Driveshaft phasing

[William McCormick]

Both ends of the 4' long Yokes are aligned. Can't change that without cutting & welding. 3' section I've tried both phased the same & 90 degree. I can't say which is better. My theory is the front & rear joints have very little angularity, I think a few degrees. There wouldn't be much oscillation at this angle. Not sure how to measure the trans & differential angle precisely, to my eye, they are very close to matched.

Are the motor or transmission mounts going? That can cause weird stuff under a load.


Sincerely,

William McCormick

[Willie B]

Are the motor or transmission mounts going? That can cause weird stuff under a load.


Sincerely,

William McCormick

They look good. That was an early suggestion, checked a while ago. I've been using it several trips over the weekend, I can't help feeling it behaves like a driveshaft issue. I still haven't found time to replace two of the three U joints. I've tried swiveling on the spline with little change.

[William McCormick]

They look good. That was an early suggestion, checked a while ago. I've been using it several trips over the weekend, I can't help feeling it behaves like a driveshaft issue. I still haven't found time to replace two of the three U joints. I've tried swiveling on the spline with little change.

Sometimes you have to get in there with a breaker bar test them under a load and check them out. I had that happen once, I was afraid to put any more pressure on them with a bar, I couldn't figure out what it was. Finally, a young kid put it up on the lift with me in the truck and I braked and goosed it at the same time and he said "motor mounts" that fixed it. It caused the truck to shimmy and shake. And it also caused some exhaust sounds every now and then. I truly hope you find out what it is. I know how much I hate mystery **** in a six or ten thousand pound bullet.

Sincerely,

William McCormick

[William McCormick]

They look good. That was an early suggestion, checked a while ago. I've been using it several trips over the weekend, I can't help feeling it behaves like a driveshaft issue. I still haven't found time to replace two of the three U joints. I've tried swiveling on the spline with little change.

I always change the universals, you don't want to go pole vaulting.

Sincerely,

William McCormick.

[Willie B]

Sometimes you have to get in there with a breaker bar test them under a load and check them out. I had that happen once, I was afraid to put any more pressure on them with a bar, I couldn't figure out what it was. Finally, a young kid put it up on the lift with me in the truck and I braked and goosed it at the same time and he said "motor mounts" that fixed it. It caused the truck to shimmy and shake. And it also caused some exhaust sounds every now and then. I truly hope you find out what it is. I know how much I hate mystery **** in a six or ten thousand pound bullet.

Sincerely,

William McCormick

28,000Lb bullet.

[lars66]

Are you sure the rear end is inline with the rest of the truck?

[Willie B]

Are you sure the rear end is inline with the rest of the truck?

Are you referring to wheel alignment? Rear wheels perpendicular to frame, and centered behind front?

[lars66]

No, I am reffering to is the rear end housing on plane with the front axel and centered with the front axel.

[Willie B]

Yes, and yes. The rear axle was moved forward a bit. Several rechecks have been performed to ensure no errors were made. With only minor deviation all is parallel, centered, and aligned.

Based on my measure, the transmission output is within a degree of parallel with the differential pinion. It is a truck, it doesn't turn at high speed, but every angle to be considered is parallel, or very close. Tires & wheels have been balanced & checked for run out, sideways & radius. No explanation for the shake.

[farmersammm]

No, I am reffering to is the rear end housing on plane with the front axel and centered with the front axel.

Yeah, I see where you're going. If the pinion yoke is pointing anywhere from absolute parallel to the frame, you have misalignment. Up and down variances are a different matter. But, even that can cause problems..........think about the kids that lift their jeeps 24" without changing the pinion angle..........mondo problems.

[farmersammm]

As far as driveshaft speeds.............a truck doesn't differ much form what a car does. The main difference is the ring gear, and ratio. Shaft turns same speed, but "moves" the truck forward less inches per rev than a higher geared car.

[Willie B]

As far as driveshaft speeds.............a truck doesn't differ much form what a car does. The main difference is the ring gear, and ratio. Shaft turns same speed, but "moves" the truck forward less inches per rev than a higher geared car.

Actually, the van I drive every day is an OD machine with a ridiculous top two gears being OD. I remember 6th as something stupid like 1:1.59. When the engine is turning 3000 RPM, the shaft is nearer 4770. This old diesel spins maybe 2500 top speed. I get all the shaking at nearer 1600 RPM.

My thinking is that something exotic in the drivetrain is happening, or one of the joints that has not yet been replaced needs to be.

Of late, my world has been about triage. It's hard to fix vibration when your leg fell off. Yes, an exaggeration, Just a lot happening at the current time on my plate. Too much stuff I have to attend to, a functional truck with a nagging flaw doesn't take center stage, so to speak.

[whtbaron]

That's what I thought too... until it dropped the driveshaft on the ground...