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davidbrady · (This post was last modified: 09-02-2015 22:48 by davidbrady.)

Hi Jeff,

You can definitely rebuild the PTO. My local hydraulics tech very much supports this. I'm not so sure about the pump. You may want to get together with your local hydraulic shop to find out. I know when QCC builds their pumps they bed in on the first run. The gears actually slice into the body to get the fit QCC is looking for. If you put in a new pump shaft, which also has a gear milled into it, you may not achieve the needed tolerances. PTO yes, pump not so sure.

Here's a study I did a long time ago on the SAE B to SAE BB upgrade:

I've attached two outputs from a spreadsheet given to me by a gear professional. One is for the 7/8" shaft, (SAE B), the other for the 1" shaft, (SAE BB).

If you look at the "shear stress in teeth" and "compressive stress in teeth" for the 'Fixed Spline' you'll see:

1) 'compressive stress in teeth' margin-of-safety of -0.129 for the 7/8" shaft and 0.349 for the 1" shaft, and
2) 'shear stress in teeth' margin-of-safety of -0.032 for the 7/8" shaft and 0.487 for the 1" shaft.

My gear guy would like to see safety margins no less than 1.5x to 2.0x.

The 7/8" shaft just isn't adequate. The 1" shaft is markedly better. I'd like to see even better but we can only accommodate an SAE BB upgrade.