Front Drive Shaft grrrrrrrrr findings so far. .

[green_machine]

I went with out-of-phase.

No vibes.

I have Grrr... when letting off the gas going around 60.

If I override the overdrive the Grrr. goes away completely.

that's because you are changing the rpm of the shaft, which changes the harmonics of the load on the output bearing...

 

[Tools R Us]

that's because you are changing the rpm of the shaft, which changes the harmonics of the load on the output bearing...

Overdrive has nothing to do with the RPM of the driveshaft.

 

[green_machine]

Overdrive has nothing to do with the RPM of the driveshaft.

yes, it does....

if you change the drive ratio, you will the shaft rpm. "overdrive" is nothing more than a gear ratio, which does change the output.

 

[concretejungle]

Are you sure? I was thinking that the RPMs would increase due to gearing in the tranny, yet the revolutions of the driveshaft would remain constant. Otherwise when you shifted the OD off or on you would get a big jump or decline in speed.

 

[-Spike-]

yes, it does....

if you change the drive ratio, you will the shaft rpm. "overdrive" is nothing more than a gear ratio, which does change the output.

It doesn't matter what gear you are in, if the truck is doing 50 MPH the driveline is moving at the same speed, first gear or OD. MPH is measured by how fast the driveline is spinning, not the engine RPM.

If you change the gear ratio in the differential, that would effect the driveline speed vs. MPH. Changing the gear ratio before the output of the T-case has no effect on MPH.

-Spike

 

[landtank]

provided all four tires have traction the driveshaft's rpm is constant at any given speed. The only thing that will change this is changing the diff gears because they are the only thing down stream of the drive shafts.

 

[green_machine]

ok, let me clarify

the ratio of the output changes the engine rpm, therefore changing the load / harmonics / angle of the driveline. does that make it clear?