allison 6th gear noise

[notslo]

I have a 2003 journey, cat 330, allison 6. It has about 18000 miles, had the trans serviced at 6000 miles. In 6th gear at 1500-1650 with half or more throttle there is a resonate drone coming from the trans ( I think ). Same road speed in 5th or same rpm in 5th is quiet. Anyone else have that. I am on my first long trip and prior to buying did not have any roads that 6th could be used for any time.

[notslo]

I have a 2003 journey, cat 330, allison 6. It has about 18000 miles, had the trans serviced at 6000 miles. In 6th gear at 1500-1650 with half or more throttle there is a resonate drone coming from the trans ( I think ). Same road speed in 5th or same rpm in 5th is quiet. Anyone else have that. I am on my first long trip and prior to buying did not have any roads that 6th could be used for any time.

[Chief]

Don't have any experience with this noise, but it sounds like it could be a "harmonic". If you haven't done so allready, I would check to make sure the ride height adjustment is correct. Hopefully someone will chime in with more knowledge. Good Luck.