Knocking noise while in gear

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marknor2002

New member
Hello I am new to the forum. I have a 2001 4Runner Sport 2wd. The vehicle has been dealer maintained and have the records from every major service done on the vehicle. It is extensive from timing belt changes to valve rebuild and suspension work. The 4Runner has 306000 miles yes that is correct. The vehicle is as clean as you would find with 120000. Owner was meticulous on maintenance. However the 4Runner too has developed a knocking sound only after the vehicle has warmed to operating temperature. The knocking only occurs when the vehicle is in gear and stops when I take it out of gear. The 4Runner shifts out just fine. I am trying to pinpoint location of knocking. Since there does not seem to be many maint records from previous owner in regards to transmission I am thinking it could be a bad flex plate or torque converter.
 
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marknor2002 said:
Hello I am new to the forum. I have a 2001 4Runner Sport 2wd. The vehicle has been dealer maintained and have the records from every major service done on the vehicle. It is extensive from timing belt changes to valve rebuild and suspension work. The 4Runner has 306000 miles yes that is correct. The vehicle is as clean as you would find with 120000. Owner was meticulous on maintenance. However the 4Runner too has developed a knocking sound only after the vehicle has warmed to operating temperature. The knocking only occurs when the vehicle is in gear and stops when I take it out of gear. The 4Runner shifts out just fine. I am trying to pinpoint location of knocking. Since there does not seem to be many maint records from previous owner in regards to transmission I am thinking it could be a bad flex plate or torque converter.
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Just a shot in the dark, but maybe the exhaust is hitting something when in gear? Maybe a worn mount which is causing it to shake more than usual?
 
When you say knocking, where is the location of the sound? Knocking as in a valve knock? Or more like a loose part sort of knock? Does it increase along with RPM's?
 
Have not pinpointed yet where the knock is coming from. I took it to my mechanic yesterday afternoon and we worked on it till late that evening. He used a stethescope to see where the knock was coming from. But could not clearly hear where it was coming from. So we tool the dust cover off the transmission and inspected the face plate and made sure the bolts where snug on the torque converter. The flex plate did not appear to have any stress cracks and bolts where tight. So we decided to look at the pullys and one of the tensioner pullys on the ac unit the bearing were very bad and the pully was loose so we took the power steeing and ac belts off and put the truck in gear and there was no knocking what so ever. So I purchased a new tensioner pully and we installed that and the belts and started it back up in gear and let it run and there was no knocking. So we thought that might have been the problem. But when put it in reverse and pulled out of the bay of his garage you could here the knock once again and when i put it in drive you could here it Drove home and to work this morning and still here the knock. Escpecially when I come to a stop light you here it more...not so much when driving or reving the engine. So I am to go back to his garage and he though we should check the oil pump as this 4Runner has over 300000 miles and it never has been changed. Will also check oil compression as well. He also though the crankshaft bearings might be bad. Not sure though he said...so one thing at a time at this point until we figure it out. The knock seems to get louder once the engine is warm or at operating temp. and when the car is in gear and under a load. If that makes sense.
 
Also just wanted to ask and see what others thoughts were on this. The transmission fluid is somewhat brownish and I am not sure when the previous owner had serviced the transmission. My question is can broken down dirty trans mission fluid cause knocking while in gear? The 4Runner shifts out fine from gear to gear...no real hard shifts what so ever. just thought i would ask.
 
Just an Update. Last week timing belt, water pump, idler pulley, tensioner, Tstat, oil pump, crank shaft checked since we dropped oil pan (Mechanic check all tolerances and they were in range) and crank looked very clean no oil sludge, all drive belts replaced and also replaced outside and inside pulley and bracket as the older pulley looked warped. All that done and it is running really good. Though the thumping sound ...though not as loud is still there after the 4runner warms up. But the sound is better which i am thankful for.
 
None of that stuff should make a knocking noise only when in gear. If I had to bet, it would be the flex plate. In gear, makes sense, you won't be able to see the cracks until the trans is out. It cracks around the bolts that hold it to the crank.
 
Had taken the flex plate dust cover off and we checked all the bolts. turned the crank so that we could see if there was any cracks it did not show any. But like you I am leaning towards the flex plate.
 
marknor2002 said:
Hello I am new to the forum. I have a 2001 4Runner Sport 2wd. The vehicle has been dealer maintained and have the records from every major service done on the vehicle. It is extensive from timing belt changes to valve rebuild and suspension work. The 4Runner has 306000 miles yes that is correct. The vehicle is as clean as you would find with 120000. Owner was meticulous on maintenance. However the 4Runner too has developed a knocking sound only after the vehicle has warmed to operating temperature. The knocking only occurs when the vehicle is in gear and stops when I take it out of gear. The 4Runner shifts out just fine. I am trying to pinpoint location of knocking. Since there does not seem to be many maint records from previous owner in regards to transmission I am thinking it could be a bad flex plate or torque converter.
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Hi Did you ever managed to find out the problem? I am having same issues.....
 
