1973 18 Auto (D-180) with a Sundstrand 90-1137 hydro transmission. I have no brakes. The is no external drum, disc, or any sign that there ever was one. Only thing I see is a small lever on the right side, in front of the spin on filter. Moves fore and aft without effect. I've seen later models with a drum and band style brake, but this one doesn't have this. Is there a wet brake internal on this model? Has anyone opened one of these up before? Are reproduction parts even available?