What actually happens during a transmission rebuild?

Summary:

Jaden separates a rebuild into soft parts and hard parts. Every rebuild gets all new soft parts, which he lists as clutches, bands, bushings, washers, bearings, seals, gaskets, and pistons. The shop also addresses known failure points, so if a particular transmission has a solenoid that commonly fails, it gets replaced while the unit is apart. Hard parts, such as the case, pump assembly, and drums, are handled differently. Those go through the shop's parts wash, then get inspected and measured, and they are only reinstalled if they measure within specification. Anything out of spec gets replaced. He also states that an automatic rebuild always includes a new torque converter. Asked about manuals, he explains that a manual rebuild covers bearings, gaskets, seals, and synchros, since gears and shafts usually survive, and that manual transmissions have no torque converter at all.

Answer:

So when we rebuild a transmission, we put in all brand new what we call soft parts. So the soft parts is clutches, bands, bushings, washers, bearings, seals, gaskets, pistons, all that kind of stuff. That's your typical rebuild. And then we also do the common failure points. So if there's a common solenoid that fails in this transmission all the time, then we're going to replace that while we're there. What it doesn't cover is the hard parts. So when you get into the hard parts of the transmission, that's like the case or the pump assembly or the drums. All those go through our wash and then we inspect them and we mic them, and if they're within spec then they get put back in, and if they're not within spec then they get replaced. And then you always get a new torque converter. Always a new torque converter. Manuals is different. A rebuild on a manual is typically going to be bearings, gaskets, seals, and synchros. Most stick shift transmissions are going to have all the gears and shafts, and most of the time the gears and the shafts are okay. It's the synchros and the bearings that wear out, so that's what gets replaced in a rebuild. But again, we put it all through our wash, and if third gear is bad, then we replace the third gear while we're there. And there is no torque converter in a manual transmission.