Odd noise from behind dash

Billyjack · Oct 12, 2025

Hello! I ava a 2001 GMC 2500 SLE, with the 6.0 engine. I have an odd, grinding/whining kind of noise coming from behind the dash, kind of like near the climate control area. It only occurs under acceleration up to about 1,800 rpms in first gear. Almost like a worn out tach/speedo cable would sound on an older car.

Anyone else experience anything like this? Thanks!

ORVietVet · Oct 12, 2025

Does the noise change at all with any changes to the HVAC controls? Does it sound different with hood open or closed, when power braking?

Billyjack · Oct 12, 2025

ORVietVet said:
Does the noise change at all with any changes to the HVAC controls? Does it sound different with hood open or closed, when power braking?

It occurs regardless of HVAC settings. I have only experienced it while driving, but to be honest I haven't tried it in neutral, which i should do. But it only seems to occur in first gear, not second, as the rpms climb from about 1500 to 2000. I should also say sometimes its louder than other instances. Could it be something in the gauge assembly?

ORVietVet · Oct 12, 2025

Doubt if in gauges. Do any of them change or act funny when noise is happening. You can try neutral but I think a power brake may duplicate. Noise could be from exterior firewall area.

Billyjack · Oct 12, 2025

ORVietVet said:
Doubt if in gauges. Do any of them change or act funny when noise is happening. You can try neutral but I think a power brake may duplicate. Noise could be from exterior firewall area.

I'll give the powerbrake a try. The sound seems like its coming from right behind the radio/hvac area.

Billyjack · Oct 12, 2025

Billyjack said:
I'll give the powerbrake a try. The sound seems like its coming from right behind the radio/hvac area.

In neutral, no noise. Powerbrake produced some of the noise. It could also be coming from directly behind the speedo?

ORVietVet · Oct 12, 2025

Did you do the power brake with hood up AND down, to see if there is a difference?

If you have a trusted friend, get them to power brake and you listen at the engine side of firewall and see if you can pinpoint. May be from transmission bell housing.

Billyjack · Oct 13, 2025

ORVietVet said:
Did you do the power brake with hood up AND down, to see if there is a difference?

If you have a trusted friend, get them to power brake and you listen at the engine side of firewall and see if you can pinpoint. May be from transmission bell housing.

I'll give that a try. If its bellhousing (because it could also possibly be coming from the trans tunnel), what would be the nature/solution regarding that?