Dan the Gear Man Tech® Note 1:
Wear on the clutch teeth is the most common reason to replace a NP205 Low Gear. Worn clutch teeth can cause the transfer case to jump out of 4x4 low range under load. Another place to look for wear is inside the shaft bore. 205's run with low or dirty oil will often have low gears that have scored or galled bearing bores.

Dan the Gear Man Tech® Note 2:
Always check your Low Gears for wear in these 4 areas: Bearing Bore (should be smooth with no ridges or pits), Thrust Faces (should be smooth), Clutch Teeth (should have sharp edges) and Gear Teeth (check for burn marks, chips, and broken teeth).

Dan the Gear Man Tech® Note 3:
Optional Matching Parts for TK10859 are:
QU50185 Low Gear Bearing Rollers (use 4 packs of 16 each, 64 total needle roller bearings)
TK10661 or QU50339 Clutch Rings
QU10689 Low Gear Lock Ring
QU50359 Low Gear Bearing Spacer
QU50256 Low Gear Thrust Washer
QU10316 Anti-Rotation Pin
QU50345 32 Spline Front Output Shaft
TK50084 32 Spline Rear Output Shaft

Dan the Gear Man Tech® Note 4:
Need Tech Help on rebuilding your NP205? Get my TM2000 New Process NP205 Transfer Case Service Manual. A Complete NP205 shop Manual with over 375 color photographs is your indispensable NP205 resource for Repair Procedures and Parts Identification. Complete coverage of Disassembly, Inspection, and Reassembly Procedures. Also, Shop Notes, Tool Recommendations, Complete Parts Guide, and full color Exploded Views, including Right Drop and Left Drop Models, plus GM Specific Parts. Covers New Process NP205 Transfer Cases found in Chevrolet, Dodge, Ford, GMC, and International Harvester (IHC) 4x vehicles from 1969-1993.
Or my TM2002 for the Exploded Views and Parts Guide only. Fully Illustrated with dozens of crisp color photographs for EASY Parts Identification! This Manual includes 10 page Parts Identification Guide with full color Exploded Views.