[W126 Coupe] Diff repairs

[Steve Nervig]

On Aug 10, 2007, at 6:49 PM, marcus Johnson wrote:


> Hello all,

>

> I am having some diff problems in my 380 SEC.

>

> I have had a subtle whine and vibration at around 90km for a long  

> time and my mechanic has attempted to rectify this.

>

> We have had the car out on the road extensively as well as up on  

> the hoist and listened carefully while it runs. The conclusion is  

> that is definitely the diff.

>

> First step was to do the pinion (?) bearings and reset all the  

> clearances. Didn't fix it.

>

> He has taken the diff out and tried a couple of second hand units,  

> but they were also noisy. Given that most of the diffs now  

> available at the wrecking yard would have around 200,000 km on  

> them, this is not surprising.

>

> After trying to swap in a used item, he sent the diff out to a  

> local guy and had another go, making sure the backlash was set up  

> properly. Still didn't fix it. In fact, all it did was change the  

> vibration and noise to 70km/h instead of 90.

>

> Other items have been checked and repaired previously and have  

> helped but not fixed the problem.

>

> The tailshaft has been rebalanced and had new bearings / uni's. The  

> centre support bearing and rubber has been replaced. The motor  

> mounts are good. The flex discs have been done. The rubber diff  

> mount has been done. The tyres are new and the wheels have been  

> balanced.

>

> If it's under there, it's been replaced or checked.

>

> His conclusion, supported by the diff specialist is that the crown  

> wheel and pinion need to be replaced. Of course, you can't buy  

> these items in Australia or ex-Germany. The dealership says they  

> have no more supplies.

>

> However, I also contacted another local mechanic for their opinion  

> and they were surprised at the diagnosis. Their experience says  

> that the crown wheel and pinion rarely give trouble.

>

> Before I lay claim to the world's most expensive 380 SEC by  

> refitting the internals at huge expense, does anyone have any advice?

>

>

> marcus johnson

> 1985 380 SEC

> Melbourne, Australai


Probably not much help, Marcus, but I've been told that the *only*  
way to set up a MB rear differential is using the factory setup  
tools. It's the only way to get the preload on the crushwasher  
correct. Having never done it myself, I can only relate what was told  
to me by a long-time MB mechanic. Hopefully some more knowledgeable  
than I can help you.

Steve
1992 300CE Sportline