Hey all , changed out 4.10 gears to 3.73s for a little more mpg at road speed . can I recalibrate spedometer with my powre pup or go to dealer. Thanks:

 

what are you going to do with your gears? Would you sell them???

Brad

 

What are you going to do with your 4:10's?

 

I'm going to hold on to them for a few weeks as i do tow some tailors up to 10000 pounds and make sure the 3.73s hold out ok on steep hills. so far it feels great. when i' msure about the 3.73s i'll sell the 4.10s.

 

The 3.73s tow great in that weight range, you'll be selling soon.

 

You are most likley right that i will sell them soon so far the 3.73s are great. I don't know why they can't send more drw out with them . Seem to tow just as well up to 15000 asthe 4.10 . When I was looking for my truck I could not find 1 3.73 . Any one know any thing about calibrating the speedo. Thanks .

 

doesn't the speed sensor pickup off the carrier? if so I don't think ya changed that, speedo should be right on but your rpm will be down and mpg might be up

 

You can change gears to any of the avail and it won't change a thing for speedo calibration. It's the tire size issues that screw things up.

 

I think the ultimate towing machine would be a manual tranny and 4:10 gears, BUT, if you have an auto you'll be glad you changed. My last truck had 4:10's, auto, and 315 tires and it towed terrible. My 04 has 3:73's, auto, and 315 tires and tows great.

 

Could you elaborate on that? Were shift points the problem, or what. Your experience goes against pretty much anything I have heard about gears and towing.

 

I think if you change gear ratios you will have to recalibrate the speedometer. Any change that affects the final drive ratio should affect the speedometer. When I changed from the stock 265 tires to 285s the dealer had to reprogram the computer for the different ratio. I don't think the computer can tell what rear end ratio you are running, it has to be programmed into the computer.

I haven't worked on any vehicles in a lot of years and a lot has changed since I turned any wrenches so if I am wrong I am sure someone on this forum will be glad to set me straight.

 

Where exactly on the rear is the sensor placed? if it was on ring or pinion i don't think it would know that the axels were spining faster than they were with the 4.10s . If it is after the ring and pinion it , such as the outside of the diff or the axels it would know they were spining faster ? anyone know ?

 

Joe N is right, you will have to recalibrate the ABS module for the correct gear ratio. The sensor is on all 4 wheels. Its the wheel speed sensor and it takes into account:

tire size
trans gear ratios
rear gear ratio

How much did it cost and where did you have it done at? They didn't offer a core charge? I think alot of people would be interested in doing the same way (both ways too).

 

Hobbes2 Do you have a good # on the mpg improvement with the 3.73 over the 4.10?

 

What's involved in going from 4.10 to 3.73. I don't care much at all for 4.10 and would consider swapping