I hope I can get some advice on a transmission problem we've had. My wife's 2000 S70 (non-turbo) has been acting up for a while. The transmission will sometimes hesitate and then slam into gear. This happens only when the transmission is warm. A couple of weeks ago, the transmission up arrow started blinking and the check engine light came on. We had the codes pulled by an indie shop and he said something to my wife about a torque converter lock up engagement fault and the check engine light was reporting the TCU fault. We had the ECU software updated by the Volvo dealership and this improved the shifting a lot but there are still some glitches only when the transmission is hot. The car has done 128K miles and I was wondering if a transmission fluid flush would help. The transmission fluid looks original and has some discoloration but it's not filthy. I'm thinking of buying the IPD kit and doing it myself as most places want $160 for the flush. I can't get a supplier for the fluid. NAPA told me it was Dexron IIIG. Where can I get this from? Also has anybody tried using Seafoam Trans Tune transmission additive to the S70/V70 transmission? I've used Trans Tune on the AW70 transmission of my daughter's 240 and it seemed to help. I'm sure Volvo would say it's not recommended but has anybody actually tried it?
Any advice would be appreciated.