Gearbox noise in 6th & 7th, C250 W204 M271 - 722.9

[Adywheels]

Hello all

So i got this weird rumble which at first i thought was a wheel bearing on its way out but it wasn't too loud at the time, but the other day after a 2 hour motorway drive it got louder, Ive discovered it's only when the car is in 6th & 7th gears so above 65mph > as I tried all sorts of speeds and gears, if i use the paddle shifts and drop it into 5th the noise goes away even at 70mph, so i think maybe an internal issue with those gears

Now it happens anytime i get to like 65mph and above where the car goes into 6th & 7th, but drop to 5th noise gone ?!?

It changes gear and drives smoothly in all gears except for this loud rumbling bearing noise in 6th & 7th which i can also feel through the gear shifter.

I got under it today and there are no visible leaks i also removed & checked the rear gearbox engine mount which look fine no cracks of splits in the rubber parts so i doubt its a mounting vibration like forum posts have said who had this same issue?

I've seen it is the deeper new style sump with the larger oval divets, so blue oil and filter are required, which i will get from Merc this week and do an oil change ASAP.

I'm not sure when it was last serviced TBH, I have no paperwork for it, the car has done a lot of miles 170,000 !!

Anyone else got any suggestions please?

Thanks in Advance

 

[Bay Leaf]

I would get it scanned, preferably by an independent Specialist and see what codes come up.

 

[Adywheels]

I would get it scanned, preferably by an independent Specialist and see what codes come up.

Hello, thanks for your reply, we have scanned it and nothing comes up, now i'm 99% sure it is the gearbox bearings :0 . just bought a lower mileage one with warranty, waiting for it to turn up so i can fit it....Oh Joy.... Will report back

 

[Adywheels]

New gearbox & torque converter fitted… and still the same loud rumble in 6th &7th !

So checked out the Prop bearing add it’s seems to have play in it, just received the new one so will fit it on Saturday and it if this fixes the loud noise

 

[Adywheels]

UJ on prop shaft is very bad, its stiff & notchy, so i fitted another one with another bearing and STILL HAS THIS NOISE in 6th & 7th gears only ..

So now its had a the following - torque converter, gearbox, complete prop shaft and still i have loud humming noise when in 6th & 7th only

Im working down the drive train! I suppose next i change the diff?? both rear wheel bearings?? I just dont see how these could only be noisy in the top 2 gears and silence in all other gears at the same speeds !!

this thing is killing me

 

[Adywheels]

for anyone who has this issue in the future... it was the front engine mounts causing all the problems, inside the mounts the rubber has completely collapsed, changed them and now its quiet as a mouse in 6 & 7. unbelievable ! its also much smoother through all the gears and at tick over

 

[malcolm E53 AMG]

In fault situations like this it always makes me feel that engine and suspension mounts should have a manufacturer’s recommended check/change interval

 

[Wighty]

for anyone who has this issue in the future... it was the front engine mounts causing all the problems, inside the mounts the rubber has completely collapsed, changed them and now its quiet as a mouse in 6 & 7. unbelievable ! its also much smoother through all the gears and at tick over

Jesus buddy , what did that lot cost ?
At least you are sorted for the next few years now