I was wondering if anyone with the 5.4L and the auto transmission has swapped out their 3.73 gears to 4.56. And that have not reprogrammed their computer with a superchip programmer or other programmer. I have heard of a few people that have and I was wondering if you had any problems with the truck like for instance the overdrive not working properly. Or anything else that came up due to not recalibrating the speedometer. Your responses are greatly appreciated. Thanks, I have my gears and I am ready to install them but the superchip programmer will not be in stock untill next week.

 

Changing gears, and not the appropriate speedo, should cause you all softs of shifting issues. Are you keeping the stock tires, or going up proportionally? That will have some say in how weird your tranny will act.

 

Well, I am running 37x12.50x17's in the BFG Mud-Terrains. So I believe that the 4.56 gears are what is best for my driving habits and getting me back to stock gas mileage and towing and power when accelerating. I am just wondering about the auto tranny shifting issues. My tech told me that the overdrive might not work properly since the computer is calibrated to the stock gears. Will this cause a problem if I dont buy a programmer? Thanks for your help.

 

Oh, well if you currently have 37"s, your tranny should shift a hell of a lot better than it does now. How does your tranny shift now with that combo? I cannot definitively tell you that everything should work right, but I do know that your setup wont match OEM spec perfectly, so I would expect some anomalies. Personally, I would get a programmer, to eleviate any concerns. Although you might not feel any weird shifts with leaving it stock, there could be more work having to be done 'behind the scenes' that might put more wear and tear on the tranny.

 

The tranny to me seems to shift ok other than I only get 285 mile to a tank of gas and I drive 30-35 miles to and from work 5 days out of the week. And I have noticed that i did lose some take off power and some top end power. I also pull a 21 foot boat and I notice a big difference since I installed the 6 inch Skyjacker lift and the 37's. Do you think that going with the 4.56 gears and not reprogramming just yet will do some damage to my tranny?

 

Outright damage? No. What I meant was, since these new trucks are almost completely computer controlled, if some of the tranny sensors arent reading "spec", they might try and work around that, to keep the truck moving as if it were stock. If you dont notice anything weird now with it, chances are you wont notice anything weird with the swap.