If its a slow 'thump, thump, thump' sound that increases/decreases with rpms at around idle while in gear, i think they all make it after a while. As long as we're not talking rod noise, really loud hammer like sounds heard down the street then I think it's all good, mine does it too. Luck.

Edit: Oh yeah as OPs said it's only heard with a warmed up engine, in gear, idling and then slight changes occur as some fuel is applied and while sitting inside, windows up, can't be heard from engine bay or outside vehicle. Once you drive off say above 5-8mph it can't be heard, only under light throttle from idle in gear. Its not loud, most riders never hear it, only us attuned 4runner freaks, haha.

My hunch is something has worn over time causing an odd oscillation tied to engine rotations, the thumps are about 2-4 per second, so not exactly matching any movement of engine or trans other than general rpms. It'll either last that way forever or turn more serious as something wears further.

I've checked with steth all over, checked flex plate, ect, ect.
 
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I had thumping/knock while in gear and stopped or just truck moving slow at idle.

Took me 2 weeks to find it and it got louder as time went on. Sounded like engine compartment from inside truck.

The flange on rear tail pipe flange just after muffler rusted off. The knock was the exhaust system moving around and as the flange started to fail more and getting loose and more movement and louder thumping/knock until it came apart and it stopped, but then I could hear the separated pipe rattling on cross member. That's how I found it. Put new muffler and tail pipe on and no thumping/knock sound.
 
Hopefully someone can help me with this same problem. I did replace the flex plate about three weeks or so ago since it was making a really loud knocking sound. Took it in to my mechanic and long story short, it was my flex plate that was making that sound and it was due to the flex plate being cracked.

Fast forward about a week after my mechanic replaced the cracked flex plate and the knocking (more like a pinging noise) came back again. Brought it back to my mechanic about a week or so ago and after having it for about a day, he advised that it was a bolt that was too long that was hitting my engine and he had to file down the bolt. Again everything was honky dory and no sounds coming from under my vehicle.

Fast forward to Tuesday of last week, the sounds came back after driving it for 2-3 days. Again it's more like a pinging noise, and still coming from underneath my car and from where it sounds like it's coming from, it's around where the transmission and engine connects. I haven't had time to bring it back to my mechanic but maybe you folks can help me out first so I could maybe help my mechanic know where to look or what to look for.

Thanks.
 
drei4runner29 said:
Hopefully someone can help me with this same problem. I did replace the flex plate about three weeks or so ago since it was making a really loud knocking sound. Took it in to my mechanic and long story short, it was my flex plate that was making that sound and it was due to the flex plate being cracked.



Fast forward about a week after my mechanic replaced the cracked flex plate and the knocking (more like a pinging noise) came back again. Brought it back to my mechanic about a week or so ago and after having it for about a day, he advised that it was a bolt that was too long that was hitting my engine and he had to file down the bolt. Again everything was honky dory and no sounds coming from under my vehicle.



Fast forward to Tuesday of last week, the sounds came back after driving it for 2-3 days. Again it's more like a pinging noise, and still coming from underneath my car and from where it sounds like it's coming from, it's around where the transmission and engine connects. I haven't had time to bring it back to my mechanic but maybe you folks can help me out first so I could maybe help my mechanic know where to look or what to look for.



Thanks.
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Might be best to post a video or sound file of your sound. This may help narrow it down

Sent from my SM-J337V using Tapatalk
 
Did your mechanic put loctite on the flex plate bolts (both the inner 8 bolts and the 6 bolts that hold it to the torque converter)? Did he torque them to spec? It's possible that some of the bolts are backing out.

If all of the correct bolts were used when he replaced the flex plate, none of them should have been too long. It's a little confusing too because no bolts should ever be able to hit the engine (again, the 8 inner flex plate bolts go into the crank shaft and the 6 bolts go the opposite direction into the torque converter).

Hope this helps
 
x2 on a bolt backing out.
I had the same basic issue, but not with my flextplate/torque converter.

I replaced my catalytic converter, and a few months later got a bad knocking/rattling noise when in gear, but especially noticeable when in reverse.
Turns out the bolts that anchor the cat mount to the frame had backed out a bit and the mount was rattling something fierce. The slight angle change when in different gears must have set off the rattling, vs when in park.
 
Following this thread, sometimes i feel like i hear the same thing coming from my 01 but I mainly notice it when the ac is on and sometimes goes away after turning it off
 
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