im gonna advise you to get your cp3 tested. mine does the same thing when i romp on it. it will rev somewhere in the 2500 -3000 and not change. does this in any gear tho. pulled codes and had p1093 and p1094. took it to mechanic they scanned it and did some testing and "voalla", the injection pump is weak. So I think i would check there also..

 

Ok I will have it tested, when I posted this thread I think it only happend in 4th but now it is through every gear and doesn't want to shift. Now it bogs and runs at 2500 to 3k rpm in every gear until I let off. Or if I stay on the gas it will shift but very hard.

 

some fuel filters can be bad causing reduced fuel flow but fuilds on trans are suppose ot be changed every 50-100k miles! hope this helps!

 

Ok, thanks for all the help guys I was talking to a mechanic and he said it might be a trans sensor because I have an allison.

 

Hey guys changed the filters and fluids in my truck yesterday, It runs like a brand new truck It shifts great and has tons of power!!!

 

Good to hear!!
Sent from my Droid

 

my truck did exactly the same thing. changed the fuel filter and cleaned the mass air sensor just to be safe just this afternoon and it works now try it out all in cost me $80

 

Hey guys I just have a quick update on my truck, after running the truck for awhile it did the same thing again but it turns out it was the alternator, replaced it runs perfect!

 

alternator causing it to not shift?? Im not buying what your selling, my bet is that you still have issues, did you change the transmission oil?? was it burn? were there a lot of black or silvery flakes? did you remember to save the magnetic washer on the spin on filter?

if its "flaring" im not buying that its fuel filter or alternator or anything BUT the transmission

 

I know it sounds crazy but the trans needs 12 or 12.5 volts to the comp for it to tell the trans to shift right and when the alternator went it was useing all the volts for all the lights my truck was running, it would run better in the day when I shut the lights off. And yes and changed all the fluids and the trans fluid was alittle burnt but did not have any shavings in it. The truck runs perfect now and I have not had any trouble since I changed the alternator, I know its weird but it fixed it.