Archived automatic problem - truck down

[78repowerwagon]

Condition is no go in reverse or forward, acts like neutral, but slightly surges forward when throttle is applied in low. Here are my pressure readings:

Manual low: Accumulator port 88psi rear servo 90psi @1000rpm

second:accum 88psi @1000

drive:accum:88psi@1600 front servo:90psi

reverse:rear servo 260psi @1600

overdrive: accum 110psi and od 106psi @1600



The transmission is strong in 2nd drive drive and overdrive, at least on jackstands. I can pull the engine down with the brakes in drive on stands. To get it to shift in second, it must be on stands and run through first.



I pulled the valve body to do an air test and found everything strong. According to the chart, in reverse, the front clutch rear band and direct clutch are applied. Ruleing out the front and direct clutch because they are strong in 3rd, it leaves the band. In low the overrunning clutch should be holding first, plus it is holding in second. I overlooking something, but what? Could a valve be stuck?

 

[wtrenholm]

Being that you have good pressure numbers, you shouldn't have any leakage internally, (ie- lip seal, seal ring, servo piston, etc); also the trans & t-conv can transmit power in 2-3-4, so major mechanical breakage is also out.



The only common component to 1st and Rev is the rear planetary is used to transmit power in those two gears, in all other gears the rear gearset is just freewheeling. If the problem suddenly occurred out of the blue, my guess would be a mechanical breakage of the rear gearset in some manner.



HTH,

Wayne

 

[78repowerwagon]

Looks like I will be pulling it tomarrow. I know I was missing something, but was hoping it was something which would require less labor.

 

[Reb.B]

converter is shot.