97 Camry won't run forward when accelerating

I have a 97 Camry 4 cylinder that won't run
forward when accelerating, it started little by little
when the car was cold I checked the transmission
fluid it was low I added fluid but still had the same
problem I accelerated to 5000 rpms and it ran . I
changed the transmission oil and filter there was
no metal on magnet and it does not smell burn. On
reverse it runs perfect but when put on drive it
doesn't it just accelerates if I let go of the brake
with out accelerating  it goes forward, well the
other day I got it to run after 2 hours of running the
car and accelerating at 4000 rpms but as soon as I
passed a speed bump it stop I put the scanner and
it gave me the vss code I change it and erase the
code but still same problem and check engine
light went on again and gave me the same code. It
starts fine and engine is normal no hesitation on
rpms. In reverse it goes fine when ican feel the
gear kick in but  when  put on the D and L1 their is
no reaction on the trani like if Iput it on neutral
does anyone have any Idea what it could be
besides the trani.