Author Topic: New 6.9 rear suspension spheres and other work  (Read 578 times)

adamb

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New 6.9 rear suspension spheres and other work
« on: 23 February 2020, 02:19 PM »
Today I replaced the rear suspension spheres on the 6.9. One had burst resulting in a very bouncy ride over the awful roads in London (and the UK in general). The last time I changed all spheres was back in 2006 or 2007. Many miles under the belt since. Interestingly the new ones don't come with red (front) or green/blue (rear) colour markings.

While I'm under there I will also be replacing the rubber donut between the propshaft and the diff. The spheres and donut with bolts are supplied by https://www.niemoeller.de/en. The diff back seal is leaking. I will need to to reseal the back cover and refresh the oil. When I rebuilt the diff back in 2002/3 I used Castrol B737 oil for ZF Limited Slip diffs. I still have a full can knocking about somewhere. It's so good to hoad :)

Also the fuel pump needs replacing and of course the filter, and any old half rotten fuel hoses. The pump works great in winter but in the summer when it gets hot the whine gets very loud. I'm afraid it'll fail on me one day soon so best act now.

Otherwise Mohan is in great shape. A joy to drive each time we go out. Not bad at all for a 43 year old.

adamb

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Re: New 6.9 rear suspension spheres and other work
« Reply #1 on: 23 February 2020, 02:20 PM »
Here are some pictures of the donut, the fuel pump assembly (dirty!) and the diff (filthy and fuzzy!)


daantjie

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Re: New 6.9 rear suspension spheres and other work
« Reply #2 on: 23 February 2020, 03:45 PM »
Might want to take a look at the high pressure hoses on your struts as well.  If they are original to the car then for sure they need to be flipped out.
Daniel
1977 450 SEL 6.9 - Astralsilber

rumb

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Re: New 6.9 rear suspension spheres and other work
« Reply #3 on: 24 February 2020, 07:30 AM »
Looks like great preparation for more driving later on. Note that the front and rear spheres are different whether marked or not.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Punker

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Re: New 6.9 rear suspension spheres and other work
« Reply #4 on: 24 February 2020, 12:50 PM »
I did the same things on my 6.9. On the fuel package I think it is very important to replace all tubes; they were in a really bad shape on my 6.9, almost dangerous. Good work. Have fun.
Björn
1978 Mercedes 6.9 # 4616 - black/black leather
BMW R 25/3

adamb

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Re: New 6.9 rear suspension spheres and other work
« Reply #5 on: 24 February 2020, 03:00 PM »
Good point regarding replacement of hydraulic hoses. I'll look into it. I had the main hose from the pump to reservoir remade at a hydraulics shop for a mere £25. Saved a tidy amount over Mercedes prices. I'd imagine the same is possible with the high pressure hoses or is it worth replacing with originals?

For the propshaft bush or donut as I call it, can anybody please confirm the direction that bolts should go in? I alternated them in the way you see in the picture but not sure that was correct. I couldn't remember how they were prior to disassembly back in the day.

I expect to change all rubber fuel hoses. I imagine they are all 43 years old. Regarding the fuel pump - here saving money makes no sense as I expect the replacement to last well into the years that buying 95/98 octane petrol becomes a relative rarity.

daantjie

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Re: New 6.9 rear suspension spheres and other work
« Reply #6 on: 24 February 2020, 03:18 PM »
For the flex disk, the nuts go at the diff/trans end from memory, however not 100% sure to be honest. Lots of posts online on other forums too, like W126 peachparts as well as Benzworld, as the methodology is the same across many models 116 126 107 etc. Make sure you place the washers correctly, there is only 1 right way to do this.  Wherever you have a "raised" section, you do not place a washer underneath the bolt head or nut.  Washers only go against the "flush" portion, if that makes sense.

For the hoses, these are pretty specifically specced hoses, and to my knowledge NLA from Benz. I think member "tcj" sells NOS ones.  As long as you match the inside diametre and pressure spec you "should" be fine to have these fabbed up, though they carry some pretty heavy pressure so you really need to be sure of what the hose can do.
Daniel
1977 450 SEL 6.9 - Astralsilber

Jed

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Re: New 6.9 rear suspension spheres and other work
« Reply #7 on: 24 February 2020, 04:24 PM »
the hydraulic hoses are available as a rebuild kit from 'uncle kent' as well.
https://mercedessource.com/store/self-leveling-suspension-sls-high-pressure-hose-replacement-kit-w-instructions


1979 Mercedes 6.9 #5206 - restored
1979 Mercedes 6.9 #6424 - ongoing restoration
1976 Mercedes 6.9 #484 - restoration?

gavin116

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Re: New 6.9 rear suspension spheres and other work
« Reply #8 on: 24 February 2020, 11:31 PM »
Hi Adam
Great to see Mohan gets year round use. Pity Mrs White live 60 miles from me...


Attached I have a picture of my flex discs for reference.

Randys01

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Re: New 6.9 rear suspension spheres and other work
« Reply #9 on: 25 February 2020, 12:39 AM »
Wow!.   how clean is that under carriage?! Note the alloy trailing arms................cast steel on the 6.9 which defies the laws of sprung versus unsprung weight!!...curious as to the weight difference.
This issue arose in another debate/thread about converting 6.9 hydra to coil springs and shockers.

daantjie

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Re: New 6.9 rear suspension spheres and other work
« Reply #10 on: 25 February 2020, 08:23 AM »
Indeed, a picture paints a thousands words, as they say, and it confirms what I said, just a lot better to see a pic ;)
Daniel
1977 450 SEL 6.9 - Astralsilber

revilla

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Re: New 6.9 rear suspension spheres and other work
« Reply #11 on: 25 February 2020, 12:07 PM »
Hi Adam
Great to see Mohan gets year round use. Pity Mrs White live 60 miles from me...


Attached I have a picture of my flex discs for reference.

That's indeed a clean car... a pleasure to admire... looks rather a picture of a new car at the dealership in 70's... well done
Robert
W116 1977 280SEL & 1979 280SE

rumb

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Re: New 6.9 rear suspension spheres and other work
« Reply #12 on: 25 February 2020, 12:18 PM »
Wow!.   how clean is that under carriage?! Note the alloy trailing arms................cast steel on the 6.9 which defies the laws of sprung versus unsprung weight!!...curious as to the weight difference.
This issue arose in another debate/thread about converting 6.9 hydra to coil springs and shockers.


6.9 are Aluminum painted black.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Randys01

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Re: New 6.9 rear suspension spheres and other work
« Reply #13 on: 25 February 2020, 02:58 PM »
Well I'll be battered on both sides. :-[ I have been under the long held [mis] understanding that the 6.9 trailing arms were steel to handle the extra torque. I have read this more than once in my travels so it's not my fabrication.
I've not had need to work on the rear end [yet ] so never had the opportunity to corroborate this matter.
I will be under that car the moment I get it back from storage!

I've never had occasion to doubt there was a difference.  When we see other 6.9 bits beefed up but not necessarily well documented it sort of made sense that the arms were beefed up too. Classic example is the front suspension upper control link which is steel over alloy.
huh!


adamb

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Re: New 6.9 rear suspension spheres and other work
« Reply #14 on: 25 February 2020, 03:25 PM »
The trailing arms on Gavin's 450 look like the same kind as mine. Not sure if they are silver or not as the car does indeed get used in varied weather. I can't vouch for the metal they are made from but given the absence of corrosion I'd speculate aluminium.

Not sure I'd want to drive Gavin's car on dirty roads. The underside doesn't stay that pristine for long.

I'll be looking for parts in Europe and the UK.  Thanks for Mercedesource recommendation but it's too far out.