Engine/Transmission (1998.5 - 2002) Transmission Issue?

[wyatt1672]

2001 4x4 2500 3. 55 gears 268k miles automatic trans. I bought the truck brand new. I have had minor transmission repairs but otherwise the transmission is the original. This truck is not my daily driver. I have been driving on more of a daily basis recently. I have noticed that the trans. will not shift into 2nd gear tell I reach around 25mph at 2200rpm. This is a smooth steady exceleration with no load. Is this normal? The only thing I can think of that I did to the truck before I noticed this was while doing some front brake work I had to resort to heating the axle nut in order to remove it. I had forgotten to remove the speed sensor behind the hub. It did not appear to have any damage. Thoughts, Ideas, Opinions?