associated axle wrap I'll take out the 4 degree and replace it with a 2.5 degree...essentially lowering the pinon 1.5 degrees for a 3-degree working angle. Or put another way...I have 5.5 degrees down with no shim ( 4 degree removed) and if I put in a 2.5 degree shim it will raise pinon to a working angle of 3. Clear as mud!