Uh-oh! Ominous knocking sound from front end - advice? (1 Viewer)

[buddysharp]

Guys, freaking out here and could use some help. So, wife has noted a "knocking sound" intermittently over last year or so but I'd never heard it. Truck has 134K and been babied. Rolled up to a stop light and heard a noise from the front end like someone had a hammer inside the driveline. Not a rod knock. took it out of gear and noise stopped. put it back in and re statred and then mysteriously disappeared. Clearly from the engine bay, more on passenger side. No warning, easy driving, couldn't really feel any vibration but man was it loud.

 

[Trunk Monkey]

Noise in rhythm with motor or with movement? Check CV's, specifically the end c-clip behind the dust cap.

 

[buddysharp]

In rythym with motor but not moving - high speed knock but - picture yourself hitting a piece of metal with a hammer about as fast as you can. Only happens when stopping and begins at stop of forward motion. If I take it out of gear it stops. And it is completely random.

 

[buddysharp]

Hey Trunk Monkey, thanks. RU suggesting the clip is broken and flapping?

 

[Trunk Monkey]

Some folks have had the c-clip retaining the CV slip off the end allowing the CV to rotate in the knuckle. You wouldn't get any motion if this was the case as the open diffs would send all the power to that wheel. So the knock doesn't change with RPMs?

 

[2001LC]

If I understand you correctly it is when stopped in gear brake on, that you get most sound?

If ^that the case; The "D" Vibration as it's called manifest itself from different point. The two most noteworthy up front are engine cover & roof rack.

Next time you hear it: open sun roof, reach up and grab the roof rack cross bar. Or put on E brake and check under hood placing hand on engine cover.

 

[paflytyer]

If I understand you correctly it is when stopped in gear brake on, that you get most sound?

If ^that the case; The "D" Vibration as it's called manifest itself from different point. The two most noteworthy up front are engine cover & roof rack.

Next time you hear it: open sun roof, reach up and grab the roof rack cross bar. Or put on E brake and check under hood placing hand on engine cover.

You're not suggesting to leave the truck in gear with e brake on, and open hood, are you? To the OP, please don't do that.

If the sound stops after you stop, check for something hitting the fan as the weight shifts forward when you come to a stop. The fan hitting the shroud will make a sound like you describe as well.

 

[buddysharp]

Guys, thanks. Picture small guy with ball peen hammer inside the engine bay. This is not a vibration, this sounds like metal spanking metal. Brake on, in gear. constant fast knocking. Couldn't really vary with RPM as we were stopped with brake on. Take out of gear, knocking gone. put back in gear, knock returns. roll forward, knock disappears and can't be reproduced until the knock decides it wants to return.

 

[buddysharp]

i got it on video on my smart phone but the file is huge and I can't upload it. Working on that now.

 

[paflytyer]

Guys, thanks. Picture small guy with ball peen hammer inside the engine bay. This is not a vibration, this sounds like metal spanking metal. Brake on, in gear. constant fast knocking. Couldn't really vary with RPM as we were stopped with brake on. Take out of gear, knocking gone. put back in gear, knock returns. roll forward, knock disappears and can't be reproduced until the knock decides it wants to return.

If you roll forward in gear and apply brake again will knock return every time? A safe option is to open the hood while someone else is in the drivers seat, in gear, foot on brake with you standing along side looking for noise.

You can kind of hear the fan hitting the shroud in this clip. Just barely touching. Hard to decipher over Jonathan's squeaky brakes.
http://m.youtube.com/watch?v=VTPhidIImF0&feature=c4-feed-u
(Couldn't embed video from iPad)

 

[AimCOtaco]

I think paflytyer may be on to something with the loaded drive train shifting and causing interference. If it is though, I would expect the contact to occur under other conditions as well, like over bumps, etc.

Here's a WAG from left field; Could the Park pawl in the transmission be partially engaging? That's what I hear in my head with the metal on metal, hard and fast description of the sound.

 

[buddysharp]

I thought about where have I heard noises like this. Trying to shift into park when rolling - similar but this sounds different.

It doesn't recur with any regularity. It only occurs when sitting at idle in gear. Fan hitting metal is a maybe but this sounded more like internal to drivetrain.

