Contour Enthusiasts Group Archives Forums Modifications Transaxle Too much MTL?? How much fluid is needed

There isn't really anything that will be damaged unless it was really overfull. Some transmisions only take around 2.5 quarts, on the slope 3 is reasonable. With only a half quart over in there there will be no damage. It may do nothing negative at all.
Normally, if you overfill the transmission you suspend all the gears in the oil and dramatically increase drag from fluid friction. This robs you of horsepower and fuel economy (in a simplistic sense). Only the lower gears usually touch the oil. THe spinning action carries the fluid up to all the gears because it is thick and sticky and it is this property that is designed to lubricate all the rest of the gears while minimizing friction.

If it completely full then when it gets hot the fluid will expand and blow out your seals and begin to leak badly. That is the only real damage I can think of in this transmission.

Bottom line, with 3 quarts I'd not sweat it unless the thought that you might be sucking up some extra HP bothers you.