Odd noise at 30mph

[illwood]

Figures, just after I install my AVIC-F90BT from John's Stereo, my Marauder gets a funny noise. It seems to happen around the 28-32mph range when it am at 25% throttle or less (this is assumed, not datalogged). The sound is about 1/2 second long, followed by a 1/2 second of silence and so on (you can feel the vibration almost like driving over those grooved sections in parking garages). The best description I can give is dragging a saw blade over a 2x4 (with a little more bass). The parking brake does not appear to affect the noise (already replaced the shoes on one side). The sound seems to be drivetrain related and I'm not quite sure of it is front or rear.

I'm presently at almost 80k miles, back to running a stock tune (to get a little more mpg), and I have new rear tires (2 weeks old) and a full balance and alignment at the time.

I could use some help diagnosing this one.

Thanks!

[Zack]

Cant help you with the noise, but I can tell you you will get Better mileage with an aftermarket tune loaded.

[SID210SA]

I dont get better gas milage in city driving with the tune in....I do get better milage with the tune in with hwy driving....so I am also currently driving with out the tune in.

[illwood]

Cant help you with the noise, but I can tell you you will get Better mileage with an aftermarket tune loaded.
Because of the road that I drive on with my daily commute, I need the converter to lock into overdrive no later than 40mph. The stock tune locks it at 35mph and the Lidio tune doesn't lock it until 65mph. I may see what I can do about getting a custom tune to take advantage of a better spark/fuel mapping, but I can't argue with getting 23mpg on a tune and 26mpg on stock for now.

[Bradley G]

SAME HERE ,the N/A tune on the GMQ won't let the converter lock up until the vehicle is near highway speeds. I am down 1-2 mpgs with the tune, still gets excellent mileage 19.48 city last tank.
Your noise sounds trans related, maybe you drop the trans pan and take a look.
Seafoam makes a product (additive)especially for transmissions.


quote=SID210SA;646062]I dont get better gas milage in city driving with the tune in....I do get better milage with the tune in with hwy driving....so I am also currently driving with out the tune in.[/quote]

[Aren Jay]

I have to wonder about this city driving being different from highway driving. We have big fast roads here in town, very few slow roads unless your in an area driving to your house, which is usually only 3 or so minutes away from a fast road.

As for this noise. Is it from the dash? is something loose, did you forget to tighten a screw or miss a screw?

Does it happen with the audio mute on? or the Stereo off?

Did you try driving in 1st gear only and see if it makes the sound, how about 2nd only? Does turning effect it...

We need more info.