knock knock knock from rear when accelerating

[123-jn]

hi folks, I am getting a sound from the rear like a cv joint on a front wheel drive car on full lock? coul this be a drive shaft joint? there appears to be no play in the shaft joints like I expected to find but a fair bit of play in the wheel bearing. Do these t25 rear bearings run with any play? or could this be the source of the knocking? Any experts out there?

[California Dreamin]

You were likely correct with your first statement......these rear engine rear wheel drive vehicles have drive shafts very similar to traditional F/W/Drive cars, with an inner and outer constant velocity joint each side.
So it is likely one or more of these is making the noise you describe.
You might be lucky and what you have is a case of very old solidifyied grease ..in which case you can remove each driveshaft, clean/examine each joint (1 inch paint brush in a tray with a inch of petrol) and if it isn't excessively worn, re-pack with fresh CV grease. In a lot of cases this will cure the noise as long as there was nothing obvious.

Martin

[Plasticman]

how have you determined play in the rear bearings as above but id still be interested
mm

[sarran1955]

Hello,

This might help..

http://www.youtube.com/watch?v=meTNBph3rUU

Other things to note are:

Use only OEM quality replacements, otherwise you'll be doing the job again within the year

Yes you do need good quality expanding circlip pliers

You will need a sturdy bench and vice..

Work safely, have fun.

Cordialement,

[ghost123uk]

Wheel bearings. Do these t25 rear bearings run with any play?

A tiny bit of "in out" play is acceptable but any discernible "rocking" play is not good.

As said = likely CV joint, but have you checked the tightness of the inner and the outer drive shaft flange bolts (usually "Allen" headed items) ? Quite common for them to come loose (and then break) on our vans.

[123-jn]

I have had it on ramps and checked the tightness of the cv bolts so sadly it isn't that (all torx headed) . Definitely no play in the joints so I think I'll have to remove them one shaft at a time and clean them up to see what the condition is like. The bearing is another story as it appears to be a longer job!! Firstly the brake drums are stuck on presumably by a wear ledge so I will need to hope the adjusters can be backed off!!
Thanks for your advice. The play on the bearing can be felt at the wheel rim by rocking the wheel top to bottom and side to side. Thanks for all the advice.

[123-jn]

strangely having just felt the bearings again, there appears to be more play top and bottom than side to side which doesn't make sense to my poor little brain. This is the same on both sides but the left from whence the knock comes has slightly more play. How peculiar!!

[Plasticman]

slight play is acceptable in 1 plane.
lets hope you dont have worn housings
mm

[col.decker]

I had an odd knocking on mine when I accelerated around a right hand corner. Turned out to be the radiator supply/return pipes knocking against the chassis. A couple of cable-ties later and it was sorted.

Its a long-shot but you never know ...

[Ian Hulley]

Having fitted our new silencer that knocked against the chassis on the offside as we went round left hand bends (French roundabouts etc) probably not your issue but appn something to bear in mind

Ian

[croc]

Hi all.
I have been wondering, after having CV bolts loose and sheared, whether the cause of the bolt fault might be that the CV joint is worn/pitted and causing a 'hammering' which loosens the bolts??
Certainly on mine, the side with loose/sheared bolts on the gearbox flange, the CV joint was badly pitted and needed replacing.
Not sure were to go with this!! - but I suggest that anyone finding a loose CV joint bolt should remove the shaft and check/repack - not just replace and tighten the bolts.
Anyone got any thoughts on this line??

croc

[CovKid]

Loose/Dry CV joints could well contribute to bolt failure but usually for bolt failure, there needs to be a chink in the armour in the form of one or more bolts that are not quite as tight as the rest or missing friction washers. From then on, joints can work loose over many days/weeks. There are some strong forces in play on driveshafts - to put it mildly.

You need to work out if the knocking is actually rhythmic in some way or more random. If rhythmic it will almost certainly be joints or hubs (including and up to wheels). If somewhat random, do not rule out shock mountings/bolts. They can look fine yet the smallest amount of movement at the mountings will be amplified considerably, producing an annoying clonking/tapping sound - usually worse over even moderately bumpy surfaces. Sometimes simply nipping up a mounting bolt miraculously makes the noise vanish, despite everything looking fine.

As mentioned, other things can knock including worn engine or gearbox mounts which cause the engine/transmission to twist a great deal and bring items in close contact with each other that under normal circumstances, should not.

I mention all this as 'mystery' noises from the back are often difficult to pin down and sometimes, no matter how experienced, the only way to completely eradicate one is through a process of elimination. Getting the vehicle in the air on a big ramp is very useful though!