I have noticed a clunking noise for quite a while in my '72 250 - noticeable when I put the car in gear and sometimes while driving (usually when slowing down and accelerating - not while I'm cruising). Got the rear tires up on some ramps and had a friend shift the car in and out of reverse and I finally isolated the noise. It is clearly coming from the rotating of the flex disc - when you put the car in reverse the driveshaft rotates and the rear of the car comes up some. The flex disc 'looks' fine (I changed both front and rear and put a new center bearing in when I got the car, about 3 years ago). The clunk may be coming from inside the differential, but I'm not sure???

I know that I have never changed the differential fluid - or even checked it for that matter. Could it be as simple as that?

Anyone ever had a similar problem - any ideas?

Ryan

1972 250 W114

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

My clunking 250/8 was tracked down to the sway bar bushings. Or rather, the complete lack of bushings. The axle wraps up when put in gear and the connecting rods would go clunk.

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

That's what I thought it would be as well - but the noise is clearly coming from where the rear flex disc connects to the differential. I just can't tell if the flex disc is bad, or if it is coming from inside the differential itself.

ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

if you put the car in neutral (block the wheels and such or put on jack stands or a lift) and twist the driveshaft there shouldnt be too much play on the pinoin. some is normal, i dont know a spec, but maybe 1/8" or so. too much play is a bad sign and can mean the ring and pinion is about shot.

ring and pinion being shot is very rare on a benz even with tons of miles on them.

the only one i know of was caused by running two different size tires on the back and "working" the diff to death. and i dont know how it failed, may not have actually been the pinion.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

In my sl, I have the same problem. I think it is the old diff mounts allowing so much axel wrap that the diff rotates up and hits the under side of the car.

Friend,
We have seen worn differential side gear pinion shafts. They may be visible if you remove the level check plug and carefully examine the shafts. You will need to roll the rear wheels around to get the housing in position to see them.
All in all if that is what it is, I doubt it will ever fail tio the point of stopping the car.
Best of fortune.

Hard to tell if the flex disk is bad unless the rubber is peeling of, in which case replace pronto (new one comes with new bolts). Otherwise, if the driveshaft rotates the input shaft of the diff, but the wheels don't turn for a partial turn and it clunks, the spider carrier is worn badly. Best bet there is another diff, they aren't that bad to change and there is no other reasonable repair.

If the drive shaft turns and the pinion shaft does not, replace the flex disk pronto -- they can come apart.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Before you go changing flex discs or diffs, make sure that both the diff mount and the centre support bearing on the driveshaft are OK.

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1968 230S Automatic, Elfenbein
1975 O309D Executive Westfalia Camper Bus, Blau/ Weiss
1972 280SEL 4,5 Dunkelrot
1966 VW Type 34 "Grosser" Karmann-Ghia
1963 VW 1500 Variant Pearlweiss
1969 VW Variant Automatic, Perugruen
1971 VW Squareback Automatic, Clementine Orange
2001 E320 4Matic Wagon- Our belated welcome to the 21st century! Polar White
1973 280SEL 4,5 Sliding Roof "The Bomb", Dunkelblau.

I know it is not the center support bearing - replaced it a few years ago. The noise looks like it could be a bad rear diff mount - but I'm not sure. Any way to test, or do you replace and hope??

ryan

I'll check out the flex disk again and try to turn the driveshaft, but the disk itself looks brand new.

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Another vote for rear diff mount. I had a clunk from the rear of my 108 for years -- removed the diff mount and it was in two pieces.