Thread: reverse hellllllllllpppppppPPPPPP!!!!

Did you check the shifter linkage to make sure it lines up properly between the trans and the shifter itself? If it is no aligned correctly it can cause low pressure. Also when you rebuilt the trans did you use an OE lip seal on the reverse apply servo or an aftermarket long style lip seal? Reverse is not a very common problem to have and there are only a few things that can cause it not to work properly and the apply servo is the only thing you can get to externally.

Since the linkage is ok and the seal sounds right you arent left with much that could be wrong. If the lip seal rolled out of the groove or wasnt seated all the way when it was installed that can cause your problem also. Other than this you are left with a potentially damaged channel plate gasket, boost valve problem in valve body, or unlikely a band problem which shouldnt allow it to work at all. As far as the trans working on the dyno.... That is a big reason I am not a huge fan of them. They may test OK on a dyno but there is no way to simulate real world in-car condtions except in-car. With minimal load or drag on the output of the trans reverse may have seemed to work fine. Now that you have a 3500lb car working against the holding power it adds more into the equation.