We have a Trek T900 that is a lot older than yours. It's a good bike. We also have a DaVinci Grand Junction. When I have purchased new grip shifters, the cable they come with is not long enough for a tandem. I just bought shifter cables: Jagwire Slick Stainless Derailleur Wire 3100mm Shimano, $6.49 each from Ben's Cycle online (free shipping). I find no LBS in New Orleans keeps shifter cable that long in stock. I find it wise to order 1 or 2 extra in case for some reason you run into trouble and have to pull one back out and it frays on you. Bummer about your previous owner who let it rust.
Last edited by jethro00; 11-03-20 at 10:36 AM.