Major UGH - engine knock

[n2audio]

Major UGH - engine knock (Update - might be transmission)

This post can be deleted -- reposted as transmission noise.


So I bought this high mileage aviator about a year and a half ago with 137k on it. It had a new transmission which was a MAJOR plus for me.

It now has about 162k on it and has run great in general.

Today I was going through a toll booth which means moving slowly along a concrete barrier -- when I began to accelerate, clack clack clack clack clack...
It sounds like it's definitely from down low.
I immediately feared the worst, but I was just beginning a 100+ mile round trip with passengers and wasn't able to explore until getting home.
There's no noise at idle. It seems most pronounced at low speed and light throttle. I don't sense any problems on the highway.
I did hear the noise a few times during the trip - at lower speeds whenever I drove by something that reflected the noise.

When I got home I checked the oil. It was about a qt down -- I changed it recently, I think I just failed to bring it up to the appropriate level when I refilled it. Oil's very clean.
I tried to duplicate the noise in park and couldn't -- at least not up to 3k rpm or so. I crept underneath at idle and didn't hear anything strange. I heard a "whirring" from the oil pan, but it didn't sound out of place.

I've done virtually all my own maintenance on 6 different vehicles spanning well over 10 yrs and about 500k, and a few fairly major jobs, but NEVER had a bottom end problem - to diagnose or attempt to repair.

 

[Nomad8326]

Fill the oil to proper level and check for noise again.

Engines IMO tend to be picky about how much oil is in there and can cause all sorts of noise.

Hopefully that's all yours is.

 

[n2audio]

I adjusted the oil level and drove it again quite a bit yesterday.
It seems to knock very little (or at least much quieter) when it's cold, but once it warms up it's there during light to moderate acceleration. I can't hear it on the hwy but I'm guessing it's still there.
I'm going on the assumption that there's something wearing out in the bottom end and starting to research my options for engine replacement.

 

[n2audio]

I got underneath today and gave it a much better listen.
The noise does not SOUND like it's coming from the engine. It sounds like it's coming from above the transmission.
I recorded some sound -- ever heard anything like this?

https://www.youtube.com/watch?v=vJ_ozfL4LIY

 

[D Hook]

Not sure what it is but it's not a knock like a failed bearing. Hopefully someone will chime in.

Good luck and keep us posted what you find.

 

[FordExplorerFan3]

Overfill the oil sometimes it will quite the noise because it will take more pressure to buildup

 

[joeyd0730]

I had a similar noise, but it was only heard at idle.. it turned out to be the torque converter.. there was no noise under load, only at idle..

 

[n2audio]

Had it checked out today. I was surprised when the tech traced it to the driver's side catalytic converter. There were two tech's listening with a stethoscope and I stood under it as well.
I was happy to hear that, although having it replaced won't be any less than $1k -- I spoke with the diagnostics shop and another exhaust specific shop. They both said it's the whole system or nothing. The system is sold complete (in 3 pieces) and universal cats won't cut it.

Although I found a company through RockAuto ( Davico ??) that sells the 3 pieces individually and I can buy the driver's side for $200+ shipping. It bolts to the manifold, clamps to the passenger's side pipe, and bolts to the downstream portion of the system. Seems doable to me.
So I will without a doubt be exploring that option.