STD C6 converter acting like a high stall?
I need some advice on a standard stall converter in my c6 auto that seems to be acting like a 3000 high stall. The gearbox has been fully rebuilt except for the torque converter and works well except for stalling up to about 3200 rpm and seem to be worse when cold. After start up when cold it revs to about 2500 just reverseing out the driveway which is abit uphill. Could it be that the converter is stuffed or maybe other problem? Car info is 75 F100 4x4 with 393 clevo, 2v well ported heads, edelbrock torqer manifold, 214-224@50 cam, rollers ect. Gearbox has extra clutches,R code billet servo,shift kit, 4.11 gears 39 inch tyres. I dont really mind the stall speed as it launches well but I do a lot of 4x4 driving and tow a big trailer and this slipping becomes annoying. Any ideas would be a help.