Truck ran fine for week.changed oil started knocking.i went to listen pulled plug wires one at time,no difference.still good oil psi. doesnt sound like anything(knock) ive heard son revs truck knock seems to come and go almost go away!i research 4.3 found several issues with balance shaft.found TSB gm repair bulletin tensioner kit to install on 96-03 4.3.i cross ref every gm pt number found aftermarket kit available.jump gun didnt further diagnose engine my bad as im fairly good wrench.tore front of engine down,t-chain very worn.could cause balance shaft noise/knock?pull engine up to get oil pan off btw the oil was black sludge(fresh oil only a day ran)and oil filter was seized?took 3 hours to get off.no rods loose on crank little side to side.i installed tensioner kit the chain was single roller per gm cross ref 12458911. but looked chincy. any ideas on the knock in case we start up and its still there?we put in hv oil pump in case guage was wrong and check rockers too. Checked flex plated and torqued conv bolts, h balancer everything external i could think of.pushed down on rocker for collapsed lifters,no bent p rods,took long pry bar couldn't find play in pistons.all be it they were hard to get to the engine was still in truck.
My car has 190000 miles.
My car has an automatic transmission.
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