Learn me: bench testing a transmission

I'm working on putting a 66 MGB back together. The original 3 synchro transmission is perfectly usable, but I have 4 of 5 of the later 4 synchro variety laying around. Once I finish rebuilding the engine, is there a good way to test the transmissions before I waste time putting one in the car? Obviously a visual inspect of the internals is in order, but is there a way to be a little more sure it's going to function correctly?

Thanks, Bryan

Not really. Put it in each gear , turn the input shaft, see if is smooth and turns the tail shaft. Don't forget reverse.

Yeah, that's what I figured. Been through that already, just thought I'd see if someone had a clever way of being more sure. Thanks much.

The way I bench test them is to find the one that looks the best and install it. When it doesn't work I pull it and install the 2nd one. When it doesn't work . . .

The last one is always the one that works.

for an auto you could test with air to see fi the clutches are engaging (must have plate usually though, and not sure if this testing is universal) but for a manual all I can figure you could do would be make certain it will go into each gear and spin

With LBC's, sometimes the input shaft is small enough to chuck into a 1/2" drill. That's what did before installing a j-type in a Spitfire. IIRC, it worked on a Volvo M41 as well.

Granted, it's not a definitive test since it's not under load, but it does work well enough to listen for things being assembled correctly. Obviously, you have to stop between each gear.

Why do you have to stop? There is virtually zero torque loading, probably equivalent to the mass of a spinning clutch plate (when clutch pedal is depressed). It seems like a good way to evaluate the synchromesh action, ie, put it in first, spin the input shaft up to speed with the drill, shift to second, then to third, etc. Listen for the Graunch! sound. If the synchromesh cannot handle that minimal loading, then it has no chance in the real world.

Carter

Well, to be honest it's been a few years, but I seem to remember that didn't really work - I did try. However, the trans has been fine in the car since.