hum from the rear of car
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Junior Member
Joined: Mar 2011
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From: SF Bay Area
2004 c 230K and 2014 SLK 250
hum from the rear of car
Hi, I have 05 c 320 coupe 6 speed, 75k on it recently when driving about between 60 to about 75 mph I hear a hum , when accelerate past 75 it seem to disappear and no hum before 60 mph, rear tires brand new continental dws, the hum is present when the car is under constant load meaning as soon as i let off accelerator it disappears. would the rear bearings cause this (no play there) but maybe just starting to wear out . Now I've jacked car in the air (front and back) and checked for play in wheel bearings, front had a little play which I corrected by re seating the bearing to no play(snug by hand and back off a bit), now no play on rear wheels. Also checked center bearing on drive shaft( seems ok) however when gabbing the drive shaft and twisting it back and forth there seems to be a small amount of play between front of ctr bearing and aft of it .(Two piece drive shaft) U joints appear to be ok. Diff oil level good, did not changed fluid there yet. Any ideas -- did I miss anything?
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Joined: Jun 2008
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
How loud is this noise? These cars do have a slight harmonic in that speed range.
Otherwise it could be the diff pinion bearing having lost preload.
Otherwise it could be the diff pinion bearing having lost preload.
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 23
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From: SF Bay Area
2004 c 230K and 2014 SLK 250
ok the noise is bit annoying somewaht loud ,so I just lited the car on 4 jack stands changed diff fluid, put the car in dyno mode
and let it rip, up to 60 to 75 mph and there is a sound i pinned pointed either to half shafts or the diff, but the sound seems to concentrate in the center
. Im afraid it may be the diff. Is the diff pinion bearing preload adjustable? or just replace the whole diff assy. Thanks for your expertise Glyn . I often read your posts to answer my question about t/s problems.
and let it rip, up to 60 to 75 mph and there is a sound i pinned pointed either to half shafts or the diff, but the sound seems to concentrate in the center. Im afraid it may be the diff. Is the diff pinion bearing preload adjustable? or just replace the whole diff assy. Thanks for your expertise Glyn . I often read your posts to answer my question about t/s problems.
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Joined: Jun 2008
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From: Llandudno, Cape Town, South Africa
late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
Preload is set up when you build a diff new or replace the pinion bearings.
You might need to rebuild or replace the diff if that's where the noise is coming from.
The harmonic I'm talking about is very quiet. You have to listen carefully for it. Sounds like yours is loud.
You might need to rebuild or replace the diff if that's where the noise is coming from.
The harmonic I'm talking about is very quiet. You have to listen carefully for it. Sounds like yours is loud.
MBWorld Fanatic!
Joined: Dec 2006
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From: Toronto, Canada
2019 C300 Wagon; '75 Triumph TR6; previous: 2004 C230 6spd sold after 17 years of driving
could be the parking brake (do a search on this) the lever binds (under the rear seat) and will not completely release. This will make and incredible noise when up to speed and sounds like something is wrong with the diff, bearings or half shafts.
Also could be the center bearing hanger of the drive shaft, my neighbour's C had this issue and made a hum at high speeds
Also could be the center bearing hanger of the drive shaft, my neighbour's C had this issue and made a hum at high speeds
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 23
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From: SF Bay Area
2004 c 230K and 2014 SLK 250
ok tnks for the help, I changed the diff fluid , man was it black... anyhow no difference, also did fluid in my other c 230 and the fluid was just light brown. Does these cars have LSDs , maybe clutches starting to wear.
I ll look at the parking brake possibility , parking brake pedal travel seems to be very short( I mean it works so good that you just have to press it a little to set it) .
I ll look at the parking brake possibility , parking brake pedal travel seems to be very short( I mean it works so good that you just have to press it a little to set it) .
