Around 92, 000 or so i noticed when in overdrive around 35-40 mph 1400-1500 revs while applying light throttle to maintain my speed there is a growling from the front also when in parked and you rev it up to that rpm range you can hear it . Yet i drop it in third take the revs up to 1600-1700 nothing. Also during heavy highway merging theres nothing and any other speed nothing. I have checked/replaced the idler, tensoner, belt while the belt was off i checked the pullies for wear and or play. I also checked the whole driveline/ frontend all within spec . Anybody had this problem ??

 

Forgot to add that its a 2006 4.3

 

I use to have this problem too, Then i swapped a 5.3 in and all my problems were gone

 

6.0 and t56 out of buddies wrecked gto is getting a turbo and next winter hopefully be in but till than i am daily driving this . I am half asleep so i think i posted this in the wrong section . I thought the one above was for preformance only opps . I figure i will be flagged now .

 

Catalytic converter coming apart?