Knocking under load.....Advice
Discussion
Just went out for a blast. I started to hear a knocking/tapping whilst overtaking when I pressed the accelerator.
Changed down knocking got worse so I stopped. First gear selected, pulled off the tapping started off and seemed to be intime with the tyre revolutions and gradually sped up.
Stopped the car totally, took the car out of gear and revved it. Sounded perfectly normal to tapping or anything.
Put the car in first and pulled off it started knocking, second still knocking, third the same, put it in fourth and it goes totally and the car drives normally.
Stopped and reversed and still had knocking intime with the wheels.
All this only when the accelerator is applied.
Gearbox up the creak or what?
MikeB
Changed down knocking got worse so I stopped. First gear selected, pulled off the tapping started off and seemed to be intime with the tyre revolutions and gradually sped up.
Stopped the car totally, took the car out of gear and revved it. Sounded perfectly normal to tapping or anything.
Put the car in first and pulled off it started knocking, second still knocking, third the same, put it in fourth and it goes totally and the car drives normally.
Stopped and reversed and still had knocking intime with the wheels.
All this only when the accelerator is applied.
Gearbox up the creak or what?
MikeB
On another inspection the noise is deffo coming from the front, mid section, sounds low down.
It ain't no little tapping either. It's a heavy enough tapping sound to causes quite a clonk when it happens easily loud enough to hear over the noise of the car.
Take the car out of gear when your going and give it a rev and it dissapears. When you put it in say third then it only comes when you apply a little throttle.
Oddly though when the car is in Fourth it completely goes?!
After starting the car now from cold and let it run for a while there is some tapping from the engine, rev it and it is evident but nowhere near as loud or as bad as when the car is going and in gear (except fourth).
Ian mail me over your phone number as I need to pick your brains on this.
mike@pixeltechnology.co.uk
MikeyB
It ain't no little tapping either. It's a heavy enough tapping sound to causes quite a clonk when it happens easily loud enough to hear over the noise of the car.
Take the car out of gear when your going and give it a rev and it dissapears. When you put it in say third then it only comes when you apply a little throttle.
Oddly though when the car is in Fourth it completely goes?!
After starting the car now from cold and let it run for a while there is some tapping from the engine, rev it and it is evident but nowhere near as loud or as bad as when the car is going and in gear (except fourth).
Ian mail me over your phone number as I need to pick your brains on this.
mike@pixeltechnology.co.uk
MikeyB
If the sound goes in fourth yet you have the same amount of accel applied and the same revs... then it cant be a main bearing knock... from what you have described I think you need to look around the gearbox area.
Have you tried holding the gear lever to feel any knocking in the gears?
Have you tried holding the gear lever to feel any knocking in the gears?
Edited by anonymous-user on Saturday 17th June 19:14
Could be brake related - I experienced something similar a year ago.
If it is a big end rattle you will notice it in time with engine speed. See if you still get the rattle when the car is in motion but not under load. Try switching off - but remember you will lose braking power and steering assistance. Alternatively freewheel at nominal revs.
Big end rattle can ease off when you achieve speed and then increase with the load applied. But from your description so far it would appear not to be bearing related.
If it is a big end rattle you will notice it in time with engine speed. See if you still get the rattle when the car is in motion but not under load. Try switching off - but remember you will lose braking power and steering assistance. Alternatively freewheel at nominal revs.
Big end rattle can ease off when you achieve speed and then increase with the load applied. But from your description so far it would appear not to be bearing related.
Edited by firefox1712 on Wednesday 21st June 08:04
UJ's can make a row when they go. They're in time with the rotation of the wheels. When they went on the 350 I only had the noise with power in the lower gears. Get the car up on stands and give the rears a real good shake top to bottom, when I say shake, shake them enough to try and moove the car off the axle stands and get some one to look at the joints when your shaking them.
A useful test I've used (involving a trusted mate!) is to roll one side of the car up onto a kerb. Then lie underneath the rear while mate engages first gear and bounces the clutch around its biting point. Any play, clonking etc in UJs or drivetrain mountings can soon be seen/heard/fle depending on how bad...
When we tried it on my mate's '75 Elite (suspected UJ clonking), he found that the diff had ripped its mountings out of the chassis...
When we tried it on my mate's '75 Elite (suspected UJ clonking), he found that the diff had ripped its mountings out of the chassis...
wedg1e said:
A useful test I've used (involving a trusted mate!) is to roll one side of the car up onto a kerb. Then lie underneath the rear while mate engages first gear and bounces the clutch around its biting point. Any play, clonking etc in UJs or drivetrain mountings can soon be seen/heard/fle depending on how bad...
When we tried it on my mate's '75 Elite (suspected UJ clonking), he found that the diff had ripped its mountings out of the chassis...
When we tried it on my mate's '75 Elite (suspected UJ clonking), he found that the diff had ripped its mountings out of the chassis...
