Chevy/GMC 2500HDs are popular heavy haulers, especially with the Duramax/Allison drivetrain. These 3/4-ton Chevys ride higher than their K1500 1/2-ton counterparts, but a highway-friendly stance off the assembly line can leave them a little low for off-road performance.
Superlift has offered a 7-inch "bracket-style" Chevy 2500HD lift kit since shortly after the platform was introduced in 1999. The bracket system is a proven performer that fits up to 37-inch-tall tires. Its only drawback is the number of parts, which makes installation a 10-hour-plus job (even for pros) by the time the torsion bars are adjusted and the wheels are aligned.
A plasma cutter makes the quickest, cleanest cuts. A torch or reciprocating saw will also work, but they often require some cleanup grinder work. | 
The kit's skidplate ties together the two crossmembers for added strength and also protects the differential's aluminum housing. Button-head bolts look clean and maximize ground clearance. | 
The kit includes a reinforcement plate that must be welded in place. Superlift recommends temporarily installing the new front crossmember and tack-welding the plate in place to ensure proper clearance, then removing the crossmember for final welding. |
Superlift recently introduced another kit, which includes many of the still-available bracket system's features but adds replacement knuckles. The main benefit is that the knuckles save substantial installation time by retaining the factory steering system and leaving the upper control arms in their stock locations. Superlift's proprietary nodular-iron knuckle castings only increase front track width by 1.8 inches per side. This is necessary for wheel clearance, but some manufacturers' knuckles add up to 6 overall inches to the front track, which is already wider than the rear from the factory. Handling suffers and components become more stressed as the front track grows. (Superlift's bracket kit retains factory front track and allows retaining the stock wheel backspacing.)
Both systems use laser-cut, 0.25-inch-thick plate steel and DOM tubing for load-bearing components. Ride quality and handling are kept stock-like by retaining the factory torsion bars and rear leaf springs. Ride can be stiffened by using a heavier-rate GM torsion bar.
The basic knuckle kit follows the great-bang-per-buck theme Superlift's become famous for. HD owners who want to go even further can choose among many options. These include the TruSpeed speed correction box for larger tires, a steering stabilizer, a stainless steel skidplate, and a choice of two upgraded shocks: Superide Select (SS) Bilstein monotubes or SSR monotubes with remote reservoirs.
Knuckle Notes
Superlift offers its Chevy 2500HD 6-inch knuckle kit for '99-'07 4x4 applications. Superlift recommends professional installation since specialized tools and some welding and cutting are required. Also, trimming the corners off the front valance is all that's necessary to fully clear 35-inch-tall tires.
Two people and a jack are helpful for raising the differential into position. The new upper mount attaches to the front crossmember, and the passenger side's mounts to a plate-steel bracket. This lowers the diff to retain CV axle angles and also "rolls" the housing so that the OE front driveshaft will still work. | 
A Superlift relocation bracket replaces the mount that was cut off the housing; it attaches to the differential via existing bolts. The mount's urethane bushing is lubricated prior to assembly, and a torque wrench should be used for final fastener tightening. | 
The differential's driver-side upper mounting ear must be trimmed off for centerlink clearance in its new location. Heat can damage the aluminum housing, so the job is best done with a reciprocating saw, a cutoff wheel, a hacksaw, or a portable bandsaw - not a torch. |
Nonstock wheel backspacing is also required for knuckle clearance (although the OE spare can be used in an emergency). Backspacing must be between 4.625 and 5 inches, and wheel diameter must be a minimum of 16 inches (to clear the front calipers). 4x4 applications with the OE single exhaust will also need a rerouted crossover pipe to clear the front driveshaft.
The photos here show highlights from the Superlift R&D department's quality-control fitment session. With photo delays, the job took pros Scott Lee and J.P. Pritchard a full day. Ace-wrench home mechanics who are considering doing the installation themselves should set aside substantially more time and use a vehicle hoist if at all possible.
The upshot: a 2500HD that rides high on tires up to 35x12.50. Cargo-carrying capacity is unaffected, and ride quality remains close to stock.
The front suspension and differential are removed; the upper control arms can remain in place. Next, the frame must be trimmed at the driver-side lower differential mount. After the undercoating is removed, a line is scribed per the diagram in the kit's instruction sheet. | 
The Superlift knuckle (left) has a longer neck to compensate for the greater distance between the two control arms. It also has a raised tie-rod boss for steering correction. The factory dust shield is discarded, and the rest of the OE hub assembly is moved to the new knuckle in exactly the same orientation with thread-locking compound applied to the bolts. | 
The diff's mounting bolts are left loose so that the housing can be aligned with the Superlift rear crossmember. This member attaches to the factory lower control-arm holes. |