9" Ford question....

[Sean]

Are all 9" centers the same? I have a 3.90 geared Locker in my F100, but I bought a clutch-type posi unit at a swap last year and have been thinking about rebuilding it and putting higher gears on it.  That way I can put lower gears on the Locker and have something ready for the occasional trip to the Strip.

The original Pumpkin had 3.08 gears and was an open diff. I tore the spiders up about two days after I put the original SBC in the truck, but the Ring and Pinion look good. Can I just swap the Ring gear onto the Clutch-posi unit and drop it in place of the Open unit? Or are there differences that I need to be looking for?

All the parts in question are 28 spline, but I don't know if different carriers are required at some point in the gear ration span.

[Darkman]

You should be able to swap the gears. You might have to use the front pinion bearing support and yoke.

[Sean]

You should be able to swap the gears. You might have to use the front pinion bearing support and yoke.

I wasn't going to remove the pinion. I figured if the differential units were the same, I could just put the ring gear from the open diff on the posi unit and drop it right back into the pumpkin.

Or not?

[enjenjo]

You should be able to swap the gears. You might have to use the front pinion bearing support and yoke.

I wasn't going to remove the pinion. I figured if the differential units were the same, I could just put the ring gear from the open diff on the posi unit and drop it right back into the pumpkin.

Or not?

You can. Just make sure to check the backlash before tearing it apart, and set it back to the same measurement when reassembling. Otherwise the wear pattern will be different, and the gears will wear fast.

The only thing that may be a problem on the housing that was originally a 3.00 gear, the pinion support is notched on 3.50 gears and higher, but not on the lower, numerically, gearsets. So you may have to notch the pinion  bearing support to clear the ring gear. No big deal, you can do it with a 4" grinder.

[Sean]

That should help my mileage out a little. Right now 60 mph is just over 3000rpm.

[mopar2dr]

We used to swap out the centers on our race car depending on what track we were running. You would be surprised haw fast a coupe guys can do this with a lot of practice. As long as your sticking with the 28 spline axles it should be a snap. We also would put a couple small beads of weld on the axles to keep the bearings from slipping allowing the axle to work out. Nothing worse than seeing a tire,wheel and axle flying through the air.