Hi Folks,

Newbie to this forum but excited about finding it!

2002 Duramax, Allison 2500HD.

About 3 months ago, the truck wouldn't shift, shift indicator light went out, auto door locks quit working - traced all back to a bad NSBU.

I bought a replacement and installed it. Fixed all my problems. But...maybe didnt realize it at first, but 'sometime' later, at WOT in 3rd gear, the RPMs would 'freeze' at 2800 (just below redline) and stay in gear until i lifted off the throttle about 15% or so, then it would shift and i could then floor it again.

Been terribly annoying but havent felt like replacing the NSBU again so have been living with not having WOT. Until now...

Coming home last night from the mountains (4 hr drive from the city), i couldnt get past 10%-20% throttle in ANY gear w/out the RPM's 'freezing' and just hanging in gear. Essentially, i couldnt climb any of the mountain passes b/c it wouldnt shift. I had to play with the throttle in various degrees of use in order to feather the RPMs to load to entice a shift. This went on for about an hour, then all of sudden, power is 'cut', check engine light comes on, i'm limited to 65 mph and i REALLY have no power to pass or climb a hill.

Taking it in for a code check (i dont have a reader) but wanted to see what was out there.

Thanks, in advance, for looking!

Change your fuel filter. She's plugged.

Yep, change the fuel filter and report back. Most of the time that is it.
No more than 10K on one.

Plugged fuel filters do the strangest things........................;)

ditto on fuel filter

fuel filter

Wouldn't hurt to change the spin-on filter on the Alli either.

maybe a fuel filter

so these filters usually have to be replaced every 5k on average?

my truck locks me out in the same manor, it will not let me over 2000rpms, witch limits me to about 65mph, but it usually after some miles on my filter, i think i have other issues going on though

Any chance you could have gotten some raunchy diesel and it is clogged up? It's a cheap solution. If neither of these works, then you know it's something more.

so these filters usually have to be replaced every 5k on average?

my truck locks me out in the same manor, it will not let me over 2000rpms, witch limits me to about 65mph, but it usually after some miles on my filter, i think i have other issues going on though

You should be able to get 10k out of them. I just change them every time I change oil.

Well, its taken a while, since its been fricking snowing every other day here, but i changed the fuel filter and VIOLA! she runs great! no more goofy RPM issues, shifting issues or anythign at this point!

a great big thank you goes out to everyone who responded!!

Hey man, glad to hear you got her figured out.