So my tranny was driving perfect till today still has full fluid no leaks but its slipping in third gear and overdrive and if you get on it in second. It still moves just not well. It seems to be all done but I was just wondering if theres any sensors or anything that might cause this. Anyone experiance this?

 

A little more info... is this the 03 Duramax with the 1000 Allison transmission???

 

Its the 4.8. Single cab short bed. 130,000 miles. I thought it might be a sensor because the tow/haul button is not showing working and it was the day before

 

Try pulling the tranni dip stick and SMELL it.
If it smells some what BURT I'm sure you can guess what your problem is.