NP246 Transfer Case Schematic and Key Component Breakdown for Repairs

Start by locating the intermediate shaft bearing retainer–its position is critical for proper reassembly. Remove the snap ring securing the rear output shaft flange before disassembling the shifting fork mechanism. The main shaft often requires a puller due to press-fit bearings, while the mode fork should be inspected for wear on the engagement surfaces. Replace the thrust washers if scoring exceeds 0.2mm.

The planetary gear set must be handled carefully; misalignment during installation will cause binding. Note the orientation of the ring gear–the chamfered teeth face the torque converter side. When servicing the front output housing, clean the mating surfaces thoroughly and apply a thin layer of RTV sealant to prevent leaks. Torque the housing bolts in a cross pattern to 25-30 Nm.

For the electric shift motor, verify continuity between terminals A and C–resistance should read 20-30 ohms. If the encoder ring shows signs of wear, replace it immediately as incorrect signals will disrupt gear engagement. Lubricate all moving components with Mopar ATF+4, avoiding overfill which can lead to foaming and premature failure.

When replacing seals, use only OEM-spec Viton seals–generic alternatives harden and fail under extreme temperatures. The chain drive should be tensioned by rotating the adjustment mechanism clockwise until resistance is felt, then backing off ½ turn. Failure to properly set tension results in chain slap and accelerated wear on the sprocket teeth.

Inspect the transfer assembly housing for cracks, particularly around mounting points. If corrosion is present, clean the area and apply a zinc-rich primer before repainting. The rear output flange should spin freely without noise; any grinding indicates bearing failure requiring full disassembly.

Understanding Your 4WD Power Distribution Assembly Layout

For precise component identification, reference the central housing’s numbered callouts–section 3-7 covers the planetary gearset (ring gear, sun gear, carrier), while 8-12 detail the shift collar and fork mechanisms. Label positions follow clockwise progression starting at the 12 o’clock position (input shaft) with tolerance specs of ±0.05mm for mating surfaces. Use a torque sequence chart for reassembly: begin with the rear output flange (85 Nm), then the mode selector (45 Nm), progressing to the front differential coupling (60 Nm) to prevent warping.

Critical wear points include thrust washers (item 19, thickness 2.1mm ±0.02mm) and the synchronizer sleeve (item 23). Replace these if groove depth exceeds 0.3mm or if engagement teeth show chamfer damage beyond 15%. For fluid service, drain the assembly within 10 minutes of operation (viscosity ≤ 15,000 cP) using the fill plug at 6 o’clock–never mix ATF with 80W-90 GL-5 lubricants. Verify proper operation by checking shift detent resistance (12-18 N) and output shaft endplay (0.07-0.15mm) before road testing.

Key Mechanical Elements in the NP246 Powertrain Splitter

Start inspections by locating the input gear, typically positioned at the front of the housing. This 24-tooth helical gear meshes directly with the transmission output shaft and transfers torque to the intermediate shaft. Verify its alignment using a dial indicator–runout should not exceed 0.05 mm, or premature wear on the bearing races will occur. Replace the gear if visual inspection reveals pitting deeper than 0.2 mm or if the splines show signs of fretting corrosion.

The mode fork and slider determine torque distribution ratios. The slider, a hardened steel ring with internal splines, engages the front or rear output shafts via the fork’s actuation. Apply molybdenum disulfide grease sparingly to the fork pivots–excess attracts abrasive contaminants. If the slider binds during engagement, check the fork’s pivot pins for deformation; pins bent beyond 0.1 mm tolerances impair smooth shifts and must be replaced.

Examine the chain drive assembly for elongation. The silent chain connects the drive sprocket (mounted on the intermediate shaft) to the driven sprocket (linked to the rear output shaft). Use a caliper to measure chain stretch; a span exceeding 295.5 mm between 20 links indicates replacement is necessary. Lubricate the chain with gear oil meeting GL-5 specifications–any substitute will accelerate bush wear, leading to skipping under load.

The range selector assembly includes a planetary gearset with a 2.72:1 reduction ratio. Inspect the sun gear teeth for spalling; even minor flaking compromises torque multiplication. The internal ring gear should rotate freely without axial play–use a non-contact tachometer to confirm no drag exceeds 0.3 Nm. If noise persists under deceleration, suspect misalignment of the carrier bearings; shim the case halves to restore proper preload.

Seals and bearings require precise torque values during reassembly. The front output shaft seal (P/N 45038-60010) must be press-fitted to a depth of 8.5 mm using a dedicated installer–failure to do so causes leakage within 5,000 km. Torque the rear bearing retainer bolts to 25 Nm in a crisscross pattern; uneven loading distorts the raceway, creating hotspots detectable with thermal imaging after brief operation.

