Allison 5th & 6th Gear Noise

[DarylB]

Hey guys,

I've got a 2007 Classic Crew Cab 4x4. Love the truck, but at 55-60mph in both 5th and 6th gear (approx 1400-1600 rpms) I get a bad howling/grinding noise. The best way to describe is is a "lugging" sound like when you lug a manual in too high a gear then try to accelerate. Any ideas? My 2002 LB7 didn't do this in 5th, ever, but the new truck does it some in 5th, but a lot in 6th.

[More Power]

What's the dealer say about it? Does it do this when the trans is cold? The TC doesn't lock till the trans approaches operating temperature. I wonder if this is TC related?

Jim

[DarylB]

I haven't talked with the dealer about it yet, the truck only has 8300 miles. It does it all the time, cold or full operating temperature. I was gonna do some research first to see if there was a known issue. My old 2002 was an Ext cab 4x4, this one is a crew. The 2007 has a solid, 1 piece driveshaft, big aluminum. At least 1" bigger in diameter than the 2002. The vibration/noise can be felt in the floorboard, almost like the planetaries are grinding or it's in the T-case. It's almost like a rough-bearing noise, but only occurs intermittently in the OD gears, at specific RPMs