Allison 1000 Transmission Transfer Case Brace, 01-07

The aluminum tail shaft adapter housing that sits between an Allison 1000 and the transfer case on 2001-2007 GM 4x4 trucks is a known crack point. The transfer case hangs off the back of it as dead weight, and every bit of driveline vibration, every hard launch, and every washboard road works that cantilevered load against a thin casting. When it lets go you get an ATF leak first, and if it is ignored long enough, debris and fluid loss take out the transmission and the case with it. Fixing a cracked housing means pulling both the transmission and the transfer case.

This brace, PPE part number 129020107, takes that load off the housing. Two 304 stainless 7/8 inch support tubes run forward from the transfer case and tie into a thick 304 stainless plate, spreading the weight up and across the adapter and into the center section of the transmission instead of letting the casting carry it alone. Stainless means it does not rust out from road salt where it lives.

It bolts on from underneath with the drivetrain still in the truck. No transmission or transfer case removal, no special tools. Fitment is 2001-2007 GM 2500HD and 3500 pickups with the Allison 1000 and a factory transfer case, which covers LB7, LLY, LBZ, and 2007 LMM Duramax trucks. It is a preventive part first and foremost, so the time to install it is before the housing shows a seep, and it is a standard piece of prep on any truck that tows heavy, runs offroad, or makes more than stock power.