As I mentioned in my earlier post, the hydraulic pump is 2 stage, one section should dump to tank at about 1800 PSI, if it doesn't you are trying to pump over 100 GPM at high pressure instead of 48 GPM which will load the engine a lot more and all that extra flow will cause things to slam and pop the reliefs. There are two styles, the early version had the control valve on top of the pump and would dump the front section at 1800 PSI, the later style had the control valve built into the center section and would dump the rear section of the pump, in either case there is a test port and a relief adjustment and another test port to monitor the section that is supposed to dump to see when or if it is dumping, machine has to be above 1500 RPM and above 1800 PSI to check the dumping point or if it is dumping at all. to do the test, bottom out the bucket rollback at low or just above then raise the RPM, the pressure on the dump should drop off at about 1500 RPM, if it doesn't drop off there is an internal problem. You can open it up and look for something obvious, (There have been stuck spools in these pumps.) or take the pump to a Tyrone hydraulic shop or any good shop.