curl is snappy every thing was fine but leaking before the new seals. it will lift the front wheels with the bucket down and hold overnight. the only thing I can think of is on one of the spools had two positions to bolt the control arm maybe it's in the wrong hole. the other 773 machine will lift the rear tires when lifting over limit loads and almost stall. the 763 just sits and hisses seems like no load on the pumpIs the bucket's curl aalso weak under load or not? If this is normal, this is a problem is with a port relief valve. If it is weak, then there are two options - a bad main relief valve or a bad gear pump.
What you describe does not depend on the valve seals. They are designed to prevent oil from flowing out of valve body. . The sound you hear is from the relief valve. Maybe its spring has been weakened, it may not be. If you have weights attached to the machine, that's normal. 763 and 773 are pretty much the same machines, the difference is only in the arms. Due to the vertical path of the arms on 773, there is a slightly larger load capacity. You can not understand without a pressure test whether the relief valve has lost its setting.curl is snappy every thing was fine but leaking before the new seals. it will lift the front wheels with the bucket down and hold overnight. the only thing I can think of is on one of the spools had two positions to bolt the control arm maybe it's in the wrong hole. the other 773 machine will lift the rear tires when lifting over limit loads and almost stall. the 763 just sits and hisses seems like no load on the pump
As to the wrong position of the bolt - check the plunger stroke when you press the pedal, it must be the same as the bucket plungerWhat you describe does not depend on the valve seals. They are designed to prevent oil from flowing out of valve body. . The sound you hear is from the relief valve. Maybe its spring has been weakened, it may not be. If you have weights attached to the machine, that's normal. 763 and 773 are pretty much the same machines, the difference is only in the arms. Due to the vertical path of the arms on 773, there is a slightly larger load capacity. You can not understand without a pressure test whether the relief valve has lost its setting.