Hi
I have a very important question. I have a 97 F250 H/D witha a 460 gas motor. The truck came with 3.55 greas. It also came with (after a metric to domestic calc) about 30" tires. After a long story and changing the tires 3 times I ended up with 35" tires. I pull a 33' trailer and don't seam to have as much low end tourqe. After some reserch I came up with having to change the dif grears to about 4.10 gears just to get back to factory low end tourqe.
Like I said I did some research to get here. Now I speak to a freind in a tranny shop and he started laughing and said I ws crazy. He said I should go with a custome converter. Now I am the one confused. I felt it was simple math and that if you change the tire diamiter you new to change the gear ratio to make the correction. Anythoughs?

 

You are correct. If your running 35" tires you need to change your gearing to 4.56's. If you do a lot of towing you might even consider 4.88's since the 35's are a lot heavier than the stock tires and you would notice a big improvement on take-off. Hope this helps.

 

Run from the laughing torque converter guy! Changing your tires would be alot cheaper on a 4X4. Changing the gears would be the normal procedure if you're fixed on a certain tire height. You should plug a few figures into a gear calculator to find a desirable choice.

http://www.ring-pinion.com/content/calculators/RPM.asp

 

Thanks very much for your help. It makes sense. You guys are great.