1996 F53 Chassis Ford Motorhome, 460 gas, 25,000 miles. Started a few months ago, about 400 miles ago. Shifts extremely hard in all gears, hot or cold. Seems to me I might have seen the OD light flash back then, but it was out of the corner of my eye, and I thought it flashed but was not sure. I cannot find the diagnostic data plug to scan it. I am about ready to start taking the dash apart. Any ideas on location of plug or diagnostics of transmission? BTW speedo works fine, it shifts at the right points, no unusual noises except the dishes rattling.