NP231 Transfer Case for 1987-1990 Jeep Cherokee, Commanche, w/ Slip Yoke Eliminator Kit

Description

Anchoring short mainshaft slipway traction, New Process NP231 SYE Marine Gearbox units deliver mechanical gear reduction with a 2.72:1 low ratio for 1987 to 1990 Jeep Cherokee and Comanche trucks. Rated for 260 continuous horsepower with a 5,000 input RPM ceiling, this fixed-yoke transfer case stabilizes driveline loads when retrieving watercraft on steep ramps.

High-tensile die-cast aluminum forms the split transfer case housing, dampening driveline resonance while minimizing vehicle tare weight. Carburized 8620 alloy steel helical planetary gears provide high-ratio torque multiplication, while an upgraded 32-spline mainshaft eliminates the factory slip yoke. High-capacity needle and caged roller bearings absorb combined radial and axial thrust. The 1.5-quart automatic transmission fluid capacity circulates via internal oil pump galleries, maintaining fluid film protection under continuous towing.

Key Features of New Process NP231 SYE

Shipyard fleet mechanics buy New Process NP231 SYE marine gearbox packages to maintain dependable four-wheel drive power transfer on slick harbor slipways. This transfer case splits rotational torque between front and rear driveline axles during demanding boat retrieval movements.

• 2.72:1 low range gear reduction delivers massive pulling torque on steep slipway ramps
• Heavy-duty slip yoke eliminator kit shortens mainshaft length to optimize rear driveline angles
• Fixed rear companion yoke prevents driveshaft pull-out during steep ramp articulation
• New Process NP231 SYE components maintain planetary gear alignment under shock torque
• Manual floor shift linkage ensures positive mechanical engagement without electrical failure
• Internal fluid pump maintains continuous lubrication across mainshaft roller bearings
• High-capacity Morse drive chain transfers front driving torque without elongation
• Front companion flange connects straight to standard 1310 series universal joint yokes

Slip Yoke Eliminator Mechanics

Operating under medium commercial duty ratings, this transfer case manages 1,750 lb-ft of continuous input torque at 2,200 driveline RPM. The 2.72:1 low range ratio produces tremendous wheel torque while holding transfer case sump operating temperatures between 155°F and 182°F under full load. Heat dissipation across the ribbed aluminum casing reaches 2.3 kW during protracted four-wheel drive ramp work. Planetary helical gear profiles ensure uniform load distribution across tooth flanks, preventing tooth shearing under full engine acceleration.

Fixed Rear Yoke Tolerances

The fixed rear output companion yoke connects straight to 1310 series universal joint driveshafts. Heavy-duty internal needle roller bearings support up to 3,400 pounds of continuous driveline thrust. Dial indicator alignment inspection on the rear output flange face must demonstrate less than 0.002 inches radial runout relative to the mainshaft centerline.

Transfer Housing Service Protocols

Check automatic transmission fluid levels through the upper fill plug port prior to engaging four-wheel drive modes under load. As an explicit negative filter, this truck driveline transfer case is not engineered for direct inboard commercial vessel propulsion shafts or marine winch drive drums.

• Inspect transfer case fluid level and casing joint integrity each shift before boat ramp operation
• Examine shift linkage pivot bushings and fixed yoke seals every 250 hours of fleet use
• Drain Dexron transmission fluid and clean internal oil pump pickup screen every 12 months

Commercial Limited Warranty Roster

Each transfer case unit includes a 1-Year commercial limited warranty against material and manufacturing defects. Crated package contents contain the fully remanufactured transfer case unit, pre-installed slip yoke eliminator kit, front companion yoke, fixed rear yoke, and comprehensive installation instructions manual.