my next mod is definately going to be new gears. i was wondering on the ratio i should get - 4.10 or 4.30. i have a 99 v6 auto with stock tires and the 3.55 right now. i was wondering also if i need to re-program my computer chip for the gears to work properly. i would also like to know the best shift kit i can get for a reasonably low cost. i plan to keep stock tires so i need to know stuff like : what speed will my truck shift now?ex. my 1-2 shift is at 45 and the 2-3 is at 77. my rpm's at highway speeds. ex. now it is 1900-2000 rpm's@70mph. also any other things i would need to know. my gas bill isnt that important b/c i dont have to drive alot, i just want to get a little faster. sorry for the long post guys but this is big for me!!!!! any help will be greatly appreciated

 

Richard;

If you go to a 4.10, your revs will increase by 15% from where they are now for a given road speed (21% for 4.30). This makes the change barely noticable from a sound perspective in my truck but the power is way better.

I couldn't get 4.30 for my axle combo but probably would have if they were available.

For a shift kit, you might just want to get a superchip - it makes a big difference in shifting and you will need it to correct your speedo after the gearing changes, anyway.

The gearing change was the best change I have made to my truck.

Ian

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99 Expedition EB
5.4l, 4x4, 4.10 LS
WMS Tube, Bassani Cat Back Exhaust, Superchip Flipchip, PIAA Superwhites

 

If you want to do a gear calculation vs. rpm go to this web site.

http://www.4lo.com/

This is a good place to start, since they specialize in gearing for rock crawling machines.