THE 4SPEED TRANS HAS GEAR RATIOS , THE RATIO CHANGES WITH HOW MANY TEETH ON EACH GEAR . AND THERE ISN'T VERY MANY COMBO'S . I HAVE RACED BOTH 4 SPEED CARS AND AUTO CARS EVEN A FUNNIE CAR WITH AIR BOX, AND LAST BUT NOT LEAST A 904 AUTO. BEHIND A 20 OVER 360. IN A 72 DART . HERES A GOOD CHALLENGE IF YOU ARE RUNNING A 360 WITH J HEADS POST YOUR 60 FT TIMES AND 660 TIMES AND MPH LETS SEE WHO IS FASTER? IF IT DOESN'T RAIN SAT NIGHT I WILL POST MY TIMES . SO FAR MY BEST 60 FT IS 1.42 AND 6.40 660 GOOD LUCK 4/ SD.