Knocking on acceleration and deceleration

im really happy that it has made it better than it was though
 
One Spanner Frank said:
Drive shaft flex disc.
Click to expand...
its not that, but cheers for your help, its after the diff, the drive to the wheels, it looks like there are felx disks either side of the diff, connected to the shafts that go to the wheels. im thinkng the slack is there
 
apart from its not its not flexing, they just clunks a little when you turn it by hand... its strange, i need to look at a blue print diagram of the diff to understand it
 
Hi Pete, to check the driveshaft joints for play you need to hold the larger parts at the joint housing and try to turn the thin part of the shaft. There will be slight movement but very little. Also there is some lateral movement (end float) in the shafts to allow for lengthening and shortening of the shaft as the suspension moves up and down. Might be worth checking that the rear hub nuts are tightened properly too.

Tony.
 
Does it improve with heat ? The diff will have some backlash/play when cold and when it heats up and expands it takes it out.
If it is excessive it will knock it has to have backlash as without the heat would cause it to weld itself together.
A longer drive may be needed to see the full benifit.
 
Think I'm late to the party,

1) Diff oil, you need to know if its an LSD or standard, you can find that out with the VIN this will depend on what oil is needed (might need a modifier)

2) Clonk, looks like you've gone a similar way to me. The backlash on the pinion gear will be to blame, Unfortunately this is a secret so it has to be reset by a diff specialist. My M did the same thing which cost me £280 for the lot, that included some other bits too.

Lee
 
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t-tony said:
Hi Pete, to check the driveshaft joints for play you need to hold the larger parts at the joint housing and try to turn the thin part of the shaft. There will be slight movement but very little. Also there is some lateral movement (end float) in the shafts to allow for lengthening and shortening of the shaft as the suspension moves up and down. Might be worth checking that the rear hub nuts are tightened properly too.

Tony.
Click to expand...
i shall do just that! and i didnt check the rear hub bolts so ill do that too, cheers
 
Antm72 said:
Does it improve with heat ? The diff will have some backlash/play when cold and when it heats up and expands it takes it out.
If it is excessive it will knock it has to have backlash as without the heat would cause it to weld itself together.
A longer drive may be needed to see the full benifit.
Click to expand...
ive not taken if for a good long run yet since doing the bracket baring, but it never improved it before.... theres potential that it does, ill go for a run motorway run soon to warm her up and ill be able to tell then.
 
Lee said:
Think I'm late to the party,

1) Diff oil, you need to know if its an LSD or standard, you can find that out with the VIN this will depend on what oil is needed (might need a modifier)

2) Clonk, looks like you've gone a similar way to me. The backlash on the pinion gear will be to blame, Unfortunately this is a secret so it has to be reset by a diff specialist. My M did the same thing which cost me £280 for the lot, that included some other bits too.

Lee
Click to expand...
right, ill look into that, is there anything i can do to test if it is actually that?
 
If you prop the car up Pete and get under if you rotate the prob shaft by hand you will probably feel the slack then the pick up of the rotatation. The slack is the clonk as the gears engage and take up the slack a modified driving style can help but as Lee as said its probably the back lash and this is set within the diff with shims etc.
But if you move the prop left to right by hand you will feel the movement before the wheels spin.
Again the diff oil is different in the 2.8 as most have an lsd so worth checking.
 
Antm72 said:
If you prop the car up Pete and get under if you rotate the prob shaft by hand you will probably feel the slack then the pick up of the rotatation. The slack is the clonk as the gears engage and take up the slack a modified driving style can help but as Lee as said its probably the back lash and this is set within the diff with shims etc.
But if you move the prop left to right by hand you will feel the movement before the wheels spin.
Again the diff oil is different in the 2.8 as most have an lsd so worth checking.
Click to expand...

cheers, ive pretty much handed this over to my dad now as its getting a bit too much for me to work out... he says it isn't this, as there isn't any play when you do this... ill let you know when he knows for certain what it is. he thinks its the CV joint half shafts... as I said, its getting a it too technical, so its in his hands now hah

just to add. I drove up to Liverpool yesterday there and back, which was a 2 hour round trip, it ran really well, but the knocking was there even when the car was well and truly up to temp. everything is pretty damn good apart from this knocking!
 
What was the latest on this....seems to have come to a halt. My car has the same clunk issue like a little nudge in the back.

Also for those of us not technical what are 'cush' drives?

...and a propshaft 'donut' coupling?
 
I had this and after changing the diff mount which can be done on the car it has removed it completely.
The clunk is there on the drive taking up the slack the thud is the diff moving under load it is more of a gently engagement now removing the thud
 
Thank you......How easy was it to change the diff mount. Is it something that can be done at home or are specialist tools needed?
 
You can do from home the powerflex one can be installed easily by hand. The bush center will likley fall out the most awkward bit is cutting a slot in the metal outer ring with a hacksaw to remove but its doable.
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:thumbsup:
 
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