The IH 444 is only 38 PTO HP. They also had a real fast high gear. So it pulling down going up a hill is NORMAL!!! Don't turn the fuel screw up. The IH 444 transmission was not that heavy to start with. Couple of friends have them. They have had transmission issues.
The IH 444 is IH version of the MF 35 or 135. These tractors with a loader going down the road are going to PULL!!!