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  #1  
Old 10-16-2008, 01:18 AM
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Next Issue...

My 1970 250C makes a klunking noise on acceleration.
It's coming from the rear of the car & continues up to about 40 m.p.h.
Once I get up to cruising/highway speed (above 40) the noise goes away & the car rides smoothly.
I suspect the center driveshaft support bearing.

Does anyone have any other ideas?

Also, is it dangerous to drive it like this?

Thanks!

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  #2  
Old 10-16-2008, 08:45 AM
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Location: Des Moines, WA
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It could be the bearing or the flex disks. It could also be the links for the sway bar. They use a plastic bearing and it falls out after a while.

Any of these can be dangerous. The drive shaft can come loose or a link can get caught up in moving parts.

I had Mike at Walt's Radiator check my flex disks on my 450SEL during an oil change because I had a thumping noise on acceleration. He knew exactly what I was talking about, told me the front was shot and needed replacing soon. I ordered one from Phil and Walt's put it in for $85. My mystery noise is gone.

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
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  #3  
Old 10-16-2008, 02:15 PM
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Thanks so much.

If all this winds up costing me is $85 I'll be glad to pay it!

The car is far from perfect but, after only a month of ownership, I do love it!
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  #4  
Old 10-16-2008, 08:33 PM
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Hello,

My first guess is the rubber in center driveshaft support has gone bad. This condition will cause a knocking/thumping sound under acelleration. The sound originates from between the front seats under the car.

Normally the driveshaft is removed, the rubber carrier and bearing are changed. All the flex discs should be checked at this time. Some models have two driveshaft supports and a three piece driveshaft! You'll have twice the cost in parts if this is the case since you should replace both. Always mark the drive shaft parts so they assemble exactly to prevent any balance and vibration problems.
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Joe Alexander
Blacklick, Ohio
1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)
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  #5  
Old 10-17-2008, 02:21 PM
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Quote:
Originally Posted by ja17 View Post
Hello,

My first guess is the rubber in center driveshaft support has gone bad. This condition will cause a knocking/thumping sound under acelleration. The sound originates from between the front seats under the car.
Hi,

That sounds like what's happening; it's coming from between the front seats (possibly just slightly behind them?) & definitely from the underneath of the car.

It's a rotating kind of a sound; with rythmic, repetitious "klunks" that increase and decrease with acceleration and deceleration.

Sometimes, when turning hard from a stop (as in pulling out of my driveway into traffic), it even makes a loud "POP" or two before the klunking begins.

I haven't had a chance to jack the car up & really get a good look at it yet but tomorrow I will.

Thanks for the info!

- Wil
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  #6  
Old 10-18-2008, 01:07 PM
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Originally Posted by NewWilOrder View Post
Hi,

That sounds like what's happening; it's coming from between the front seats (possibly just slightly behind them?) & definitely from the underneath of the car.

It's a rotating kind of a sound; with rythmic, repetitious "klunks" that increase and decrease with acceleration and deceleration.

Sometimes, when turning hard from a stop (as in pulling out of my driveway into traffic), it even makes a loud "POP" or two before the klunking begins.

I haven't had a chance to jack the car up & really get a good look at it yet but tomorrow I will.

Thanks for the info!

- Wil

That's what mine sounded like, although a bit more of a muted thud than a metallic clunk.

The pop sound may be coming from a rear CV joint and not the drive shaft. You might want to check out the CV joints while you are under there.

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
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  #7  
Old 10-18-2008, 03:56 PM
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Originally Posted by 250 Coupe View Post
That's what mine sounded like, although a bit more of a muted thud than a metallic clunk.

The pop sound may be coming from a rear CV joint and not the drive shaft. You might want to check out the CV joints while you are under there.

Michael
Thanks, I'll do that.

I got under the car today & the center support bearing itself seems okay but the rubber around it is DEFINITELY toast.

I don't have the ability to do the work myself so I'll be dropping it off at the mechanic on Tuesday. Any idea what this should cost?

I looked at the CV boots last week & they (along with everything else on this 38 year old car) are dried out. I think that might be something I can do myself, though.

