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Our Wildwood, FL techs will confirm the right part for your build before you buy.
Call or Text (352) 722-5295Wiring and ball hardware on the Sierra HD LMM
Start with what the factory wired in. A trailering-package Sierra has a sealed 7-way at the bumper and a brake-controller jumper waiting for a controller, and GMC also offered an ABS-integrated trailer brake controller from the factory. Order the camper, fifth-wheel and gooseneck wiring provisions and the truck got an 8-way harness that runs to the front of the box. The ball side starts at the 2.5-inch receiver, which came with a 2-inch adapter. Whether it's a WT on a job site or an SLT hauling a camper, the LMM 6.6L Duramax and Allison six-speed do the pulling. These accessories make the connection.
What to check before you buy
There's no known failure pattern to report for these accessories on the LMM Sierra. The trouble is mismatch: a ball that's the wrong size for the coupler, a shank that's loose in the ball mount, or a trailer plug that doesn't fit the truck's socket. Check three things before you order: the ball size your trailer coupler calls for, the hole diameter in your ball mount, and whether your trailers use a 7-way or a 4-pole plug.
Factory hardware vs. replacement
GM's factory items on these trucks are the sealed 7-way, the brake-controller jumper and, on trucks with the provisions, the 8-way bed harness. The ball and any sleeve it needs change with the trailer, so that's the hardware a Sierra owner ends up buying and swapping. On the electrical side, the BHP4002 is the replacement-style piece: a socket with 7-way and 4-pole connections on its own mounting bracket, handy when the original is damaged or when a 4-pole utility trailer joins the lineup.
What we carry
- B&W Trailer Hitches BW-THB hitch balls
- B&W BW-RE-SL reducer sleeves
- Big Hitch Products BHP4002 7 & 4 Pole Trailer Connector Socket with mounting bracket, listed for 2001-2025 6.6L Duramax
Receivers, ball mounts and weight distribution live in hitches.
Fitment notes
Box length matters under the bed: standard-box and long-box Sierras route the factory fifth-wheel wiring differently, so check which box you have before buying bed wiring parts. The BHP4002's listing covers 2001-2025 6.6L Duramax trucks; still run it through the fitment checker for your year. Balls and sleeves fit the ball mount, not the truck. 2007 owners should confirm they have the 2007.5 new-body Sierra and not the Sierra Classic, which carried the LBZ. Verify by VIN, or call for fitment help.
Frequently asked questions
Can I plug a 4-pole trailer into my Sierra?
With the BHP4002 socket, yes. It carries both 7-way and 4-pole connections on one bracket, so a 4-pole utility trailer and a 7-way camper can both plug in at the truck.
Do hitch balls and reducer sleeves fit any truck?
They fit the ball mount, not the truck. Match the ball to your trailer coupler and the shank to the hole in the ball mount, and use a B&W reducer sleeve when the shank is smaller than the hole. Make sure every piece is rated for the trailer you're pulling.
Does my Sierra have a trailer brake controller?
Trailering-package Sierras came with a brake-controller jumper, and an ABS-integrated trailer brake controller was a factory option. If you're not sure what your truck has, call the shop with the VIN and we'll help you sort it out.
Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.