S124 diff seals

[spock505]

I pretty much know the answer to this question but on the off chance someone has a workaround..

One or both of the diff axle oil seals has split, I say split as it went from nothing to dripping along with a large area sprayed under the fuel tank

Is there a way to replace without pulling the axle shafts?

Thanks

[Sugar Bear]

Axle seals require axle removal. Front of differential/pinion requires driveshaft removal. The leak could be either. Check the breather tube on the differential ( I think it has one), it could be clogged causing pressure to build up.

Good luck !!!

[RhodeIslandRed]

Originally Posted by spock505

I pretty much know the answer to this question but on the off chance someone has a workaround..

One or both of the diff axle oil seals has split, I say split as it went from nothing to dripping along with a large area sprayed under the fuel tank

Is there a way to replace without pulling the axle shafts?

Thanks

On 124 vehicles as well as 129 and 201 cars not only will you need to remove the axles but you will need to remove the differential from the vehicle and then remove its rear cover to allow the flanged stubs to be disconnected and removed in order to allow the old seal to be removed and the new seals installed. Then the flanged stubs are reinstalled, the clips securing them reinstalled and then the rear cover rebolted and secured before reinstalling the entire differential into the rear subframe.

Might as well R&R the differential mounts and the driveshaft guibo if it needs replacement while you have everything apart.

Unplug the diff ABS sensor under the rear seat rather than trying to remove the sensor itself from the diff. Plan ahead and use precautions when removing the differential front mounts Allen head bolt, stripping it will just be another headache you don't need.

you will need to either drop or lower the rear of the exhaust to get at things, if you're careful to not allow the axles themselves to over extend by hanging you can avoid removing the wheel ends of the axle from the wheel carrier. If you end up needing to completely remove the axles you'll need to get a 12 point 30 mm socket for the axle nut, and figure out a way to brace the wheel hub to remove the nut. Heating the nut before trying to remove it will help soften up the blue threadlock on it. If you don't have an impact gun you would be advised to with a hammer and punch or chisel un-stake the axle nut's deformable flange from the cut in the axle splined
end before trying to remove it.

Original axle to flanged stub fasteners are XZN 10 mm later fasteners use external/male TORX not sure of the exact size though. I've always found removing the axle to flanged stub fasteners it is easier using a long extension 24" from outside the wheel carrier to work on them. Clean the bolt heads well with a pick and brake cleaner and make sure to keep the tool straight and square to avoid stripping the head. You can brace the wheel hub with an iron bar laced between the lug studs to prevent anything rotating during the process. You can do this part quicker if you have an impact tool, I use an electric one and it works fine for this.

Good luck.

[Maxbumpo]

Could the leak be from the axle boots? Those usually crack and fail long before differential seals fail.

[spock505]

Thanks for the replies all, v helpful.

Axle boots should still be okay from overhaul 18 months ago. When fitting these I remembered seeing a video of 'split' boots which didn't require removal of stub - thought there maybe something similar with the diff/axle seals, although the split boots seem a bit of a bodge really.

RhodeIslandRed, thanks, okay with diff removal as swapped back and forth with a spare before realising it was wheel bearings rumbling away, that tuned out to be a whole other story (just ask Stretch, lol).

Having looked at diff overhauls before (including Stretch's 190 diff), the torque thing is beyond my skill level, will this need doing if I pop the axles as posted?

[spock505]

Popped out to take a few pics as worried it might be the front prop seal, apols for poor pics but 11pm here in UK.

From the photos it does appear to be one or both axle seals, any thoughts?

[RhodeIslandRed]

Originally Posted by spock505

Thanks for the replies all, v helpful.

Axle boots should still be okay from overhaul 18 months ago. When fitting these I remembered seeing a video of 'split' boots which didn't require removal of stub - thought there maybe something similar with the diff/axle seals, although the split boots seem a bit of a bodge really.

RhodeIslandRed, thanks, okay with diff removal as swapped back and forth with a spare before realising it was wheel bearings rumbling away, that tuned out to be a whole other story (just ask Stretch, lol).

