Hi Everyone,

I recently purchased a very clean, good running 1973 142E with an automatic. Along with the car, came all the necessary parts to swap it over to a m40, including a questionable transmission.

My question is, what kind of bench inspections can I do determine the condition of a m40 transmission? I don't want to go through the trouble of removing my fully functional bw35 automatic; just to replace it with a loud, leaky, difficult to shift m40. I'd consider rebuilding the transmission that was included with the car, but I also bet I could find several decent used m40 (if not a m41) locally.

I don't want to keep the bw35 in forever and I have done a swap like this before.

Thank you all in advance.

Colin

I, for one, would not disassemble it. I would first run it through the gears, feel how it shifts. How the shafts turn by hand in all gears.

Then take the cover off, look closely at all the gears for wear, broken teeth. Rust. Run through the gears again and look, and listen, as you turn the shaft.

Drain the oil, look closely for any sign of glitter, rinse and inspect the inside of the case.

If all looks, sounds, and feels ok.. I'd go with it.

Agreed, you can't inspect the bearings. But, chances are they are fine. If it turns out to be noisy, it's real quick to pull it and fix it afterwards. Transmission installation is a tiny part of the conversion process, and removal if necessary only takes about an hour.

M40s behind B20 engines generally last a lot longer than the rest of the car.

--
-Matt I ♥ my ♂

In my opinion, there really isn't much to see with a "bench inspection", and that activity is pretty much worthless - not completely worthless, but not something that I'd consider a complete analysis.

The critical components that you should be concerned with are inaccessible without taking the gearbox apart. Generally, anything that turns.

I do not "take on faith" that any used gearbox is good. For the cost of a gasket set, I think it's worth it to disassemble and inspect properly.

I have no problem with dissembling this gearbox to perform a proper inspection. I'll be looking for damaged or worn gears, synchro cones and other synchro components, and anything else worn, damaged, or cracked. Right?

Any tips, suggestions, instructions, or ideas for doing this? Links to other write-ups or sites are fine.

Thanks again,
Colin

I used Phil Singler's excellent write up in vclassics.com.
He really did a good job laying it out for the novice.