Did a rebuild on my 670 transmission. It seems to be working alright, drove it over 80 miles, however it shifts into third at 50 m.p.h. and downshifts into second at about 45 mph. There is also a slight shudder in reverse, but that seems to be getting better. Cleaned everything spotless and used mopar ATF+4 synthetic transmission fluid. Also used a Superior shift kit. Upped the pressure as per the directions and made the other changes. Any ideas of what I can do to make it shift at the correct speed?