3.73 Gearing

I have a 302 with a 4R70W - (AOD-EW) thinking of 3.73 or maybe 4.10
right now it has 3.31, I cant remember my tire size its a truck with bigger (taller) tires on the rear anyone have any imput on this??

thanks in advance,
Dom

331 to 373 isnt really going to change a whole lot in the rpm department.

what about 4.10 4.11??

Originally Posted by DominickSch

what about 4.10 4.11??

DominickSch,
If you are racing the truck then 4.10 - 4.56 is a good starting point but if this is a daily driver then I have to ask what you are looking for? Are you after gas mileage?; better accelleration?; more highway speed?

the 4.10 rear gears gives you a final gearing of 2.87 in O/D if you want the best mileage then a final of 2.50 is a good target and that would require a rear gear of 3.57. That is so close to what you have that I have to ask - what are you after?

Well if posibale Id like better acceleration and and maybe a little faster
than 110 which is what iv had to up to so far.
As far as gas mileage it may sound funny but I dont care about that.
I wish I understood this rear end gearing better in relation to the trans gearing

Running high numbers on the rear end gearing will decrease your top end speed and give faster acceleration to get there. With less gearing in the rear end you will have a higher top speed but less acceleration to get there. This is assuming that you are able to get to the peak rpm for the cam/engine combination. You may need to put a tach on the engine so that you know what the rpm are and how close you are to the peak at that 110 mph figure. With the 14 inch tires on my mustang and a rev limit of 6000 I have a top speed of 127 mph at my redline (6000) with 3.5 gears. (no overdrive) You have big tires on your truck so you may need steeper gears to get the same speed and you also have that over-drive that can reduce the power to the rear wheels enough that you may get higher top speeds with a 3.89 to 4.10 than you are getting now. Find a speed / hp calculator on the net and run you numbers through it.
You will need to have this information on hand:
HP of the engine at RPM
tire diameter or radius (1/2 diameter)
final drive ratio - rear end + O/D
Weight of the vehicle
might need the frontal area - the height times the width of your truck body as you look at it from the front. ( the good programs include frontal area while the others just assume an average which will make the results faster than you will actually be able to achieve in a truck.