we use the formula that was at that web site and

28inch tall Tire size + a 4.56 gear = 7,200rpm at the 1/4 mille ? 118.00mph ?

that can't be ? any body running a 4.56 gear ?

I get 131.5 mph. Go HERE (http://www.chevelles.com/shop/programs.shtml) and download Speed.EXE. It's very handy for caluclating converter slip, rpm drop between shift and several other things. Makes calculating these things very easy.

BTW, what is considered acceptable converter slip?

I'm at 116.3 to 117.1 mph at the stripe, between 6700 and 6900 rpm. Too much shaking (rough track) and a down hill shut down to watch it close. 4.56 gears 28 X 9 ET drags. If 28 X 4.56 is supposed to get 131 then I guess I have a fairly large amount of slip occuring. Gary

my truck goes 7100 rpm with 4.56s at 120.3 with 28x13.5 et streets...thats with a 4800 stall

I cross the stripe at 6800, 4.33s on 26" slicks,( no converter) so it doesnt look like much converter slip going to a larger gear and the next tire size. Oh MPH is 117-118.5.

Originally posted by accontrol:
we use the formula that was at that web site and

28inch tall Tire size + a 4.56 gear = 7,200rpm at the 1/4 mille ? 118.00mph ?

that can't be ? any body running a 4.56 gear ? 7200 rpm, 28" tire, 1.1 high gear ( this is with the 10% slip ) 4.56 gears = 119.568 mph. You may experience some tire growth so your speed may be a little higher.

http://www.angelfire.com/fl/procrastination/rear.html

I go through at about 6700 at 114.xx. 4.56, 28" tire. This is with about 8% slippage.