EDIT, ok so I think it could be the brakes dragging, couldn't get it to do it if I hadn't touched the brakes. Then it also did the same thing pulling in forward. Thinking my vacuum booster is going and the brakes are releasing only when the booster looses vacuum.



OK so '87 F-350 460 C6 4WD

When I back in at home it's on a slight up hill grade, all is good, back in, put it in park, etc. Then I shut off the engine and the truck rolls forward downhill like something released. It's like the reverse is dragging holding the truck back until the engine stops and thus the pump stops. Does this happen, if so how, what do I do about it, and is it also dragging while driving forward?

I know quite a bit about my truck/vehicles but auto trannies are the last black art I'm not proficient in. That said assuming the C6 uses a reverse band it seams only logical to assume this band is dragging. And sence it releases when the pump stops that the issue isn't with the band but with the valve body not shutting off pressure to the piston for the band completely.

Is there a way to measure the pressure to the reverse piston? Is flow to the reverse piston only managed by the selecter?

Also posted in the 2 model year based sections that fit my truck: https://www.ford-trucks.com/forums/1...l#post12161816 and https://www.ford-trucks.com/forums/1...l#post12161835