03 Allison

[Vasbinder]

I just bought a 03 GMC Duramax when I leave from a stop and get on it the trans doesn't want to shift. It well hold a gear at 2500 or 2600 RPM till you back of the throttle and it will shift. It's like it has no power and I don't see no codes.

 

[fast03]

change the external filter and since the truck is new to you, change the internal filter also. I am sure others will have more tips.

 

[TrentNell]

i would change the fuel filter also it explains the lack of power and the alli will hold shift when a lack of fuel is present.

 

[stroke250]

x2 fuel filter

 

[Mike L.]

Fuel filter