W124 differential

[Martin-Jundiaí]

Has anyone had to rebuild a w124 300E diff? Is it as tricky as the manual suggests?

Recently my car has started with a rumble whilst slowing down and I feel the bearings are worn, the car has done around 80K miles. However, further investigation proved hat the diff was almost dry! How that has happen I can only imagine the previous owner(s) were not so careful about maintainance. I bought the car 16K miles ago and was assured the oils had been changed!

Thanks, Martin

 

[television]

It depends on you engineering skills, MB axles do not have pinion bearing section that comes off, the crown wheel and pinion need to be blued to check that the mesh is central on the tooth faces.

There a few firms that still do it for around £250-£300

 

[Number_Cruncher]

>>Is it as tricky as the manual suggests?

Yes, it's incredibly easy to end up with a noisy whining expensive diff. Unless you have a very unusual and coveted rear axle ratio, I would investigate obtaining a second hand unit.

In terms of expense, the crown wheel and pinion gear pair are over £400. By the time you've added the bearings, seals, shims, collapsible spacer, and gaskets, you'll have quite a parts bill.

You'll need to be able to measure the pinion drag torque, and the crown wheel to pinion backlash, and some experience in interpreting gear contact patterns in engineer's blue is also helpful.

I'm quite experienced and bold, and wouldn't hesitate for long before stripping an MB engine or gearbox, but, I wouldn't be able to guarantee to be able to rebuild a diff for a luxury car and be sure that it would be sufficiently quiet.

 

[230K]

Hi

My advice would be spend £10 and put 1.1L of Millers fully synthetic diff oil in it and see how the noise is then. You could be surprised!!

230K

 

[turbopete]

seconded here. even try refilling and adding molyslip to the oil. it can help! as number cruncher already stated, unless you can get access to the right equipment, materials and have the confidence and knowledge to do such a job, under no circumstances would i recommend that you try to re-build the unit yourself!! id be reluctant to tackle it, and i worked as a mechanic for 14years!

 

[Martin-Jundiaí]

Thanks for the replies and the comments have been well noted!

In Brazil, there are some things which cost a fortune and one is a 'specialised' MB garage at R$150 an hour! Imagine paying 150 quid an hour! Indie MB garages tend to be a touch shady...to say the least. There are rumours about one in particular that 'finds' things wrong with the car...even when you didn't ask them to check it out and when YOU knew it was working perfectly!

Well, I'm going to look around for a second-hand unit and until then I'll flush out the diff and fill it with a slightly heavier oil (SAE 90?)and see if I can find Molyslip or the such-like.

 

[brianbrian]

I used to repair diffs 40yrs ago on elevator g/boxes its not a diy job .

 

[Martin-Jundiaí]

I've been chatting to a MB technician on the Brazilian MB forum and he claims that if it's just the bearings that are worn, it shouldn't be too complicated to swap them out. Luckily where I live most of the major bearing manufacturers have retail outlets so good quality parts are readily available. I may investigate this route too.

The line drawings available from that Russian EPC should at least give the mechanic an idea BEFORE removing the diff.

 

[Martin-Jundiaí]

After discussing this topic with the mechanic yesterday. He asked me if I could get a hold of torque specs and tolerances. It appears that the noise is coming from the from bearing, which he claims is not such a difficult job to do.

So the question is...does anyone have these settings? I'm trying to find them on other forums too.

Thanks once again, Martin

 

[Number_Cruncher]

Which bearing? - there's more than one!

 

[Martin-Jundiaí]

Sorry, the front bearing.