Transmission ID help?

In my 1966 American I have identified the engine as a 1968 199ci. The transmission is a 3 speed automatic, aluminum case, so i figure it is a Borg Warner. Numbers on the transmission are; 2622 located on a tag(it appears to be riveted on) just forward of the shifter, and ATBS stamped on the case, on the shifter side, just before the tail shaft. What year and manufacturer?

68 used an M-36 from the factory. The 36 may or may not have provisions for a trans fluid cooler, it may be air cooled in that application regardless. If it's air cooled there will be a big opening on the passenger side of the bell housing. Make sure the cover on the lower front of the bell is on or the air cooled model will over heat. The M-37 was used behind the 232 that year and it DOES have fluid cooling provisions, some may be air cooled.

If it has a TV cable (a "kick-down" cable) it's a 62-66 model, as rev said. The later models use an electric switch on the throttle linkage (usually mounted on the intake) to control an electric solenoid inside the trans for kick-down. 

The cable we were talking about is for the kick-down only, not shifting, but you have a vacuum modulator, so no cable.

The tag should have a number on the lower left corner. Unfortunately the numbers were screen printed on the tag -- the stamped number near the center is the serial number. If the tag has been painted over you can use mineral spirits or paint thinner to try and wipe it off, but be careful you don't wipe the black screen printing off too. The black screen print ink is harder to wipe off than paint.

The casting numbers and such don't help a bit. It could be a 66 or 68 trans, both years used the M-36 behind the 199. That said it could be an M-36, 37, or 40. Basically the larger number is a little stronger than the smaller, but not much. There are other differences. The M-35 is the original aluminum model and it had the TV cable (like a GM 700R4) and was only air cooled. The 36 has the vac modulator instead of cable (all but the 35 does). It may or may not have provisions inside for a trans fluid cooler. The 37 definitely has cooler connections, I'm not sure if it was ever used in air cooled mode or not. The M-40 (and later M-4x versions) were never air cooled, not in AMC cars anyway, all liquid cooled. All that is needed for air cooling is the special bell housing and torque converter.

Air cooling works surprisingly well! TomJ drove his 64 Classic wagon with 232 and air cooled M-35 (may have been 36, but I think his car was originally a 196 that he changed over to a 232... might be wrong though!) across Death Valley and into the CA mountains a lot and never had trans problems. He often had a load for camping too!

that little aluminum auto trans is a fine thing. air cooling is plenty adequate (i assume you are not racing :-) keeping it adjusted is CRITICAL though but easy. i had one for 23 years (same trans) in a 63 classic behind a 232, towed trailers, 350,000 miles (two or three full rebuilds) and it never overheated, and i added a gauge to it (siliconed it to the case up front and kept air off it).

it's a nice sweet spot of engineering and product. it's not even that inefficient. i think it's limitation is power capability, but within that it is as good as anything.