Crunching noise back side of engine

[Fishman2009]

Ok, I JUST changed the the u-joints on my aplha one gen II drive. and the thumping noise I got turning left or right was gone But , I heard a diff noise that now seems to have gotten worst. It a metalic noise that I hear when i stock my head down in the back side of the 4.3 eng while idling. intermitten crunching sound. i do not hear this fromt he drive it self , that is quiet. seem no diff if I turn or not and at idle that is with no forward or reverse gear. just idleing with muffs. on the water if i ramp the rpms in netural it will shrill nosie at a band of rpms and go away and shrill as you drop them and go away when it hits lowest. I'm praying its not the engine and hopefully the gimbal bearing gone since it had changed the ujoints. but havign never heard a bad gimbal not sure is its that or somethign else. then soemwhere on here some one mentioned a engine coupler. im really lost. so askign thoses that ahve hear bad gimbals and all to speak up.. i got a week before this was going up on a weeks vacation and of course money is tight and if i can do it I will. just need some input where to start. Dealer did check gimbal when I had the orginal progblem and said he saw nothign wrong with either gimbal or u-joints , but i changed them due to the noise was gettign worst there and the info i read here and that is gone. just this crunching at idle and shrill 1200 -1800 i would say rpms.

 

[Fishman2009]

Re: Crunching noise back side of engine

let clarifiy that, i did not change the gimbal , just the ujoints.

 

[Snowfish]

Re: Crunching noise back side of engine

Sounds exactly like the gimbal to me. If the dealer missed the bad u-joints, they probably didn't check the gimbal that close either. My gimbal was a constant growling noise. Then that shrill sound when you rev it. The cost of buying the right puller was about the same to having the gimbal done at a shop. So this time, I opted to bring it in.

 

[Fishman2009]

Re: Crunching noise back side of engine

OK , what diff a day makes.. Pulled the drive and check bearing, seems fine, so had the wife hold the hose in the water inlet on the back with drive missing. (she got wet, go figure) I figure if noise gone then in the bearing or elsewhere. But it was still there. and guess what , its appears to be becoming from the exhaust bellows. I used a sounding stick and all is quiet till I hit the bellows, the exhaust manifolds are both cool, then both have rubber boot connector to a 90 degree bend part that again has rubber boots to connect to yet more below. there lays the diff. the one 90 degree is cool as it runs, the other is warm to very very warm and the same goes down the tube to it disappears under the output area and into the transome.. so whats does anyone think this might be? engine purrs and does not lack power, is there a diagram of the water ports on the exhaust, maybe one side is plugged and the hot gases are causing a reactrion and the noise??? when I put the sounding stick one the exhaust manifolds or on the engine no noise, only on the exhaust after the first boot. And the noise sound seems to be orginating down below where the 2 meet, Help, vacation a week away

 

[Fishman2009]

Re: Crunching noise back side of engine

I figured it out with help online from diff part suppliers info.. seems there are things called exhaust shutters inside there that can go bad.

 

[Gary H NC]

Re: Crunching noise back side of engine

The exhaust flapper is down in the Y pipe.

 

[Bondo]

Re: Crunching noise back side of engine

Ayuh,... Seperate the exhaust at the Top of the Y-pipe,...
That's where you Should find the shutters...
If Not,... It's been run without Water,...
Now, they're burnt up,+ fallen down the pipe...