Q: 3rd gear catches when up and down shifting. on 1992 Jeep Wrangler

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I believe the synchro needs to be replaced. Whats the average cost of that?
(1) Answer
This is essentially removal of the transmission, disassemble and replace components as overhaul.

Figure labor is about 10 hours (around $1,000). Parts - as needed - figure maybe $250 - 350.

You may be able to get an inexpensive assembly to just "drop in" - worth looking into as well.