You can do this on a ramp as well
Just use a large chunk of wood at the back so you don't go flying off We tried it on the brake tester but could not get head underneath to see any play
Had another test this afternoon and noticed that it was doing the same sound only when giving it the accelerator pedal. Come off the pedal and the knocking sound dies away.
Going along, take the car out of gear and it dies away. Pressing the accelerator out of gear and the noise is hardly evident.
Put it in fourth gear whilst you are going, give it some accelerator and the noise is not there, power seems normal. Any other gear and the noise is really loud when giving it the accelerator. The knocking also seems to be intime with the wheels.
Got it back home and just let it idle out of gear and noticed that the sound is still there slightly, rev it and it gets slightly louder but not as loud as when in gear and pressing the accelerator when its really loud.
The sound is definately metallic and when in a low gear is really loud, also comes with a slight thud as well which can be felt in the cabin.
Without getting a pipe out and having a good listen around the engine bay the sound soundls like its coming low down from the right hand side of the engine near the back down by the bellhousing.
Anymore thoughts.
Wedg1e thought it might have been an exhaust manifold blowing, anybody had any experiance of this?
MikeB
Going along, take the car out of gear and it dies away. Pressing the accelerator out of gear and the noise is hardly evident.
Put it in fourth gear whilst you are going, give it some accelerator and the noise is not there, power seems normal. Any other gear and the noise is really loud when giving it the accelerator. The knocking also seems to be intime with the wheels.
Got it back home and just let it idle out of gear and noticed that the sound is still there slightly, rev it and it gets slightly louder but not as loud as when in gear and pressing the accelerator when its really loud.
The sound is definately metallic and when in a low gear is really loud, also comes with a slight thud as well which can be felt in the cabin.
Without getting a pipe out and having a good listen around the engine bay the sound soundls like its coming low down from the right hand side of the engine near the back down by the bellhousing.
Anymore thoughts.
Wedg1e thought it might have been an exhaust manifold blowing, anybody had any experiance of this?
MikeB
Edited by mikeb on Sunday 18th June 23:05
Mike, If the sound goes away when in 4th, then it is probably the layshaft cluster in the box, as in 4th the drive will be straight through. You said you can just hear it if it is out of gear. But can you hear it if you are stopped and depress the clutch, so there is no drive to the box.If it goes completely when the clutch is depressed then it must be the box.
Probably not this but easy to check -
Are the bushes that hold the gearchange mechanism on the back of the gearbox OK. The bushes on our car had rotted away entirely which meant that the mech could hit the propshaft UJ. The clonking was not especially loud though it did vary depending what gear was selected.
As I said probably not but at least cheap to fix if it is.
Are the bushes that hold the gearchange mechanism on the back of the gearbox OK. The bushes on our car had rotted away entirely which meant that the mech could hit the propshaft UJ. The clonking was not especially loud though it did vary depending what gear was selected.
As I said probably not but at least cheap to fix if it is.
If it's the box will this fit;
www.pistonheads.com/sales/83743.htm
www.pistonheads.com/sales/83743.htm
toltec said:
Probably not this but easy to check -
Are the bushes that hold the gearchange mechanism on the back of the gearbox OK. The bushes on our car had rotted away entirely which meant that the mech could hit the propshaft UJ. The clonking was not especially loud though it did vary depending what gear was selected.
As I said probably not but at least cheap to fix if it is.
Are the bushes that hold the gearchange mechanism on the back of the gearbox OK. The bushes on our car had rotted away entirely which meant that the mech could hit the propshaft UJ. The clonking was not especially loud though it did vary depending what gear was selected.
As I said probably not but at least cheap to fix if it is.
I was going to suggest this but when I spoke to Mike he said the noise was there at idle...
Gonna try and get the car on a ramp asap to have a good poke around underneath. Maybe on the weekend.
As I was saying to Ian last weekend about three miles before the knocking became evident the car in front ran over a big hard plastic sheet of perspex or something which duly flew up and vanished under my car. The plastic then duly hit something underneath and basically shattered out the back in a thousand bits - well I was giving it some beans at the time!
Just wondering if anything has got stuck someplace or damages the downpipes / manifold gaskets or something - Basically until I have a good look I am in denial that its the gearbox or engine! ;-)
The noise, just to clear things up seems to be in time with the wheels, not something occasional under load but a constant loud tapping.
Mikey (ever hopefull) B
As I was saying to Ian last weekend about three miles before the knocking became evident the car in front ran over a big hard plastic sheet of perspex or something which duly flew up and vanished under my car. The plastic then duly hit something underneath and basically shattered out the back in a thousand bits - well I was giving it some beans at the time!
Just wondering if anything has got stuck someplace or damages the downpipes / manifold gaskets or something - Basically until I have a good look I am in denial that its the gearbox or engine! ;-)
The noise, just to clear things up seems to be in time with the wheels, not something occasional under load but a constant loud tapping.
Mikey (ever hopefull) B
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