as i am NOT a trans expert. i have done 2-3 of those kits. but that was a long time ago. so ill do some guessing. if the instructions did not give you a very specif demintion ill say the the notch was to vent some oil for some reason. to unload some spool or servo. if you can get a diagram of the valve body and match the notch that will show you more info. did that kit make the cooler oil go throu the oil cooler in "P"? that is the real trick. one kit i did gave the 1-2 to shift TO hard. and after 80,00 miles the 7 1/4 spider gears go out. here is an EXTERNAL filter i found. its a cut and paste sorry. the old auto zone 2210 magenfine filter is no longer available at auto zone. BUT i did find the same thing as JX-160 brand-- ATP. at a real parts house uses 3/8" tube. a JX-150 for 5/16 tube. And NAPA 18721. ONLY use high pressure hose. If you must. SAE J1019 217 psi working. NOT fuel hose for a carb engine.