I have a '96 f150 4x4 w/ a 4.9L and auto trans. I am running 33x12.50x15's and feel like I need to change my diff ratio because my engine seems to always be under such a load. It doesn't shift into 3rd till almost 55mph. Thanks for any advice!!!

 

What's your gear ratio now? I had a 300 six and lowering the gear ratio after installing taller tires made a huge difference.

If you have 3.55 gears now, you would want to go with at least a 3.73.

If you have 3.73's, go with 4.10's.

Or just go straight to the 4.10's.

 

It has 3.08 gears in it now, I think

 

Then go up to at least 3.73