Decided to check the charge pressure on my 753. Book says 200. Gauge says 110 at idle and 170 full throttle. Oil level is correct. Not sure of location of relief valve. Going to pull hydrostatic drive out and tear it apart. Other issues besides the low pressure. Anything special I should look for. Bottom red light on dash lights up at full throttle also. Think its the trans light. Symbols long gone. Thanks