Driveline Shunt

[mchristyuk]

I've noticed quite a loud driveline shunt type noise coming from my car and was looking for peoples thoughts?

Car is a 4200 CambioCorsa and produces a significant clunk from the rear when going on/off throttle below about 25mph. It doesn't happen every time, but most times.

There is no noise noticeable above 25/30mph and there's no vibration and gear changes are fine whether banging through at the redline or slowly changing at more moderate speeds. Bouncing the car up and down or driving over bumps makes no noise... so suspension it is not. I've also checked all the brakes and they are fine.

I jacked the car up at the rear at the weekend and turning either rear wheel produced a clunk from the diff.. but then I'd kind of expect that.

I've read that these cars can suffer from driveline shunt at slow speeds, but this is much louder than I'd really expect.

So as far as I can see it's one of the following:

1) Perfectly normal.. buy a louder exhaust.
2) Shaft going from diff to wheel playing up
3) Main prop shaft to diff, either joints or loose bolts
4) Knackered diff

On my 3200 the main prop shaft was easily visible and it was quick to check that the mounting bolts were tight between shaft and diff (and in my case they weren't). The 4200 seems to run the propshaft in an outer tube.. a) Are there any bolts to check and b) How do you get to them inside the torque tube if there are?

Cheers!

Mark

 

[CatmanV2]

I'd look at 3 first. I think there have been some reports of bolts working loose.

1 seems unlikely.
4 would probably produced more symptoms, but I could be totally wrong.

C

 

[mjheathcote]

Don't forget with the 4200 we have a transaxle, not a traditional engine-gearbox-propshaft-diff, but engine-torque tube-gearbox/diff.

 

[mchristyuk]

Chaps,

Yes I'd be leaning towards the main propshaft.. however I don't see from the diagrams how you can get to it and how the ends of it attach to the transaxle? They seem to be hidden in some kind of outer tube...

Cheers

Mark

 

[mchristyuk]

Ok... ignore my last post. It appears there is no propshaft attachment like the 3200, the shaft itself slides into a splined coupler. The only bolts appears to be the outer torque tube.. which I guess could clonk if it's come loose.



Cheers

Mark

 

[spn]

I'd have though if it was driveline shunt, you'd notice it going through the gears and especially going on / off throttle at higher speeds.

The 4200 uses a plate type LSD so it could just be the cross shaft or cams moving as you apply power / coast - I doubt if the diff has much preload.

Cheers,

Simon

 

[alfatwo]

It's excessive backlash play in the diff crown wheel/pinion shimming that's causing the shunt.. the heavy click clack sound when you lift off or change gear

Same as on the 3200GT manual...I've had a diff in bits for the last few months looking for a solution, no parts available as usual...looks to me like an old ZF multi plate diff but with Maserati stamped on it!

Dave

 

[mchristyuk]

I'm pretty sure it's not the normal backlash play causing the noise.. it's almost embarrassingly loud at times.

One thing I forgot is that sometimes it does it even once everything is "loaded" and we're under way.. so say about 1 second after acceleration has started there will be this clonk.. but only under 30mph..

I'm leaning to something having come loose underneath... will have it up in the air on Thursday and give everything a check.

Cheers

Mark

 

[Fat Arnie]

It could be a failing bush/balljoint in the suspension - is the clunk worse after braking/lifting off?

Also on other cars (with AP racing brakes!) I have seen this from brake pads that can move in the caliper housings.

 

[mchristyuk]

It could be a failing bush/balljoint in the suspension - is the clunk worse after braking/lifting off?

Also on other cars (with AP racing brakes!) I have seen this from brake pads that can move in the caliper housings.

Hi Arnie,

Doesn't sound like a suspension joint and the suspension was given the thumbs up by Autoshield only a month ago. It sounds central to the car (and metallic).. it will do it without touching the brakes..

Cheers

Mark

 

[safrane]

Any chance the sub frame is loose?

 

[mchristyuk]

Any chance the sub frame is loose?

Yep

To be fair at this moment in time there's a chance that it's anything.. or nothing and I'm just being paranoid

Car will be up on the ramps on Thursday so all bolts will be getting checked!

Mark

 

[mchristyuk]

Ok so a small update on this.. I'm aware that these cars have a bit of slack in the diff and driveline shunt at stop start speeds.. and 1st to 2nd or 2nd to 1st can be a bit clonky.. but this was driving me up the wall because under 30mph I could play tunes with the rear of my car and application of the accelerator.

Going over speed bumps or round corners the car was silent.. it was purely acceleration/deceleration related. Everything on the car was in good order and tight when checked on the ramps. There was a suggestion it could be the lower shock bushes.. but on inspection they were fine too.

I was convinced it was "torque" related and therefore one of the twisty bits.. so the axles and universal joints were my chief suspect, however a few things started to fall in place over the past week which I hadn't really managed to "2+2=4" them...

Firstly going up hill it didn't do it. Only on the level.