GOT the video uploaded on to YouTube - WILL TAKE A FEW MORE MINUTES TO UPLOAD. Forgive my genius comments and shushing my kids: http://youtu.be/JJ2MNTwqSMM

Files is uploaded! take a listen.

 

[2001LC]

You're not suggesting to leave the truck in gear with e brake on, and open hood, are you? To the OP, please don't do that.

If the sound stops after you stop, check for something hitting the fan as the weight shifts forward when you come to a stop. The fan hitting the shroud will make a sound like you describe as well.

Yes I'm am suggesting use E brake letting off foot brake, this will test brake pump for sound as well. OP needs to get out and work around, under hood and under the vehicle. Should check engine & transmission mounts and fan as-well. You could be onto something with the fan, but until he get out he'll not be able to tell much. A mechanics stethoscope is a very useful tool in this situation

I should have noted to test park brake first, chock wheels and not get in path of vehicle while wife sit in driver seat, but I'm sure he can figure that for himself..

 

[buddysharp]

2001LC, to test like this would mean I could replicate the noise. TOTALLY intermittent. Last occurrence in traffic at stoplight. Rolled to stop, sat for a moment, noise started. NOT a small noise. BALL PEEN hammer on metal. It's a knock not a tap. gotta be either engine (god forbid temporary loss in oil pressure?) or a spinning driveline component.

Going outside to check motormounts and inspect fan shroud for wear. Also crawled up under but nothing obvious on CV boots. Gotta get dust cover off in garage tonight.

Listen to video if you can

 

[LX101North]

Guys, freaking out here and could use some help. So, wife has noted a "knocking sound" intermittently over last year or so but I'd never heard it. Truck has 134K and been babied. Rolled up to a stop light and heard a noise from the front end like someone had a hammer inside the driveline. Not a rod knock. took it out of gear and noise stopped. put it back in and re statred and then mysteriously disappeared. Clearly from the engine bay, more on passenger side. No warning, easy driving, couldn't really feel any vibration but man was it loud.

Hey buddy sharp! This link is a problem posted from pursuit back in '12. He has an 80 series, but the problem sounds identical. Hopefully it's this and not anything too damn expensive. Although expensive and land cruiser go hand in hand. She's a high maintenance BH!
https://forum.ih8mud.com/80-series-tech/549258-help-diagnosing-periodic-knocking-driveline-jacking-while-stopped-gear.html

 

[Sandroad]

It sounds like maybe an exhaust leak (at least it does on my iPad speakers). Could be a cracked passenger side header that sometimes opens up only at low RPM under load?

 

[buddysharp]

Thanks, LX101North, I'm trying to diagnose the mounts. Seems logical but the randomness is not. Still trying to diagnose.

Nope, intermittent sound. once every couple of months; sorry I thought the utube vid would be more obvious.

Gonna go lay on the cold garage floor and try to find something obvious.

 

[2001LC]

I heard it, have you ever check and or flushed your power steering pump fluid?

 

[APKhaos]

Can understandf why you are freaking out. That's a scary sound, and definitely engine related.
Could be motor mounts. Easy to check - just take a look. If the engine can move around a bit under braking there are plenty of opportunities for noise like that.

 

[paflytyer]

Yes I'm am suggesting use E brake letting off foot brake, this will test brake pump for sound as well. OP needs to get out and work around, under hood and under the vehicle. Should check engine & transmission mounts and fan as-well. You could be onto something with the fan, but until he get out he'll not be able to tell much. A mechanics stethoscope is a very useful tool in this situation

I should have noted to test park brake first, chock wheels and not get in path of vehicle while wife sit in driver seat, but I'm sure he can figure that for himself..

I wouldn't always assume. You're telling someone to put their vehicle in drive, engage E brake and get out and open the hood. Not safe. You post 10 pages on stuff detailing every teeny tiny thing and then say you just expect people to figure it out for themselves.

buddysharp, that doesn't sound like the fan hitting the shroud to me. 2001LC is partially correct, if you can get stopped somewhere that the sound is occurring and you have someone else driving, then pop the hood and move around to the side and have a look. Gonna be hard to do in the dark, even with a decent light. Doesn't sound like anything CV related either.

First thing I would check is to make sure you have fluid in the Tcase. Maybe an exhaust shield hitting something, driveshaft tilting and hitting something?...... or I'm gonna guess a broken flex plate . That will make a sound like an engine knock.