Not on the Dauntless. The factory gears are/were nylon on metal and prone to crumble. I'd be pretty surprised if original gears were still in a running engine 42 years after the last ones left the factory. It's not a terrible job to replace them, just get a service manual and follow directions.
'81 Scrambler w/ FI 360 AMC, 33x12.50 BFG M/T's, 5" of lift, ARB'd Dana 44's F & R, Dana 300 clocked & twin sticked w/4:1, Warn XD9000i, etc...
2002 Grand Cherokee Limited, 2008 Overland Grand Cherokee, a 1976 CJ-7 in pieces and 3 more off-brand 4x4s...............