Have 92 F150 with E4OD, 138,000 miles. Used for occasional towing. Has been "bang" shifting intermitently into all gears for many years, but getting worse. have changed all oil & filter until pan bolts wore out. have tested and changed all parts including solenoid pack. had it electronically diagnosed, no faults found. Can it be the accululator valve body or is there a main pressure relief valve in pump? line pressure spikes high at times of problem. Please help. Driving me Crazy.