Also, just out of curiousity, how much play should there be at the U joint itself? With the rubber around the center support bearing shot, I can move both the front & rear driveshafts ALOT but they move together.

Thanks again!

- Wil

Last edited by NewWilOrder; 10-19-2008 at 10:53 AM.
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  #8  
Old 10-19-2008, 10:33 PM
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Location: Blacklick, Ohio
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Hello,

I have been able to just remove the front driveshaft and replace the support and bearing saving a lot of time. I use a air chisel with a blunt end to drive the old assembly off the shaft while in the car after the front driveshaft is removed and the lock ring is removed. Remember to mark the driveshaft halves so they go back on exactly. I use the correct size metal or plastic tube to drive the new parts back onto the shaft. I am able to do the job in about 45 minutes. Most mechanics will remove the entire drive shaft quite a bit more work figure at least 2 hours. Also the drive shaft will have to be compressed. There is a telescoping section locked by a large nut 46mm and 42mm. You will have to loosen these to start.

The CV boots require an expensive MB tool to crimp the metal cans after the new rubber is installed. Find someone who is supplying split boots for this model. I heard they are available. You can also get re-built half shafts. Still expensive. It requires a bit of work to remove the half shafts. Lower diff, remove rear cover, remove lock rings, unfasten bolt at rear brake disc and remove the half shaft. The split boot still seems like a good idea!
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Joe Alexander
Blacklick, Ohio
1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)
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  #9  
Old 10-20-2008, 11:30 PM
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Quote:
Originally Posted by ja17 View Post
Hello,

I have been able to just remove the front driveshaft and replace the support and bearing saving a lot of time. I use a air chisel with a blunt end to drive the old assembly off the shaft while in the car after the front driveshaft is removed and the lock ring is removed. Remember to mark the driveshaft halves so they go back on exactly. I use the correct size metal or plastic tube to drive the new parts back onto the shaft. I am able to do the job in about 45 minutes. Most mechanics will remove the entire drive shaft quite a bit more work figure at least 2 hours. Also the drive shaft will have to be compressed. There is a telescoping section locked by a large nut 46mm and 42mm. You will have to loosen these to start.

The CV boots require an expensive MB tool to crimp the metal cans after the new rubber is installed. Find someone who is supplying split boots for this model. I heard they are available. You can also get re-built half shafts. Still expensive. It requires a bit of work to remove the half shafts. Lower diff, remove rear cover, remove lock rings, unfasten bolt at rear brake disc and remove the half shaft. The split boot still seems like a good idea!
Hi Joe,

It's good to have an idea of what may be involved.

Thanks for the info, it's greatly appreciated!

- Wil
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  #10  
Old 10-21-2008, 06:56 AM
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Location: brisbane,Qld.Australia
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Whilst I will normally bow down to Joes extensive knowledge ( especially regarding W113's) the situation regarding CV joints on the W107 (etc etc ) is one where split joint rubbers are NOT available and will not work on a high speed spinning axle. BUT there is an answer because dismantling those joints can only be described as bastard of a job which requires special tools .
You can get both axles rebooted (?) by anyone who has a Astoria Flex boot gun. It takes around 20-30 minutes to do each side and the boots cost under $20 each.
http://www.thetoolwarehouse.net/shop/ARA-FB5000PK.html

Using as Asotia gun there is no need to remove the axles,just undo the 13 mm bolt in the center of each rear hub and push the 1/2 shaft free. replace the boots and refit the axles and your done.
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  #11  
Old 10-21-2008, 01:19 PM
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Quote:
Originally Posted by mercmad6.3 View Post
You can get both axles rebooted (?) by anyone who has a Astoria Flex boot gun. It takes around 20-30 minutes to do each side and the boots cost under $20 each.
http://www.thetoolwarehouse.net/shop/ARA-FB5000PK.html

Using as Asotia gun there is no need to remove the axles,just undo the 13 mm bolt in the center of each rear hub and push the 1/2 shaft free. replace the boots and refit the axles and your done.
BEAUTIFUL!

Thank you so much!

- Wil

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