95 4l60e has weak reverse but good in all forward gears ??????

[rickpilgrim]

Our 95 k2500LD has a reverse problem.
This is an obd 1 truck, no plug in and read codes. It is a fully electronic 4l60e and has no tv cable but the provisions are present(throttle bracket and trans case has a tapped bolt hole but it is not drilled for cable. There are 1500 miles since rebuilt by po.
It also had a new pump assembly and converter as PO installed rebuilt transmission improperly and damaged both- then sold us the truck. Fluid looks just like the day we refilled the trans- looks new.
In all forward gears there is no slippage, just nice solid shifts. You can feel in engage in all gears, even reverse.
But- at IDLE on flat land it backs up, but apply any throttle and it's like neutral.
If you have to backup it will also engage at full throttle.
Ideas?

 

[NickTransmissions]

Our 95 k2500LD has a reverse problem.
This is an obd 1 truck, no plug in and read codes. It is a fully electronic 4l60e and has no tv cable but the provisions are present(throttle bracket and trans case has a tapped bolt hole but it is not drilled for cable. There are 1500 miles since rebuilt by po.
It also had a new pump assembly and converter as PO installed rebuilt transmission improperly and damaged both- then sold us the truck. Fluid looks just like the day we refilled the trans- looks new.
In all forward gears there is no slippage, just nice solid shifts. You can feel in engage in all gears, even reverse.
But- at IDLE on flat land it backs up, but apply any throttle and it's like neutral.
If you have to backup it will also engage at full throttle.
Ideas?

My guess: inner-most seal on the low reverse piston was lacerated upon installation into the back of the case (was not installed square and/or insufficient assy lube used).

Its also possible the reverse input drum lip seal was lacerated but not as likely. Trans will need to come back out if im correct.