Allison growl at 25mph

[ruspoe03]

While in tow/haul, I think at the time the Torque Converter locks (20 to 25 mph), I hear a brief growl sound. Almost sounds like I'm running over a cattle grate or something. Is this something to worry about? Other than this, she runs like a dream.

2003 Sierra Duramax/Allison

[ruspoe03]

Found this while doing research on my question.
Can anyone else confirm the fact that this is normal operation and nothing to worry about?


Sounds like the torque converter locking up. Lock up occurs at about 50 MPH in normal mode and 25 MPH in Tow/Haul. Usually there's a buzzing noise but sometimes you can feel a vibration too. It's most noticeable at low or medium throttle. It's annoying but it's one of the natures of the beast. Some are worse then others but it's nothing to worry about.

[JohnC]

I think it's just that when the TCC locks, more engine vibration is transmitted to the drive line. My wife's '99 5.3 even does it. Only noticable when the engine is "lugging."

[KrazyNate]

Problem here as well. Mine is an 02 and whines pretty good in 4x4 at 1800-2000 RPMs... Ill just drive it until it blows.. Had this pile, I mean dream machine, for two months... Been in the shop 1...2...3... fourth trip... Shoulda NOT bought this one me thinks.....:mad: