Engine sound change in the DD

[WHATROAD]

Okay, maybe it's just too many years of listening to loud engine output. Maybe I suddenly lost a range of hearing that I use to have. Maybe not! We finally had a cold snap and the heater is on full in the soft top of choice. This morning, on the way to work at 6, I thought the jeep sounded muffled. As if the muffler had become better. I know, right!? Didn't think about it and trudged into work. Bound for home and again the engine sounds are muted. it just doesn't have the jeep AMC 258 i6 / 4.2l CID sound I know so well. No vacuum hiss, no loud compression on down shift, no water leaking from the water pump, no changes in power that I can tell, Weird! Beat down tired and not needing to drive tomorrow I'm just not ready to tear into it for a solution I'm baffled to come up with. Also not hoping to find that something of major bad has crept into my life. Hoping on hearing loss I'll take all the input on this you folks want to give. Water Pump? Thanks in advance!

 

[Torxhead]

Well for starters, I hope that you do not have the original muffler and cat.

 

[WHATROAD]

Hahahaha, nah, 33 years later some things have met their life limit. It's just weird. I was too tired to run it through my head so I popped a top and let it be for awhile. It's almost like I've lost compression and with it the usual volume of sound but I have not lost any performance as I can tell. When I down shift, I don't get the usual increase in sound that I am use to. I can feel the compression brake happening but the sound is muted. Can the cat have failed in such a way as to restrict the flow and decrease the output? This is a new one on me.

 

[WHATROAD]

There don't seem to be any of the usual cat failure symptoms. No bad smell, no rattling, no power loss, and I don't have a check engine light so that isn't an indication either. I'll take it for a long drive in the morning, maybe the cat is just fouled with carbon or something and needs a blow out. I'll let you all know what this comes out to be. Happy Thanksgiving everyone!

 

[WHATROAD]

In my quest to come up with the answer for a suddenly quieter jeep I was led to the repair of two new problems. I was able to detect a fan clutch noise that was accompanied by a leaking water pump. Replaced both. Now the decibel level is even more reduced. Still no logical answer but Mrs. WHATROAD is impressed. Haven't told her yet that I had nothing to do with it. I am certain nothing good can be following. Weirdest thing this AMC has ever done to me. Whole exhaust was welded two and a half years ago. Leaning towards the Cat as being the culprit. We'll see.