Wow, that is almost unbelievable, but very nice job indeed.
I have a 1986 MF 1030 HST just like that with about 1,400 hrs of seat time on it that I purchased new was back when. Still runs like new.
Never had any problems with the hydro. I suggest that you change out both of the transmission filters, the high pressure and the low pressure. Then fill with a synthetic hydraulic fluid, preferably a multiviscosity one like Amsoil 5W-30 hydraulic fluid, instead of a straight cut hydraulic fluid. The hydro really like the synthetic oil, you will notice a distinct difference in operation.
Also, look closely at your undercarriage and inspect all of the metal high pressure lines underneath and make sure that none of them are crimped or crushed, especially the long line coming back from the hydraulic oil cooler in front of the radiator back to the transmission. If any of the lines are crushed or obstructed, you will not be getting full pressure flow and not have full power through the tranny either. I accidentally crushed that high pressure line on mine (coming back from the oil cooler) and it only produced about 50% of the power that I was accustomed to, until I changed out that line, then it was very powerful indeed.
Also, inspect the rubber connection hoses going into the hydraulic oil cooler too, they could be collapsed and not allowing full flow either and result in excessive heat build up.
Again, that is some kind of nice job, even your custom A/C job is amazing, enjoy! /forums/images/graemlins/wink.gif