Had the car sitting for a few weeks. Been running fine for thousands of miles. Fired it up, and drove as it should. Afterwards, i let it sit for a few hours, and now the trans just revs in 3rd and 4th! It's as if you drive down the road, accelerate, then all of a sudden the motor is just revving!

Shifts fine from 1st to 2nd. N, R, and P are fine too.

Vac system looks fine and hasn't had any problems.
Fluid level looks adequate.
Unplugged the kickdown switch with no success.
Bowden cable is intact. Might be improperly adjusted, but intact
Changed trans fluid/filter about 20-25k mi ago. Fluid looks clean and doesn't smell burnt.


Any ideas?? Thoughts??

I have not messed with that green modulator valve on the trans. I have not used TranX yet.

Perhaps the green vac modulator died? Varnish or crap settled in the valve body??