I just finished reading this entire thread (still digesting!) and it has give me a little hope!
I just bought a 2000 montana since the Grand-AM was no longuer big enough due to the latest addition to our family (it's a BOY!). I tried the van long enough to warm it up good before buying it and there was never any issues what's so ever. So we bought it... Only after driving it home (was 4hrs away) did it start the hard shifting thing! I stopped at my brother in-law who is a mechanic and plugged in his scanner. There was a few codes:
P0742 (TCC stuck ON) or something like that
P1811 (we all know what this one is)
and other codes for the O2 sensors... All fluid levels were fine so we erased the codes and drove the rest of the way with absolutely no issues at all?!... Like everyone else it works fine untill it's warmed up then comes the hard shifting. The engine light came on again and the only code that came back was P0742 (no P1811 this time) & the O2 sensor thing again...
I bought some Seafoam Trans Tune and dumped 1/2 the bottle in it (20 kms ago) and the hard shifting is still present except now it doesn't get REAL bad where the van jerks, it just shifts harder then normal & havn't got another code yet.
I want to do a fluid & filter change (already bought the filter & 8ltrs of DEXRON VI) but now I want to try this shift kit that seems to do miracles and save everybody big bucks!!! The only thing I'm not sure is the type of transmission is in this van. Are all 2000 montana equiped with a 4T65E? Would I order the kit which the link in the above post brings me to? I seem to be the only one with the P0742 code, would the kit help resolve my problem?
Thanks ahead of time for any help you can bring me. And a special THUMBS UP to bnaylor for all the help you brought to all these satisfied member! Keep up the good work!