Wanted to see if it was a good idea to put a shift kit on a 99 4x4 durango with 155,000 miles on it just wondering.

If you kept up with maintaining the trans I would say yes. Either way it helps your trans. 155K is a lot of mileage.

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1998 Durango, 5.9L Built Motor Bored 20 Over, P&P Heads, K&N Ram Air CAI, MSD Ignition, 52MM Fastman TB, Built T-Case, Custom Built Trans, Air Bags, Magna Flow 3" Cat Back Exhaust
On and On!