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The mkiv Supra Owners Club

Hard knocking from the rear


seba

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Ok a mate just called me in panic. He was driving his supra at 50m/h (he is a very decent driver) when a hard knocking started from under the car at the rear. He described it as a hammer being hit from under the backseats or somewhere behind the frontseats with a bit of grinding. It is a constant noise and the harder he drives the louder it gets. Also releasing the gaspedal brings the noise. To get the noise a bit under control he kept a bit of presure on the gaspedal, so not giving too much gas but not letting it loos either, that's when there is the least banging noise. He drove the car home at 10 m/h this way 5miles further. Back home he went to ly down under the car and says the cardanshaft (or how do you call it in English) seems ok, or maybe he just can't see it.

What could this be? He says the car is undrivable and the noise gets overwhelming. Could this be the differential? Has anyone had this same issue? I know him very well he drives like a grandma so it cant be he forced something.

Any advice very welcome ! :rolleyes:

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Guest Roger NE

When diffs start wearing out they normally GRADUALLY start making a whirring/grinding noise

 

Does the banging sound as if someone is hitting the underside of the car? If so, I recently had a similar noise on my Mk3 - it was the propshaft centre bearing

 

It's VERY expensive to replace, so cheapest/easiest option is to just replace the complete propshaft with a secondhand one from a breaker (seeing as they very rarely fail)

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If it's that loud I very much doubt it's the exhaust just swinging around a bit - I had that on my mondeo and it was a slightly annoying 'donk' when I went over bumps.

 

This sounds to me like the differential, I had a tooth strip off in a Granada once and it sounded like someone repeatedly hitting the underside of the car with a lump hammer.

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No it can't be just the exhaust he checked it. If it's the propshaft centre support bearing is this something i can see without thaking the entire propshaft out of the car? Or what should i be looking for? I hope it's just the differential since i have one lying around for some time and could use that one.

How much do propshafts go for? Not new just secondhand ofcourse.

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Get the car up on stands or preferably on a ramp and it should be pretty obvious if its a problem with the prop.

 

The center bearing is held to the bottom of the car with 2 bolts so see if thats loose, also see if the prop

has any side to side or up and down movement in it, if the bearings gone then again it should be pretty obvious.

 

Also check the u-j joints and where the prop bolts to the diff, if its none of those

then driveshaft cv joints or diff are next on the list

Edited by Dnk (see edit history)
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Get the car up on stands or preferably on a ramp and it should be pretty obvious if its a problem with the prop.

 

The center bearing is held to the bottom of the car with 2 bolts so see if thats loose, also see if the prop

has any side to side or up and down movement in it, if the bearings gone then again it should be pretty obvious.

 

Also check the u-j joints and where the prop bolts to the diff, if its none of those

then driveshaft cv joints or diff are next on the list

 

Ok thx very much for the help. The 2 bolts holding the center bearing are ok. He is going to try to get the car on stands now and start the car to see what he can hear/see. He did say now that when he left MOT yesterday and turned to the right he could hear something grinding, this happened twice and after that the knocking started.

 

Sorry to see this hasn't been resolved. On a lighter note, my misses saw the thread title and thought you were being rude!

 

:taped:

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Driveshaft loose, cv joint failing/failed, wheel bearing, brake caliper, broken damper/spring, diff,

loose subframe, wishbone ball joints, etc etc

 

If he can get it on stands or a trolley jack then rotate the wheel, check wheel bearing, take

the wheel off then you can see pretty much everything on that corner without getting

under the car.

 

As i said it would be much better on a ramp and safer

Edited by Dnk (see edit history)
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  • 2 weeks later...

Ok i went to take a look at this supra today, the problem was really silly. He had new tyres fitted to his car and after i took the wheel and the brake + brakedisc of today from the side where the cluncking was coming from, and putting it all back together, the noise was gone. A lot of drama for nothing.... Just wanted to post the "solution" incase anyone in the future might start panicking about nothing, and a big thanks for all the advice and help given :thumbs:

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