Over time, all internal engine wear surfaces become worn.
This is true for crankshaft journals, connecting rods, camshaft lobes, piston rings, bearings, etc.
When rebuilding a worn engine, you'll need to replace them all to regain the engine's original performance.
This replacement main bearing set fits 72-83 CJ5, 72-75 CJ6, 76-86 CJ7, 81-86 CJ8 Scrambler, 72-73 Commando, 72-73 Trucks, 72-83 Cherokee / Wagoneer, 73-74 DJ5, 84-86 Grand Wagoneer, 87-90 Comanche MJ, and 87-90 Wrangler YJ models equipped with 3.8, 4.0, and 4.2 liter engines with 0.030-inch under size crank.
Replaces OE 4289M.030.
