Son's 2001 Avant, needs a new auto trans, books say there was only one tiptronic transmission used with the 1.8T in 2000 and 2001 coded as model FAL.

Question is, will any of the other versions of automatic transmissions from say 98 thru 2000 1.8 or 2.8, 3.0 engines bolt up and work without setting off all kinds of error codes? The only differences in parts on the FAL from others all seem to be small internal internal pieces here and there. Some of the transmissions have different side axle output flange sizes and those would obviously be a problem, but it the outputs flanges were the same size, and the final drive ratios were the same what else will work? The FALs are hard to come by without paying more than the whole car is worth.