. Check engine would come on at times and stay on a day or so and go off. Might be 6 days or 6 weeks before it would come on again. Son was using vehicle and both check engine and wrench lights came on. Upon driving it home (10 miles) once up to highway speeds the engine would build RPM's and engine would "downshift' ? As if you were going up a slight hill. Letting off throttle is would drop off and RPM's would go back down. At slower city street speed all I notice is it takes a bit to shift into 2nd gear. No slipping . Goes into reverse easily. This transmission was rebuilt 3 years ago. Only been driven 7 to 9 thousand miles.