I have a 2005 Suburban that I recently purchased and the speedo started making a buzzing noise, so I ordered a rebuilt IPC from digital dash solutions. I put the new one in and it was making the same noise. I have owned a 2003 Suburban and a 2004 Silverado and neither of them made this noise ever, combined ownership mileage over 170k. So I send the new one back and he sends me another one. I put the latest one in and it seems to be working fine and the truck is in 2wd. Then I push the auto 4x4 and it starts making the same noise from the speedo that the first two IPC's made. So I re install the original IPC and it does the same thing. Minimal or no noise in 2wd and noise in auto 4x4, 4hi and 4lo. Switch it back to 2wd and still makes noise until you come to a stop. Any ideas would be greatly appreciated.