Swapped in a C6 about a month ago to replace a worn out manual OD trans on my '85 F150. I noticed I have to really give it throttle to take off from a stop, then it has a harsh 1-2 shift. If I take it easy I get a nice smooth shift.

My thought process is that since I'm having to use a lot of throttle to get going, the trans "sees" low vacuum and wants to hold first gear longer.

Possible wrong torque converter with too high of a stall speed? It's a low mile Jasper reman trans that came with a torque converter. It just seems like the converter feels loose. I can power brake the truck and the engine rpm goes up to 2000-2200 before the wheels want to turn.

Its not helping my fuel economy either...lol. I'm thinking it's some generic converter that is set up more for v8 use.

Any thoughts?