This question is for the experts of the GATRA bus fleet: is it true that the 1982 and 1983 Orion I's they ran (8217-8219 from 1982, 8320-8322 from 1983) came with Detroit Diesel 6V92TA engines?
If yes, then the transmission behind them would be the Allison HT740 (8217-8219) or the HT747 (8320-8322).
~Ben