I just drove my '02 7.3L Excursion home after having a new triple disk torque converter and Sonnax pressure regulator valve installed in the 4R100 tranny and when I was parking it at home I noticed that the transmission now slips and shudders in reverse. It was perfect before the install. No problems at all in forward. Fluid level is good. I shifted from forward to reverse like 20 times hoping that maybe some fluid circuits just needed to be filled, but it didn't help. I'm going to bring it back to the shop tomorrow, but anyone have any ideas of what might be going on here?
Reverse requires a lot more line pressure to operate than the forward gears, if the pressure regulator valve train was improperly installed or has a problem it may not be able to produce the line pressure needed for reverse to work properly. The use of a pressure gauge will tell if the line pressure is sufficient or not.
Reverse line pressure at idle - 75-99 / stall - 240-265
Drive line pressure at idle - 55-65 / stall - 156 - 174