just bought a 96 tahoe knowing that it had a "transmission problem"...drove it and noticed that i had no tach/speedo...intermittently it would turn on. later i noticed i was stuck in a high gear (3/o'd). so i manually shifted, but only 2, 3 and o'd worked. shut off the vehicle and speedo/tach started working (and stayed on) and was able to drive with all gears (1, 2, 3, o'd). And under WOT, shifted into 1st fine without slipping. this an electrical problem or mechanical? any suggestions?

*check engine light is on. had not had the chance to get codes scanned...