Help Diagnosing Knocking Noise

Joined
May 7, 2007
Messages
184
Location
Minneapolis MN
Hopefully not rod knock. But I’m an amateur, I’m open to opinions. Here’s the strange thing. This knock seems to happen only when turning to the right. The knock frequency is directly linked to engine speed.

I can’t replicate the sound at idle or when the rig is NOT in motion. Only when I’m driving and mostly when turning right.

1972 FJ40 1F engine with SM420 transmission.

From the driver’s seat, the sound seems to come from the left side.

Three videos
1 - Recently started, mostly warmed up on a summer day - Sounds good to me.
Just started
2 - Driving, with knock sound on right turns - Knock gets obvious at about 22 seconds.
Driving
3 - Back in the garage. No knock, fully warmed up. Sounds like normal in the garage.
After drive

Any help or advice would be greatly appreciated!!! It’s tough to track down the source when it only happens in motion.
 
Last edited:

whitey45

SILVER Star
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Oct 17, 2007
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5,092
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San Gregorio
Definitely not a rod knock, so thats good news!
Check your hubs, lug nuts, steering, tie rods, anything with play. Seems to only do it in right hand turns? Transfercase linkage rattle?
 
Joined
May 7, 2007
Messages
184
Location
Minneapolis MN
The thing is though that the knock definitely has the same frequency as the engine RPM. So not likely anything at the hub.
 
Joined
Jan 19, 2021
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47
Location
Renton, WA
Engine sounds fine. I don’t think that has anything to do with the noise you are hearing. Sounds like it happens a little on left hand turns too. 42 seconds on drive video. To me, this sounds like creaking and popping. I agree with whitey45, check suspension, steering linkage, front brakes, hub, etc. put the vehicle in the air, turn the front to a full right turn, spin the tire, shake things, just generally look everything over. I really don’t think this is engine related. Good luck, let us know what you find.
 

whitey45

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5,092
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San Gregorio
First off, it sounds nothing like an engine knock( 35 year mechanic) and an engine knock doesn't go away, once a rod bearing is comprised it only gets worse, real quick. It very much sounds like the fan is rubbing the shroud? Check all your clearances everywhere. A broken engine mount will cause fan interference under certain conditions. You cant rule out anything at this point, and it can be a hundred different things.
 
Joined
May 7, 2007
Messages
184
Location
Minneapolis MN
I need to swap out my radiator. The new unit arrived today. Maybe I’ll remove the fan shroud temporarily as a test.
 

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