Five garages and no one knows what is wrong.

[RupertC]

The AA, my regular garage, a Merc specialist, a brake specialist and a Merc engineer have all looked at my car and agree there is a real issue, but none know what it is. The latest idea is that it is a gearbox issue. Does anyone on here have an idea or how I can diagnose the issue?

The Symptoms.
Under braking there is a very noticeable vibration through the steering, it is also present but to a lesser degree in the pedal and seat. It is present at all speeds. This feels like it is the front of the car.
Under braking there is a tyre noise that sound like a flat tyre. This noise also comes when the car has been on a long trip 2hr+ when just cruising along over 50 mph.
When descending a steep hill and when the car is on cruise control, I can feel that the car is being held back. I.e. it is as if the gearbox is constantly trying to decelerate the car. (the odd thing is how noticeable this is).
About 12 months ago I stopped to get fuel and when I started the car again, the gears would not engage. I restarted the car and the issue did not repeat itself (This may not be relevant).

Work done but with no effect or negative effect.
On the Front - New AMG discs (replaced twice), pads, bearing, joints on the various arms that connect to the wheel. - no effect
New tyres, balancing - no effect
Attached to the Merc computer - Old faults were cleared and it was re tested. No faults on any systems at all. The car was retested 6 weeks later, still no faults.
The car just had a type A service, the gearbox oil was dirty. The filters were changed etc. After this last service the problem is worse. Now my wife recognises the problem and says her passengers have noticed it too.

The car is a C Class 3.0 C320 CDI Avantgarde SE 7G-Tronic 4dr circa 2005/6 with full service history and 144,000 on the clock. In all other respects the car is great.

Thank you for reading this and trying to help.

 

[Aero]

Engine and gearbox mounts? If all badly worn/ then transmission misalignment issues possibly? Shot in the dark there but may be worth investigating?

 

[Bullyfooked]

Does this vehicle (mine do) have a propshaft center bearing?

 

[renault12ts]

If you turn the ESP off does anything change?

If you haven't tried this then do so and report back.

 

[Lyserman]

+1 on all the above and my 2p worth.
Olly at PCS recently told a tale of woe about gear selector problems and it turned out to be engine mounts.

Did they check the runout on the new discs? This is what I would check first if I had vibration under braking.
The hubs do get rusty and need a very good clean with a flapwheel when fitting new discs.

Worn ball joints can also give these symptoms. Have all of these been checked?

The cruise control is trying to maintain the speed you have selected and this is normal when going downhill.

 

[whitenemesis]

As above, if you had new discs fitted they have to make sure the hub face is scrupulously clean.

 

[Jonesy161]

Trying not to over complicate your issue......I had a very similar problem with a newish focus st, went back to fords three times without success, despite changing bearings, discs and pads all under warranty.
On the fourth time back, they took the hubs and knuckles off and swapped them off another car, together with the shocks. Car was perfect.....they put it down to a side swipe against a kerb etc, one hub, knuckle and shock were found to be very slightly out of alignment.
Good luck.

 

[jsl1991]

Have you had the tracking done? I'd try that. I had a bad vibration when braking on a corsa years ago, I swapped loads of brake and driveline parts for new with no result, Got the car aligned and it went away


Sent from my iPhone using Tapatalk

 

[jp 1]

Had same sort of problem on my sprinter van , replaced Propshaft centre bearings ,sorted.

 

[ioweddie]

Buckled wheels?

 

[markjay]

This might not help you.... but here it is anyway:

Had similar problem on a previous car (not MB).

Decided to replace the front discs and pads, and the front wheel hubs and bearings.

Initially this fixed the problem, but it came back a couple of months later.

At that point I suspected a front suspension component. I bought new lower wishbones, but eventually sold the car before I got around to replace them.

Good luck.

 

[merc85]

I had a similar issue with a Volvo, It had aftermarket wheels which needed spiggot rings fitting.

the rears did, But the fronts didnt, and vibrated exactly like a out of balanced wheel

 

[markjay]

This might not help you.... but here it is anyway:

Had similar problem on a previous car (not MB).

Decided to replace the front discs and pads, and the front wheel hubs and bearings.

Initially this fixed the problem, but it came back a couple of months later.

At that point I suspected a front suspension component. I bought new lower wishbones, but eventually sold the car before I got around to replace them.

Good luck.

To clarify - mine vibrated only when braking at motorway speeds. Even with mild braking, but the speed had to be 50mph+ for this to be noticeable.

 

[wu56Shoozz]

It would be an expensive gamble to replace the gearbox and find out its not that.. I have heard of gearbox vibrations mainly in Audi's & VW's but not in a Merc, their usually indestructible.. I'd be looking at propshaft & mounts before discrediting the box.. Where are you located? I have exactly the same car...

Just looking again at some of the replies.. rotate the wheels front to back left to right and report back, I had a similar issue on an Alhambra and it turnout the rims were buckled very slightly...

 

[Auto-mobile]

Engine mounts, gearbox mounts or something to do with the prop.

With cruise control on and going down a hill it will hold back, it's doing its job trying to maintain your set speed.

 

[wu56Shoozz]

^ Very True..