Still struggling to learn the "normal' noises of the D/A. Once
warm my rig humm's loudly once the trans is in O/D (not towing).
It is loudest at 55-60 mph and goes away at an increased speed. It is
present on deceleration until the trans kicks out of O/D.



Does anyone's truck do this?? It's not the fan clutch going
on/off. Not the P/S pump. I guess it could be the turbo but
it is a humm - not a whistle and why is it O/D related (or so it
appears)??



Thanks!



Rob

I'm not an expert, but mine doesn't seem to do that, and it's about the same truck, just a different emblem. I just got back from a 340 mile trip and didn't notice any different noises when in overdrive or not. Might want to take a technician for a quick drive.

it is normal...mine does it and I believe there is another post about this somewhere where others have this same humm or moan

it is normal...mine does it and I believe there is another post about this somewhere where others have this same humm or moan



Thanks - a "moan" best describes it! Sure is annoying sometimes -
other times it doesn't bother me. Helps to know others have
it. Just wish it wouldn't do it at hwy speeds.



Rob

I am not sure if this is related yet but I am going to check my truck. Max payne posted a recent post about "possible fix to loud in cab noise", here is the link to what he said, http://dieselplace.com/forum/forum_posts.asp?TID=17896&amp;P (http://dieselplace.com/forum/forum_posts.asp?TID=17896&amp;PN=1) N=1<?:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />


You are right it sometimes gets annoying and it is between the 55-60 mph ranges. Sometimes I have heard it up to 63mph...

Yea - I looked at that link when it first posted. I don't think
it is the source of the noise. It's too constant of a noise to be
caused by a rattling shield. It definately stops when the trans
goes out of O/D.



On edit: You can feel the slight vibration in the acceleration pedal.


Edited by: skoryaro2

Every GM van/truck I've owned since 81 has had a rear end whine, guess I have gotten used to it. It is more pronounced once the o/d kicks in and usually subsides once your RPM's are up high enough at higher speeds. My new truck has it to, especially after sitting overnight and running with cold rear diff fluid.


You might want to check the rear diff fluid to make sure it is full. Several guys have posted there trucks were about 2 quarts low, system holds just shy of 4 quarts. Otherwise keep your favorite CD's handy and turn the volume up and you won't hear a whisper. JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

JJ,



Thanks, but I already knew about the rear diff level issue. This
isn't rear diff related, definately from the engine / trans

Then CD's it is! A good sub-woofer will help to. Good luck! JJ http://www.dieselplace.com/forum/smileys/smiley4.gif

I'm with Rob, I also changed my rear lube to AMSOIL and yes it was low from the factory but it is up to spec. now

Update - dealer says the noise is normal. Has had a few similar complaints and compared with a new truck on lot.

I'll bet the noise you hear is the same as the one I hear. If it is the same, its normal.


It is rpm related, not speed. I first though it was speed related because I heard it between about 60 and 65 mph. It actually happend around 1800 rpm. It just so happend that on the highway at 1800 I'm usually between 60 and 65. If you get it in that rpm range at a different speed you will hear it.


It is just a resonance, probably from the exhaust. Nothing to worry about. I think it may only be on 2005's but not sure. Would be interesting to see if anyone that had the noise still had it after going to a 4 or 5" exhaust. I'm betting it would go away or shift to a different RPM range.


There is another thread I started a while back about this around. You might be able to find if you search on 'drone'. I described it as a drone.

Mark_My_Word,



Thanks for the feedback - I'm not really worried about it but it's just
a little annoying once in a while. You described it to a
"T". Dealer said he thought it was an exhaust resonance
also. He was going to forward the handfull of similar complaints
that he got to GM for some feedback.

Just another one of those sounds that means POWER! You'll get to love and appreciate them over time...well most of them at least. The hard part is figuring out which ones are o.k. and which are bad. That is where dieselplace comes in!