just bought a duramax ('05) in august. ran a little different than I'm used to with the automatic but dealership said it was the tranny learning my habits.

for the past month or so, the engine will pull to 2500 rpm when cold and won't shift till I let off the throttle. once it's warm it'll rev to 2000 rpm and fall on its face till I let off the throttle. I thought it might be a batch of bad fuel so I went to a different station this a.m. and she continues to do the same thing.

fuel filter life indicator suggests 40% life left. could it be clogged or something? please don't tell me it's tranny related.

no check engine or service engine soon lights or anything. all pressures/temperatures/fluid levels appear to be normal.

what should be my first action? change fuel filter? or take to dealership right away?

If you are under warranty, I'd have the dealer handle it.

However the 2000rpm "limit" is normally associated with engine codes, with the most common being P1093, which can sometimes mean just a dirty fuel filter. It is MUCH cheaper to do it yourself, and is not that hard.

So if you do not know when the filter was replaced for a fact, you should replace it. That's what the dealer will do 90% of the time, and charge you about $150 parts and labor, whether it solves the problem or not.

Check the level of your trans, and change the "spin-on" filter.

If you are under warranty, I'd have the dealer handle it.


ditto.. take it in and let them troubleshoot it.

just bought a duramax ('05) in august. ran a little different than I'm used to with the automatic but dealership said it was the tranny learning my habits.

for the past month or so, the engine will pull to 2500 rpm when cold and won't shift till I let off the throttle. once it's warm it'll rev to 2000 rpm and fall on its face till I let off the throttle. I thought it might be a batch of bad fuel so I went to a different station this a.m. and she continues to do the same thing.

fuel filter life indicator suggests 40% life left. could it be clogged or something? please don't tell me it's tranny related.

no check engine or service engine soon lights or anything. all pressures/temperatures/fluid levels appear to be normal.

what should be my first action? change fuel filter? or take to dealership right away?

First thing for sure...
Even so, if you don't know the maintenance on the truck, you should change all the fluids and filters so you are in control of your maintenance schedule. In the end, cheap insurance.

I was told you can take the truck to 55 mph, and then slam it into first gear. Let it coast all the way to a complete stop. I believe you do this 3 times? ANYONE?????
Once you do this, the tranny will programmed be as stock and begin to learn your habits.

Also, make sure you are not in Tow mode and that you are in 2 wheel drive.
Silly as it may sound these things get overlooked sometimes.
You might press the tow mode button and see how it shifts then. Maybe the light is burnt out?
Again simple things that come to mind, since it sounds like it is shifting as if you were towing.

Anyone chime in if this is incorrect information.

I bought it new (well, 5 miles on it anyway) and I changed the oil but have not changed the fuel filter yet. got 9k miles on her now. you think I should change the fuel filter prior to taking it in? how difficult is that? I change the oil on my car but I've never changed fuel filters before.

I bought it new (well, 5 miles on it anyway) and I changed the oil but have not changed the fuel filter yet. got 9k miles on her now. you think I should change the fuel filter prior to taking it in? how difficult is that? I change the oil on my car but I've never changed fuel filters before.

There is a DIY thread you can go to. The hardest part is breaking it loose. The factory "glues" them on....After that, the procedure is simple and as easy as changing oil. easire maybe.
Found it.. http://www.dieselplace.com/forum/showthread.php?t=1508&highlight=fuel+change+diy

I also posted a few alternative methods, such as going through the wheel well, if you are tight on top. It was met with mixed feelings. Photos posted there too. http://www.dieselplace.com/forum/showthread.php?t=75646 The reason I do it my way is that I have very limited clearance due to A/C lines sticking out further than most, and I choose not to bend them, when I can easily go through the fender well. NOTE> Cover the filter with plastic when doing this to prevent dust and debris from getting in. I do this either way I go in. Stuff gets knocked loose, and why have it in your important filter?

Also, McRat is right, let them deal with it, but they will still charge an arm and a leg to change it, and they will likely change it as part of the diagnostic. No change then you have to fight not to pay.

thanks for the input!

update--took her into the dealership this a.m., the scanned for codes/updates. no updates available at this time but showed 2 fuel filter codes so they said change it out and get back to them if the issue returns.

thanks for the input guys.:)

I have been having similar problems with my 04.5 LLY. I've got an edge set on level 4, 5" exhaust and an intake. It will set the world on fire from 1st-4th but as soon as it hit 5th it falls on its face. The truck won't accelerate even pushing the pedal to 3/4 throttle then it drops to 4th and takes off again. I have changed all fluids and filters. It acts like it wants to keep accelerating through 5th as well but won't. Another issue is once it stays in 5th gear for about 45 sec or so (keeping in mind no further acceleration but pressing the pedal down to accelerate) out of no where the power kicks in and it takes off. Its almost like there is a delay in the programmer. HELP!!

I have been having similar problems with my 04.5 LLY. I've got an edge set on level 4, 5" exhaust and an intake. It will set the world on fire from 1st-4th but as soon as it hit 5th it falls on its face. The truck won't accelerate even pushing the pedal to 3/4 throttle then it drops to 4th and takes off again. I have changed all fluids and filters. It acts like it wants to keep accelerating through 5th as well but won't. Another issue is once it stays in 5th gear for about 45 sec or so (keeping in mind no further acceleration but pressing the pedal down to accelerate) out of no where the power kicks in and it takes off. Its almost like there is a delay in the programmer. HELP!!

You most likely need a "shim mod". Do a search.

after finally changing the fuel filter the truck is running normal again. thanks for the input guys.

Sounds like you are slipping 5th gear. The allison is known for a relatively weak 5th.

edge on level 4=running out of fuel.add a lift pump.then a trans