Just got done swapping 4.56 gears on a truck, and now the truck wont shift into OD. Any idea why this might be?

 

On the 99 you have listed in your sig or a different one?

 

No, its on an 06. I need to change my sig, dont have the 99 anymore

 

I'm wondering if you have to change something in the computer to tell the tranny of the difference. It may be you are further into the throttle and the computer thinks the trans is under more load and won't let it upshift. Don't give up, someone smarter than me will be along and probably know right what to do.

 

Check for soft codes, technically it should make no difference the gear ratio because the ABS reads the signal from the ring gear not the pinion. Some trucks will throw a code because the parameters are not matching what it thinks it should and that will mess up the OD.

I take it the speedo is working and CEL is not lit?

 

Yup, everything else is working properly, no CEL, and no codes per a Smarty lookup..