[TXAustin]

Well it can change greatly on when it shifts depending on how you drive. Mine locks up at EXACTLY 56mph so you are fine there.
Coming from a light mine shifts at about 1500-1700 each time though.

 

[KAS]

Mine will dump in to OD at 50mph on flat ground with a light foot.

 

[TXAustin]

Yes I forgot to add I have 37s. On my buddys with 33's still on the lock up is 47-50mph.

 

[cerberusiam]

Into OD at 55 mph is normal. The OD shift is ECU controlled so there is no real good way other than throttle to influence it.

 

[steelhead01]

sub 17 mpg for 4.10 gears is in the normal range for a 2wdr on winter diesel.
some get better some worse
with the cold winter temps at your location, the local fuel depots are probably dumping 50% #1 mix into the diesel. the stuff has far less energy and mpg

original tranny?
how many miles on it?
get a scan tool or scanner on it and check for transmission slippage.

 

[tex_waco_usmc]

sub 17 mpg for 4.10 gears is in the normal range for a 2wdr on winter diesel.
some get better some worse
with the cold winter temps at your location, the local fuel depots are probably dumping 50% #1 mix into the diesel. the stuff has far less energy and mpg

original tranny?
how many miles on it?
get a scan tool or scanner on it and check for transmission slippage.

I am in Texas and well the temperatures are no where near "cold" but the fuel could be different. As a matter of fact fuel mileage did start to decline when the colder temps came in. It is the original tranny, minus the shift kit and sensors, truck has less than 70K on it and there is no slippage had that checked the other day. I am going to chaulk it up to different fuel. Also, can I change those gears? Recommendations/thoughts?

 

[Ramming Don]

I am in Texas and well the temperatures are no where near "cold" but the fuel could be different. As a matter of fact fuel mileage did start to decline when the colder temps came in. It is the original tranny, minus the shift kit and sensors, truck has less than 70K on it and there is no slippage had that checked the other day. I am going to chaulk it up to different fuel. Also, can I change those gears? Recommendations/thoughts?

You could change gears but I would change tire size personally. I would love to have 4.10's I would run 37's but since I have 3.73's I am only running 35's. Gears can be changed but it is better to pay a professional mechanic to do it and that runs around $250+ for the labor.

 

[Ramming Don]

What size tires do you have now???

 

[tex_waco_usmc]

What size tires do you have now???

I dont know exactly what size they are but they are stock size for a 2wd dually! I have a friend that is a tranny mechanic and owns his own shop so my labor cost wouldnt be that great. I am wondering if 3.73s wouldnt work better for me as I dont tow too heavy too often!?!?!

 

[Ramming Don]

3.73's are a great all around gear, actually one of my favorites. But remember the money you spend for gears, lube and labor, vs. the amount of fuel you will actually save takes along time just to recoup your investment. There isn't really that much difference for me to justify a 3.73 to 4.10 swap. Back to the tires again, you would only have to go up like one inch or so to get the same gearing as the 3.73's. This is just my opinion from building several 4x4's and race cars/motorcycles. Money could be better spent on other mods to increase MPG.:beer