Clonking!!!!

[MartinN]

Hi all, I'm looking for so e help please.

Last season I Haa a "off" at Lydon Hill. This broke the nearside rear hub, bent the swing arm mounts and broke the diff case and bent the nearside damper and damaged the propshaft
The car is back together, after raiding Spurs stock of spares.
I have though not got something right.
Drive takes up smoothly, gear changes fine and smooth but there is a wheel speed related clonking. Which strangly doesn't happen in reverse, or if lifting off the throttle. I have found an area where I can reverse at a decent speed to test this.
I am suspecting the diff or could it be the propshaft out of alignment. I have been over the rear beam, drive shaft bolts, prop shift Guibo and diff bolts, all tight. there is no change to the clonking on cornering.
I have done a full re Bush on 2 Zeds, and altough I'm clearly an amateur I think I can hold a spanner pretty well but this has got me scratching my head.
Parts replaced.
Rear beam, nearside swing arm, both polybushed, propshaft, both dampers, Diff.

Any ideas greatfully accepted

Oh I need the car up and running for this year's sprint/Hill climb season, my first outing planned for early May.

Take care good People.

TIA

 

[Pingu]

Did you split the propshaft?

 

[MartinN]

I replaced the propshaft as a complete item. I picked it up from Spurs, I dont think it had been split.

cheers

 

[MartinN]

The cadence of the noise sounds too slow for the propshaft tho, I thought maybe the centre mount, but it's a fiddle to get to that, exhaust off etc

 

[t-tony]

Is the drive shaft definitely the correct length? IIRC there are different lengths and it’s not a huge amount.

Tony.

 

[MartinN]

I believe so Andy Took it off a same year 2.0ltr, same model as mine.

MN

 

[Lee]

How are the wheel bearings and the bearings in the diff and the shaft between the two, I wouldnt think it would be the prop as they vibrate like mad when unhappy.

 

[MartinN]

Wheel bearings appear sound, I would expect a constant rumble from those if dodgy. Dont know about the diff, that's why I suspect It, but turning By hand it all felt smooth.
Cheers tho

 

[Lee]

Lift the car up n spin the wheels in the air, see what shes like with no weight.

 

[MartinN]

Hi Lee, yeah thought about this. I guess I should get the swing arms level to recreate the on road position. I have some 3 tonne axle stands to put the car on and a pair of trolley Jack's to lift the swing arms. Sadly no ramp or garage to work on/in

 

[Lee]

Personally I would do it with them hanging first. Done this many times in the shed. Then maybe with the arms lifted, just feels sketchy not lifting on a flat.

 

[MartinN]

Thnx Lee

 

[MartinN]

Bit of an update, but no progress. I have the car in the air, well enough for me to get under it safely.
Exhaust and heat shield off. I have checked, again, the gumbo, centre bearing and prop to diff bolts, all are as OK as I can establish. I have disconnected the drive shafts from the diff, both sides and checked the CV joints, no play there. I have give each rear hub a bloody good shaking. Spun the wheels by hand, nothing to give a clue as to the noise.
Another clue perhaps is as well as being speed related it does get louder with speed. But again not apparent in reverse. I'm stumped.
If anyone is passing my place or fancies a look please let me know, I can get get car mobile, if the weather is good in a couple of weeks.
Really appreciate comments so far. If anyone can suggest possible things to look at that would be appreciated
Thanks all, stay safe and happy Zedding

 

[MartinN]

That's Guibo, I can't get the grip of my spell checker

 

[Pingu]

Did you preload the propshaft centre bearing?

It needs to be pushed towards the gearbox by the correct distance. I think it's 5mm.

It sounds like you have checked everything for play.

Have you check the brake backplates? They can rattle and clunk. As can calipers and even brake shoes inside the disc.

You can run the car with the wheels in the air, but at the correct ride height (axle stands under the swing arms). I'd also have the front wheels on a ramp, so the car is more level. If you go above 30mph, the speedo will drop to zero. It will reset when you switch off and switch back on again. I'd be getting to last resort stage if I had to do this, but I have done it. The cause of my problems was the gearbox remote steady bar had been put on the wrong way around.

Worst case scenario would be a drop test. You use a plumb-bob at key points of the car to ensure the car is true and square.

 

[MartinN]

Thanks, I have thought about running the car, but the exhaust Is off, I dont mind making a noise but the locals may not be too tolerant. Checking the gearbox mounting came to me a little while ago, the car did take a hard side swipe, so that may have moved it.

 

[Lee]

Bit of an update, but no progress. I have the car in the air, well enough for me to get under it safely.
Exhaust and heat shield off. I have checked, again, the gumbo, centre bearing and prop to diff bolts, all are as OK as I can establish. I have disconnected the drive shafts from the diff, both sides and checked the CV joints, no play there. I have give each rear hub a bloody good shaking. Spun the wheels by hand, nothing to give a clue as to the noise.
Another clue perhaps is as well as being speed related it does get louder with speed. But again not apparent in reverse. I'm stumped.
If anyone is passing my place or fancies a look please let me know, I can get get car mobile, if the weather is good in a couple of weeks.
Really appreciate comments so far. If anyone can suggest possible things to look at that would be appreciated
Thanks all, stay safe and happy Zedding

Seeing as we're brain storming, if your getting the noise drving forward but not in reverse maybe we should think about the diff again.

Driving forward you would be knitting on one side of the crown wheel teeth and then in reverse the contact face will change, did you say you inspected those faces or at least get it checked ?

 

[MartinN]

Didn't Look into the diff, but I bought a second hand one. I guess it would be a good option. Never been inside a diff before tho. Would it be just remove the rear cover, after draining the oil of course. I have tried turning each output And the prop side I couldn't feel any rough Spots but then again there is no real loading.
Cheers Again

 

[Lee]

Yeah the Z3 diffs are very simple, support the case with a jack drain the oil and remove all the bolts including the main diff bolt. would be worth getting a new gasket first or at least some high temp sealer.

The oil colour should show anything sinister going on inside.

 

[MartinN]

Ta