Note that DEX III is no longer licensed by GM. Only DEX VI is.

One could put oil removed from a WWII jeep, put it in a container and sell it legally as DEX III. DEX III should never be bought or purchased as it no longer has any specification requirements whatsoever; GM no longer approves the use of DEX III.

DEX VI can be expensive. Wal-mart sells it for about half what Advance Auto and Autozone sell it for. Wal-mart has a problem keeping it in stock, so be prepared to visit a few Wal-marts to get the qty you may need.

well i changed the trans filter cleaned everything up good replaced fluids put in some lube guard,and still no reverse. the car shifts great in forwards gears smooth ,better then ever , but reverse is still not working , ill try to explain this better cause i think its still fixable. maybe im wrong ,but when i put it in reverse the trans bumps like its going in, but when i hit the gas its like its trying to go ,it acts like e-brake is on ,also engine sounds like its skipping only when i put in reverse and step on gas. so im think vacuum line is there a vacuum line to solenoid or servo on 4T60E ? i have also dropped the pan again ,but before i did i put some trans flush in it thinking that maybe cause i didnt clean up inside valve bodie that theres still something plugged up.so when i dropped the trans pan again the fluid wasnt red like when new was dark like almost turning black again ,and there was more sludge in bottom of pan again , i only drove the car around maybe and hour or so trying to see if reverse would work again. im gonna try here again to see if anyone has any ideas what this problem might be ,prolly put it back together and take to trans shop have them put tech-2 on it see whats going on , TYall for your time ,David

Sounds like your reverse reaction drum. Funny thing is, in 1997 it was supposed to be upgraded. THM 4T60-E - New Reverse Reaction Drum For 1997 Models - OBD2 Car Diagnostic Tool Shopping Guidance - Launch X431 Master Tech