my '98 f150 currently has a 5" lift with 35's - and i've kept the stock 3:55 gears, it rides fine i think. I did lose some power but it's not too bad. I was looking to put a body lift on and then go a few sizes up in tires - I'm guessing that a gear change will be in order, is 4:10 the right gear? Will i need to do this immediately? thanks

 

With 35's I'd go ahead and step up to 4.56's.

 

Vote #2 for 4.56

 

ok, cool - i'll get that done. Does changing the gears "re-calibrate" your speedometer back to normal? That would be nice.

 

No, you need to change the speedo gear in your transmission tailhousing. There are members here with similar combinations. Ask what gear you need with that tire height/gear combo after you decide definatively on the gear ratio.

 

It won't get the speedo back to the perfect ratio but it will be pretty close because you basically getting different gears to counter the effect of the bigger tires changing your final drive ratio. I would deifinitely go to 4.56. Keeping the stock gears will eventually tear up your tranny.

-Jon