Faulty New Diff Bush(S) = Diff Damage?

[Spoony]

I recently had 3x new diff bushes, all Superpro with the 'comfort' centre bush.

In less than 1000kms I started noticing some nasty clunking, vibration and shudder (ie like a tailshaft inbalance) through the car. Turns out a faulty centre bush allowed the inner sleeve to seperate from the bush, inturn allowing the centre to flog out, destroying the other bushes and allowing the diff to shift backwards.

It's since been replaced however there is still on/off/engage rear end noise and to some degree clunk, but it's different now. It sounds almost more like the diff it self (backlash). I also now notice some diff whine, where previously this diff was dead quiet.

Obviously I'm going back to the shop again, but I'm curious as to weather having the diff shift out of place/allignment and being driven under power (this is when I first started noticing the oddity) could have damaged the diff or maybe some other components of the driveline?

[senna_T]

Check that the side diff bushes are installed correctly and the diff is located properly. If the side bushes are installed too far forward, the diff is pulled forward and in turn it destroys the rear diff bush. This will also cause a great deal of Noise, Vibration and Harshness (NVH) transfer into the car because the diff is touching the sub-frame (cradle).

[Ralph Wiggum]

+1 ^ what he said.

[Spoony]

I'm guessing it's something installed wrong, going back to them this arvo as its pretty bad. Just hope hasn't stuffed something else (ie diff, drive shaft bearing, coupler rubber etc?).

[Spoony]

I'm a little more knowledged now. Originally the suspension mob installed 3x Superpro bushes, all the new 'comfort' (voided) type. I thought it was just getting 1x superpro comfort and 2x factory side bushes.

Upon the first failure Superpro was down to their workshop in the hour with new bushes. However what they resupplied and said to fit were 1x same Centre bush but 2x solid side bushes. I've been told there are no side 'comfort' bushes available in country. (sounds to me like a pulled product due to issues maybe??)

So now I've been told that these solid bushes will transmit more NVH though the car. I made the point that the first time I picked the car up the driveline 'felt' tighter than now even and was dead quiet.

They did drive it and agree on the noises. It's pretty pronounced. Just running from R to D now gets a clunk. When I say clunk it's almost more of a audible knock (clicky almost) . It is apparent in any on off throttle, even in "D" driving very cruisey with normal up and down shifts that the ZF does one can hear and sometimes feel it. Ie come up to the lights it might shift down or whatever and you'll hear it. A taxi's got nothing on this. haha

Under the car while loading the diff up in both directions I was amazed how much it moves. To the extent that the centre bush comes away from the outer hole either top or bottom depending on the load direction. They didn't seem worried about this but is this normal? I just can't see how a bush is allowed to move anywhere but within the bush itself, surely that will allow friction wear and possibly even road muck to get in?

Also noticed while checking the diff backlash it seemed a tad much, but then it was realised both inner CV's have some play. Ie the dif has engaged and moved the splines on the CV"s not the axel. How much play do these normaly have? I thought CV's have basically none.

What I'm wondering here is if the noise is from the CV's taking up. In which case I can only put it down to them being damaged from the prior stuffed bushes. The side bushes were apparently totally flogged, centre split, so who knows how much twist/whatever the diff could move under power, possibly putting these CV's at an angle/stress not within spec?

The reason now I think it could be drive train noise is it can happen with minimal load, so the diff movement would be minimal.

If the drivetrain was already like this however, it would have been present previously, not immediately appeared after the bush failures.

Oh, too boot now I've now got diff whine in the cabin. Previously dead quiet (I've been in the back of the car as a passenger on long highway trips).

In short, the first time I picked the car up it was dead quiet, no whine, no knocks or clunks in the driveline/diff/mountings. The are going to get back to me on what to do, but in my opinion it should be fixed back to the same. I don't think I'm being unreasonble?.

Given your experiences, keen to hear your opinion senna. Oh and the diff is 'located' in the right spot and visually can not be seen to hit anywhere.

[senna_T]

In short, the falcon driveline is noisey and has quite a bit of free play from the factory. The harder competition spec bushes that they have fitted are transferring all that noise through to the cabin - the factory rubber or comfort spec super pro bushes hide alot of this noise.

We spent a lot of time with fulcrum developing the comfort bushes and I run them in my own car, there are still some clunks in my car, but that has more to do with the CVs and Diff being sloppy!

[Spoony]

Thanks for that. So you run the all 3x comfort bushes in the T? It's lasting ok? I was very happy with it when I first picked it up till it when to poo. Not happy at all now. Given there is zero 'comfort' side bushes available at the moment, what combo would you recommend? The comfort centre bush + factory side bushes? From what I've read the factory side bushes usually hold up ok until the centre flogs out then kills the side ones.

The car only has 290rwkw, is a daily really doesn't cop a hiding that often. 145,000kms on it with original bushes, 30,000km with my driving and 290rwkw and they were not totally trashed says something I guess.

Edited 05/10/11 10:10 PM by Spoony

[wa g6et]

I too have 3x comfort bushes and what little noise I get it more akin to noisy tyres really and as soon as I open a window or turn the stereo on I can't hear it. As for clunks, I only get a clunk when I go full on the gas and lift off suddenly, on factory bushes any lift off at any real amount of throttle would give clunks.

Given you have got what you did out of factory bushes, I'd be inclined to go comfort centre, factory sides. I'd think that would be a nice compromise.

[Spoony]

Yep I totally agree, and this is what the suspension shop put in to start with. After the failure (due to faulty manufacture) Superpro supplied them with a comfort centre but soild side bushes, which is more than likely now presenting all these problems. I'm just going to tell them to pull it out again and either fit new factory side ones, or new comfort ones.

The cars output is only a little bit more than a stock new FPV, and I don't flog it heaps (as per getting 145,000 +kms out of the original stuff) so I would assume full comfort bushes should last even longer than stockers, just not as long as the solid ones.

If there is still a knock then, proves damage has been done also I guess.

[senna_T]

Comfort bushes have been in my car for around 15,000 k's now, no dramas!

If there are no comfort bushes available then yes, the factory sides should be ok as long as the rear diff bush has been changed. If you had much more power or flogged it daily then I would not recommend the factory bushes at all.