haulinoats

My 1999 4wd Tahoe (124,000 miles) has been shifting hard going into 2nd and 3rd gear. Not a big additive fan, but using Lucas Transmission fix has at least kept the problem at bay until we can figure out whats going on with it. Have been putting it in the tranny about every 3,000 miles- skipped putting it in with last oil change and it made a huge difference. This time the check engine light came on (it dosen't unless it really gets bad, this was the 2nd time ever it came on), diagnosed as a "generic" transmission code- meaing some problem..some where. The problem has been very intermitiant- such as if I drive it to work and its shifting hard, chances are it wont do it on the way home or even over the next couple days, but the problem always picks up again with verying degrees of sevarity.

Ive been scouring this message board in the hopes that you guys could help me- I did find a couple of guys with the same issue, back in 96 and they figgured out that it might be the valve body in the Transmission. (They also noticed that it happened when their gas tank got to be 1/4 or so full... i've seen no correlation)

Anybody else with similar problems or have any ideas? It's sad how much I'm in love with this truck...