727 Low / Reverse drum size specifications

[43tutor]

I'm in the process of a complete rebuild on my 727. After complete tear down I found the Low / Reverse drum "scored" on OD of the drum. I have access to a machine shop and was thinking about taking a little cut on the OD of the drum to clean it up. I believe a .005" cut will clean it up but I can't locate any specification on the allowable tolerances the drum size can be. I assume, like a brake drum or rotor, there is a minimum size for the Low / Reverse drum.

A new billet drum is not within the budget. I've ordered a complete rebuild kit from TSR racing, including sprag clutch, and I'm following the guidelines set forth in Carl Munroe's Transmission Handbook. Everything else in the tranny look really good except for the Low / Reverse band and the drum OD.

 

[Hemi Rebel]

You cant find the specification because it is not meant to be machined. Who said you need to buy a fancy billet one. How about a stock replacement matching the one you have minus the wear marks

 

[sleepar]

I would turn it like you plan the size won't matter because the adjustment is in the band... put some cross hatches in it like you're honeing a cylinder

 

[miller]

Agree on simply replacing with a new stock drum. Not that much, either.

I've used drums like that before, though, if the wear isn't too bad. Take some 180 grit, and make a wipe at the line from the original surface to the worn surface. If there's no step, I've rubbed down the wear marks to a clean surface, and used it.