Having looked at diff overhauls before (including Stretch's 190 diff), the torque thing is beyond my skill level, will this need doing if I pop the axles as posted?

If you don't need to do the input shaft seal then you would not need to do any of the preset torque routine it requires. If you unnecessarily swapped the diff already maybe you can reseal one while the other is still in use. You'll be the expert at the R&R procedure when you're done!

[spock505]

Originally Posted by RhodeIslandRed

If you don't need to do the input shaft seal then you would not need to do any of the preset torque routine it requires. If you unnecessarily swapped the diff already maybe you can reseal one while the other is still in use. You'll be the expert at the R&R procedure when you're done!

Cheers Red, yes, of course the torquing relates to input shaft, shims and so on.

It's been in and out half doz times, all new bolts and couplings so should be okay to remove easily.

This will make folks laugh, had the spare diff which was a peach, from a low milage car but sat in my garage looking heavy - ebay here we come, checked mine for leaks about a month ago before listing, sold quickly to another MB enthusiast all good.

..four weeks later ...

Last question, how easy is it to remove the inner cir clip holding axle stubs, can't see anything mention on forums (no 40 on pic) - ta

[Maxbumpo]

On a 123 diff, that clip is not bad at all. I don't see why it would be any different on your car. I think I grabbed the tab with a pliers or vice grips and a sharp yank pulled it right off.

[spock505]

Cheers Max,

[RhodeIslandRed]

isn't that the way it often turns out? At least yuo monetized it rather than taking a loss on it!

The clip comes out pretty easy as Max notes, putting it back into place a pair of long nosed pliers works well angled tip ones are a bit easier. getting the clip off and out can be done easily with a MB cluster removal hook! I'd be mindful that there might be a shim or two I seem to recall that on 123/126 diffs but there might be ones involved in these 124 diffs possibly.

Originally Posted by spock505

Cheers Red, yes, of course the torquing relates to input shaft, shims and so on.

It's been in and out half doz times, all new bolts and couplings so should be okay to remove easily.

This will make folks laugh, had the spare diff which was a peach, from a low milage car but sat in my garage looking heavy - ebay here we come, checked mine for leaks about a month ago before listing, sold quickly to another MB enthusiast all good.

..four weeks later ...

Last question, how easy is it to remove the inner cir clip holding axle stubs, can't see anything mention on forums (no 40 on pic) - ta

[jay_bob]

Note that on EPC, if the part callout is shaded, then it is not present on the vehicle whose VIN you have input into EPC.

MB documentation is nothing short of amazing.

[spock505]

Cheers for the tips,

EPC picture above was from a quick ebay search for seals, the one below is actually mine although EPC is showing 'no call out' option for part numbers.

This is not a problem as local MB dealer should be able to get the correct part numbers.

[spock505]

Went out this morning to top up diff until seals arrive, also looking closer to see which seals had failed.

Very hard due to amount of oil everywhere, fuel tank to rear was soaked.



Pictures of three seals (inconclusive)







The next part caught me totally by surprise.

Given the amount of oil everywhere I was thinking how lucky not to damage the differential permanently (especially after yesterdays road trip which couldn't be postponed).

Armed with a bottle of EP90 I started to remove the fill plug, Bosch (or words to that effect) oil gushes out, maybe half to one litre, hard to tell.



The diff only holds 1.1 litres so what's happened here, it was filled with new oil using the same ramps last year, topped off until overflowed then plug re-fitted - in theory it should be impossible to overfill?

Oil used



My thoughts turned to an earlier post regarding the vent, it's tricky to access unless I can go in through the top (remove carpet and bungs if fitted?)



The car is cool having sat overnight, it didn't splurt out as if under pressure more as though just overfilled.

Cheers

[spock505]

After a short 20 mile drive all is well, no leaks, no adverse noise.

Pondering on likely scenarios for the cause, only one springs to mind, both the diff and new oil were cold when filling.

It's always a challenge getting the bottle tube over exhaust at correct angle, then a good squeeze to get the stuff in there.

At the first signs of overflow i tend to replace the plug pronto, believing more is better, but [perhaps not.