Hello all. My 1989 740t has been undergoing tranny slip as of late. The first 3 gears all shift fine, quickly and at the proper areas in the rev range, but the overdrive gear seems to slip whilst engaging. I can switch OD on and off with the OD switch, dropping into third and passing without instant. However, leaving OD active around 3200rpms, the transmission will slip and RPMS shoot up to 4500, with no extra acceleration. Rpms proceed to drop back down to around 3000rpms and the car will continue to accelerate, until they peak 3200 again and it slips some more. I have checked my fluid and the transmission is pending service soon. Could this mean a bad OD unit? Bad transmission? Bad solenoid? Mis-adjusted shift cable?