TZ25DA HST wont move after hot

My friends TZ25DA New Holland with Hydrostatic Trans slows and quits moving after about 30 to 45 minutes and eventually will kill the engine if she tries to get it back to the house. If you let it cool down it will work fine for another 30 to 40 minutes. The front end loader and bushog quit working also as if it is losing hydraulic pressure but will lug engine down and stall it if you keep going.
This tractor only has 97 hours on it but is out of warranty. Our New Holland dealer no longer sells New Holland but was able to give me the Wix filters cross overs. I drained the hydraulic tank and changed the main hydraulic filter and the hydrostatic filter and changed engine oil and filter and fuel sediment bowl filter. The hydrostatic filter had gray fluid with tiny metal particles in it. The hydraulic tank fluid and main filter had clear fluid come out when removed. Tractor had all New Holland filters on it before servicing and had this problem. After changing all filters and fluids it still stops moving after 35 to 40 minutes.
Thanks for any help. New Holland should fix this Tractor because it has such low hours but we no longer have a local dealer.
Thank you for any help.
Kenny

Welcome to the forum Kenny. Sorry to hear about your problem. I'm hydraulically challenged so I can't help but hoping someone here can offer some thoughts.

Hi Kenny, welcome to net tractor talk.
That's a new one to me. I would have guess perhaps you were low on fluid or a plugged filter but since you've changed the fluids & filters we know that is not it.

Sounds like something is overheating and shutting down to save the system from further damage. If I understand you correctly the engine still runs but none of the hydraulics work. My guess would by the hydraulic pump ...only a guess though. .....With only 98 hours on it that pump should not be it. I sure will be interested in the solution whenever you do find it.

Double check the fluid levels for the hydraulic fluid. Also confirm the correct type of hydraulic fluid was used.

Does it have a screen in the transmission? If it does, it could be stopped up. We always clean the ones in our JD tractors when we change hydro fluid. Might be worth a chance to change the trans again .What brand of trans fluid was used ??? Bordercollie