Secondly it was audibly coming from the right hand side of the car. If I put the passenger window down it sounded just like it was coming from the rear somewhere. Put the drivers window down and clonk... clonk.. clonk...

I bet you can see what's coming...

Tonight I had to tighten up the connectors on the 12v battery as they had been bodged at some point in their former life (or from the factory.. who knows!). When I was torquing them down I noticed the battery shift. Hmm.. The battery clamp was tightened down as far as it would go and the strapping appeared tight, however I could quite easily slide the battery forwards and backwards. You have to be kidding me.... So I stuffed a rag under the strapping as a temporary fix and.. low and behold no more clonking when I play with the accelerator once on the move.

Shoot me.

Mark

 

[mjheathcote]

Excellent conclusion though!

 

[Contigo]

Ok so a small update on this.. I'm aware that these cars have a bit of slack in the diff and driveline shunt at stop start speeds.. and 1st to 2nd or 2nd to 1st can be a bit clonky.. but this was driving me up the wall because under 30mph I could play tunes with the rear of my car and application of the accelerator.

Going over speed bumps or round corners the car was silent.. it was purely acceleration/deceleration related. Everything on the car was in good order and tight when checked on the ramps. There was a suggestion it could be the lower shock bushes.. but on inspection they were fine too.

I was convinced it was "torque" related and therefore one of the twisty bits.. so the axles and universal joints were my chief suspect, however a few things started to fall in place over the past week which I hadn't really managed to "2+2=4" them...

Firstly going up hill it didn't do it. Only on the level.

Secondly it was audibly coming from the right hand side of the car. If I put the passenger window down it sounded just like it was coming from the rear somewhere. Put the drivers window down and clonk... clonk.. clonk...

I bet you can see what's coming...

Tonight I had to tighten up the connectors on the 12v battery as they had been bodged at some point in their former life (or from the factory.. who knows!). When I was torquing them down I noticed the battery shift. Hmm.. The battery clamp was tightened down as far as it would go and the strapping appeared tight, however I could quite easily slide the battery forwards and backwards. You have to be kidding me.... So I stuffed a rag under the strapping as a temporary fix and.. low and behold no more clonking when I play with the accelerator once on the move.

Shoot me.

Mark

Lol so it was a hearing issue which clouded your seat of the pants dyno

 

[philw696]

Has to be the wrong battery fitted I'm guessing as I haven't seen that before and potentially dangerous.

 

[mchristyuk]

Has to be the wrong battery fitted I'm guessing as I haven't seen that before and potentially dangerous.

Hi Phil,

It's a Bosch S5 that's fitted, as recommended in these hallowed parts. It certainly wasn't going anywhere, it couldn't escape.. but it could slide forwards and backwards about 5cm..

I'm going to take another look in the day light tomorrow to see if I can see anything obviously wrong.. but at least for now I've shut up that infuriating noise!

Mark

 

[mjheathcote]

Mine has a Bosch S5 fitted.
When I changed the battery to the S5 the original battery clamp was missing, had to order the correct clamp from the main dealer.
The old battery was still secure, but it was a bodge job I wasn't happy with.

 

[mchristyuk]

Ok. Time to provide some full closure to this thread for anybody else who may experience weird drive line knock noises in future.

Whilst securing the battery got rid of the sickening "thunk" when accelerating/decelerating below 30mph there was still some kind of transmission click/clunk at maneuvering speeds which I really couldn't put my finger on. It was almost as if the diff had far too much slack in it.. once the load was taken up it was fine.. but on/off load up to about 20mph there was this odd click noise.. sometimes quiet.. some times louder.

The clue was in this thread here:
http://www.sportsmaserati.com/showthread.php/17502-Clinking-noise

However neither I nor anybody I spoke to could imagine that axle splines could make such a loud deep noise as they are so fine. Well my eyes were opened after hearing about Nissan 350Z axle click.. which is cured by taking them out and greasing the splines.. just like the thread above.. Below is a video of what it sounds like:
[video=youtube;Dmi4wy2ZP4s]https://www.youtube.com/watch?v=Dmi4wy2ZP4s[/video]

So today she went to my mechanic to have the axles out and cleaned/greased. However we soon discovered that the axle wouldn't be coming out without undoing some of the suspension arms. Now with it being so close to Xmas and the fragility of the arms we decided discretion was the better part of valour and the axle re-inserted and torqued back up.

I joked that undoing them, moving them in and out a bit then tightening them back up have probably fixed in anyway by distributing some of the rust about.

And I was right.

Car was blissfully silent all the way home.. well apart from the exhaust

Hopefully this can be helpful to others in future.

Happy days.

Mark

 

[DPS20K]

Glad you sorted it. I couldn't believe the noise mine were making before Emblem sorted them. People would turn and look as I pulled out of junctions it was that bad. Two years on and they are still totally silent.
Don't forget you need to use a new hub nut everytime you undo one.