Allison 1000 Transmission Crossmember for Silverado 2500HD

This is the center transmission support crossmember that bolts across the frame under the tailshaft on GM three-quarter and one-ton trucks. It is the Dorman 926-980, a direct replacement for GM part numbers 15904054 and 25814670, and it carries the transmission mount that holds up the back of the Allison 1000 or 4L80E. It bolts in using the factory frame holes with no cutting and no welding.

Fitment covers Chevrolet Silverado 2500 HD 2001-2010, Silverado 3500 2001-2006, Silverado 3500 HD 2007-2010, Suburban 2500 2008-2013, Suburban 3500 HD 2016-2019, GMC Sierra 2500 HD 2001-2010, Sierra 3500 2001-2006, Sierra 3500 HD 2007-2010, and Yukon XL 2500 2008-2013. Confirm your trim before ordering, because the HD frames changed between the GMT800 and GMT900 platforms.

This is the part that rots out first on salt-belt trucks. The stamped channel traps road spray where the mount bolts through, and once the steel thins the mount pulls loose and the whole tailshaft starts moving. You feel it as a clunk on shifts, a driveline vibration that comes and goes, and eventually a cracked mount or a bent cooler line. Shops also hit this on Duramax swaps and on any truck where a previous crossmember was torched out and never replaced properly.

Replacement is straightforward on a lift: support the transmission with a jack, unbolt the mount from the crossmember, pull the four frame bolts, drop the old member out, and reverse. Reuse or replace the transmission mount separately - it is not included. Torque the frame bolts to the factory spec and recheck driveline angle before you set the truck down.