For electrical components, test the position sensor resistance values. The A/T indicator switch should read 120–160 ohms at 20°C; deviations suggest internal corrosion or worn contacts. The solenoid controlling clutch engagement draws 1.2–1.8 A at 12V–measure current draw during cycling, as excessive values indicate friction plate drag. Replace the solenoid if voltage drops below 11.5V during activation, as insufficient clamping force leads to viscous coupling slippage.

Step-by-Step Breakdown: Servicing the AWD Gearbox Assembly

Begin by securing the unit vertically in a soft-jawed vise, aligning the rear output flange perpendicular to the workbench. Mark mating surfaces with a scribe–not permanent ink–to preserve alignment during reassembly. Remove the 12mm bolts circling the tailhousing first; these fasteners often seize after moisture exposure, so apply penetrating oil 24 hours prior and use a 6-point socket to prevent rounding.

Component	Bolt Size (mm)	Torque Spec (lb-ft)	Removal Tool	Special Note
Tailhousing flange	12	30-36	6-point socket	Apply thread locker on reinstall
Shift motor mount	10	18-22	Flex-head ratchet	Disconnect wiring first
Input gear nut	27 (spanner)	120-140	30mm crowfoot	Lock output shaft

Separate the rear half by tapping gently with a brass drift at the seam–not the bearing races. Store components in sequence on a magnetic tray or labeled compartments to avoid misplacement. The intermediate shaft typically remains in the front housing; if stuck, apply heat (150°C) to the housing bore while cooling the shaft with compressed air to encourage thermal contraction.

Inspect the mode fork grooves for burrs using a fiber optic camera; even minor imperfections cause incomplete engagement. Lubricate new synchronizer sleeves with Molykote BR-2 before installation–standard grease shears under torque. When reinstalling the shift rails, align the detent ball holes with the channel in the housing using a 0.5mm feeler gauge to verify depth before securing the plugs.

Replace the speedometer drive gear if teeth show wear beyond 0.2mm; failure to do so skews readings. Clean the vent tube with 0.5mm wire–clogged vents cause internal pressure buildup leading to seal failure. Apply Loctite 242 to the 8mm dowel pins during reassembly; these locate critical alignment between housing halves and omission risks gear clash.

Torque the input gear nut in three stages: 80 lb-ft initial, 110 lb-ft intermediate, final 125 lb-ft with a 2-foot breaker bar while locking the output flange. Rotate the assembly by hand after each stage to distribute preload; binding indicates incorrect bearing preload adjustment.

After sealing, pressurize the vent port with 15 psi to verify rebuild integrity. Monitor for leaks at mating surfaces for 30 minutes–any weepage mandates disassembly and inspection for damaged gaskets. Store the unit horizontally until installation to prevent lubricant migration from critical bearings.

Maintenance Points for the NP246 All-Wheel Drive Unit: Critical Components

Replace the mode fork bushings (located between the shift rails and housing) every 60,000 miles–earlier if you notice grinding during mode shifts. These nylon inserts wear unevenly and fail without warning, often causing the chain to disengage under load. Check tolerance with a feeler gauge: 0.003–0.006 inches indicates serviceability; anything beyond 0.010 inches demands immediate replacement. Always apply molybdenum disulfide grease to the new bushings before installation to prevent dry starts.

Inspect the drive sprocket bearing cups (press-fit into the rear output shaft bore) during fluid changes. Spin the rear output shaft by hand; resistance or rough rotation suggests brinelling of the 12-point 52 mm tapered roller set. These cups rarely show external leaks but degrade internally, leading to catastrophic chain slippage. Use a micrometer to confirm wear limits: .001 inch deviation from OEM specs means replacement. When reinstalling, heat the housing to 250°F for 10 minutes to ease cup insertion–never force with a hammer.

Less Visible but Equally Critical Wear Zones

The mainshaft seal (front input shaft interface) should be swapped every other fluid service, even if no leaks are visible. Silicone migration into the unit contaminates lubricant within 20,000 miles, reducing friction modifier efficacy. Cut the old seal flush with the housing bore using a razor blade–tapping it out risks damaging the sealing surface. Always coat the new seal lips with NLGI Grade 2 synthetic lithium complex grease and seat it 0.030 inches below the housing face to prevent shaft contact during assembly.

Check the low-range clutch pack (behind the rear output planetary) for glazing–discolored steel plates indicate heat cycles exceeding 400°F. Glazed plates slip under torque, imitating viscous coupling failure. Soak new plates in Dexron VI for 24 hours before assembly to restore static friction; install only OEM friction material–aftermarket plates often disintegrate under 4LO cycling. Torque the snap ring to 45 ft-lbs in three equal increments, rotating the shaft between steps to ensure even preload.