Spooky transmission

i have a 1999 ford escort lx with 250,000miles. two weeks ago i put in a new remanufactured transmission for $1400 from advance auto. my trans no longer slips on the highway, but it (occasionally) still slips up hill in 1st gear. what the heck did i miss? any ideas would be appreciated.

Auto or manual transmission? Could you provide a better description of “slips up hill?”

automatic transmission.
when you stop on a hill then try to accelerate it just slips and the engine revs up but won’t go.
after putting it in park again then pulling down in drive it will take off…

The obvious question: Did you check the fluid level?

yes it’s full, does an escort have a transmission computer or other device that tells it to enguage?
could it possibly be a broken motor mount?

Make sure that you manual linkage is correctly adjusted according to the book. Then, do or have done a pressure check of the line pressure. Do it in forward gears, reverse, and at stall in forward gears. It is possible that the remanufacturer did not renew the pump.

Also on a lot of remanufactured transmissions you use your old valve body. If that is the case, make sure that the old valve body is cleaned and that the main pressure regulator is not sticking and sliding freely. Also did you back flush the transmission cooler in the radiator and replace the torque converter if the old transmission showed a lot a debris in the pan?

Let us know how this progresses.

One more thing about the fluid level… Did you check the fluid level with the transmission HOT, and with the vehicle on a LEVEL SURFACE???

transman