This is going back over 20 years, but I've rebuilt a few of those winches (company I worked for went bankrupt back in 1986). I used to build and install oilfield decks, live rolls, do frame stretches, install pumps, blowers, PTO's, winches, cranes, etc., ets., etc....
Is there a small plate on top of the gear housing that you show in pic #5? If so, it should give you a model number. Off-hand, it looks to be around a 12 to 20 ton high-mount winch you have there.
It's been a number of years, but PM me any questions you may have and I'll see if I can sweep some of the cobwebs from my rusty brain and try to help you out.
Lane
