Ok so I found out my 86 f150 has a 3.55 rear end, I have 31x10.5's on it and was wondering what does the over all gearing come out to be with that rear end and tire combo


Thanks

 

i dont know if this helps but you can go on richmond gear website and they have a caculator that you type in weight, tire size and rpm and it tells you the gears

 

no tach

 

You already know your actual gear ratio, so that's your actual gear ratio. The calculator will only tell you what that is... I think what you are asking is what is the 'effective' gear ratio with the taller tires and that would be a comparison to what the stock truck tire size...

Assuming your truck came with 29" tall tires from the factory, now that you have 31" tall tires, it's like you have a 3.32 gear ratio when compared to stock....

So, to get your trucks 'effective' gear ratio back to stock with the 31" tall tires, you would have to go to a 3.79 gear ratio, but since they don't make that, you would have to settle for 3.73's... But, you won't really 'feel' all that much difference IMO... For the same money, go to 4.10's and you'll feel it for sure. You'll see about 300 more rpms with the 4.10's compared to your 3.55's going 60 mph in 3rd gear (1:1). 3.73's would only be about a 100 rpm difference...

Mitch