Ringing in Duramax diesel with Allison

[hevmando]

I just bought a 2006 GMC 2500HD 6.6 Duramax with 6 spd Allison.  Very happy with the truck but have noticed a ringing noise when it shifts from 1st to 2nd, and 2nd to 3rd.  Last for about 1/2 second and sounds like a bicycle bell.  Anyone have experience with this?  Also it is getting 11-12 mpg on 90-10 wintermix.  I have read about a new chip, an egr block, pcv reroute, and new exhaust.  If anything, I baby this truck and was wondering if there is an easy/relatively inexpensive change to improve mpg. 

 

[Shady Lane]

Are you only getting 11-12 mpg empty? Unloaded miles?

 

[FutureBreeder2013]

There are plenty of tuners and monitors that can help save fuel economy and increase power.

 

[vc]

I had a ringing noise for a while it was a exhaust hose flange or something like that. It would only do it at certain RPM's I thin it was around 17 hundred would not do it anytime else, right RPM right Vibration. It was not big deal, did not hurt anything just bugged me, they fixed it.

We have an 05 it gets 15-16 in the city and 18-20 on the highway (No trailer) with trailer it is around 14-16 I would think you might want to get it checked out.

 

[hevmando]

11-12 mpg city driving 7 miles to work each day.  Got the same going 65mph down interstate with trailer empty, and back with one 800 lb Walks Alone steer on the return trip  460 total miles.  He breaks behind the shoulder slightly but pretty nice otherwise.

 

[rtcc]

Just went to a 06 also, and I hate it, terrible mileage, have had it on computer several times and comes back with no trouble.  Make sure you dont put after market or bigger wheels and tires on the truck, that will cause the tranny to slow down faster then the engine, and that will cause a high pitched ring in the tranny

 

[oldwood]

had an 03 3/4 ton avg mpg was 15, have an 07 dually quad cab was 11.2, put 4 inch exhaust, cold pack and diablo chip set on economy mpg now 13.4, overall cost 1,200 have saved more than that in fuel, the ringing is probably a little heartburn from all the ford and dodges it has sucked up and spit out the tail pipes over the years.LOL

 

[Shady Lane]

I would check the clamps on your intercooler boots as well as the hoses for a small pinhole.

Does the noise come when it is under higher turbo boost? (IE accelerating etc?)

If so it could be compressed air escaping somewhere from the turbo/intercooler setup.

 

[hevmando]

It occurs about 1700 rpm, accellerating and decellerating.  Seems to be more prevalent when warmed up, after been driving for 1 hour or so.  Talked with tranny shop, of course would not do it consistently when there, but both owners have these trucks, 03 and 01 version and told me this, since could not diagnose noise. 1) don't baby it, drive it, as lugging it soots it up and lowers mileage.  Did this on way home and mileage steadingly improved 3/10 on dic.  2) go to 5" exhaust or at least cut out catalytic conv. and change to higher flow muffler.  Deciding on this.  3) Change air intake, to allow more air in now that more air will exit after changing exhaust.  4) put a chip in it from Edge or PPE  5) Then if still not satisfied change trucks or look into egr block and pcv reroute.