You sure it works well in forward gears?
Filter and oil change will NOT fix transmission problems. The transmission is a closed loop system. The only thing to plug up a filter is transmission parts (Seals and clutch packs). If the filter is plugged, you got bigger problems.
It may be as simple as a loose wire or broken solenoid? However based on your description of the problem, it could be a clutch pack that is toast and a rebuild is needed. Some power in reverse typically means everything is working, however there isn't enough force for the clutch pack to engage properly. Could be the fault of a solenoid, or worn out clutch pack. Not sure on that particular tranny, however most reverse clutch packs are the same as the 2/4 forward clutch pack on 4 speed transmissions. Reverse is engaged by a sun gear. If the 2/4 clutch pack is the problem you will have a hard shift from first to third, skipping second completely. Did you hear a load snap before it stopped working in reverse?
Did you say the tranny fluid has an odor? like a burnt smell? if so, she is toast. If not, a rebuild may not be needed, unless the sun gear is toast.
HOI Crappie Club
Where family and friends come to compete for a little more than bragging rights.
Quick, someone teach me how to fish so I can win this tournament!!!