I have a 2003 Duramax with allison tranny. When I pull my 35 ft trailer or accelerate fast, the engine makes 2 kinds of noises, one is a rattling noise like a gas engine that has bad gas in it and the other is a rumbling noise. It lasts seconds but does not sound good to me.


I have read about getting updates on my computer on board the truck, is this going to help? How often do they update the computer and what should I ask for. I understand the engine is warrantied for 100,000 miles but having it crap out on me in the middle of East Bum F--k is not what I want to happen if you know what I mean. We travel the east coast when on vacation.


I had a flat tire on Bridgestone V-Steel RIB 265 LT 245/75R16 and it was not pleasant trying to find another.

At 2600 RPM's the pilot injection stops. Engine gets
louder. Pilot injection is what allows the engine to run
quieter. It is in the design of the engine.

COULD be what you are hearing.

Max Owner I hear a lot about this pilot injection thingy which makes the engine quiet. what is it & what does does it do exactly other than quiet down the injectors?


My first thought is that it reduces rail pressure to the injectors and doesn't restore full pressure until it's needed for increased power. Is that it? Thanks

How about the question of when to have computer updated and what to ask for.


The noise- when it happens it sounds like the engine is really crapping out or is about to. How about the decrease in milage I am having. Usually when pulling the rig I get about 11.5-11.7 no matter up and down hills of Vermont or on the staight away of RT90. 1st half of my trip to South Carolina was 11.7 but coming back(when engine got really noisy) went to 10.7 and has consistantly stayed there until I stopped pulling the trailer. Have not seen what I am now getting without pulling the trailer. What do we ask them to look at for the decrease in miliage????

When I started pulling my 5ver for the 1st time that is when I really noticed my turbo kicking in more often. I keep mine in cruise control & when I hit a hill my turbo kicks in & that can be loud if your not use to it. Edited by: Rick&Danni

Don't forget the engine fan coming on also. Makes a lot of noise, mine sounds like a jet sometimes. I wouldn't worry about a 1 MPG drop in mileage. Could have been the wind, lower quality fuel etc. I am not sure if they have any computer updates for the 2003 you might try the "Ask the Tech's" forum here. Fords new 6.0 had a whole pile of computer problems and the earlier Chevys had a few.

I hear a lot about this pilot injection thingy which makes the engine quiet.** what is it & what does does it do exactly other*than quiet down the injectors?*

I read this answer in another post, so I'll give it a shot, IIRC: pilot injection gives a small squirt of fuel just before the big injection gets there. The small amount is already burning when the big burst gets there and softens the ignition explosion. If you get over 2500 RPM the pilot injection kicks out, and you do hear the full diesel knock. Or, as I was told the first time I asked about the noise, it is the sound you hear just before the D/A breaks the sound barrier. http://www.dieselplace.com/forum/smileys/smiley2.gif

Yeah. What he said.

Cooling fan could also be the culprit, like Big Daddy G said.
Makes a fair bit of noise, and draws lots of power. Its normal
for the cooling fan.

At 2600 RPM's the pilot injection stops. Engine gets louder. Pilot injection is what allows the engine to run quieter. It is in the design of the engine.
COULD be what you are hearing.



It also shuts off above a given fuel flow - so under a heavy load and at lower rpms it could start ka-knockin'





- jeff

As long as it does not mean i have bad injectors or that the engine is going to crap out I do not care. BUT if I should report it and have them check the computer I will, just need to know what I ask for.