I changed the oil and filter on my Jan 1997 C-180 5 speed electronic gearbox at the weekend and as expected the filter which fits between the sump and the bottom of the box had never been changed before. It was date stamped 8/96. Before my time with the car MB had changed the oil but clearly couldn't be bothered to drop the sump!
When the sump is dropped (be careful doing this as there is around a half litre in the sump even after removing the plug) there is a date of manufacture inside the box. Mine was made in November 96 and is number 211811. I had read that on these early 722.6 boxes one of the main bearings was bronze and can start to break up however taking the filter apart (its a small flat type nothing like an oil filter) and using a loupe I couldn't find any silver or bronze particles. In fact, despite being 8 years old and have 100000 miles it was like new. There was no sludge at the bottom of the pan only a small amount of black particles from the clutch plates.
Interestingly the filter is perhaps not designed to collect the material from the clutch pack which is what must turn the oil red to dark brown but only any metal particles. If the filter was of finer gauge I think it would get blocked with the clutch particles at higher mileage as the filter is so small.
I can see why ZF and Mercedes who make electronic boxes say these boxes are filled for life because they don't have the small passage ways that hydraulic boxes do so a calculation must have been done that the synthetic oil will still have enough lubrication properties right up until the clutch friction material wears out and a recon box is needed.See http://auto.howstuffworks.com/automatic-transmission.htm for a detailed explanation of how automatic gearboxes and torque convertors function). However even though the oil was good in my box I did notice an improvement with new oil which rather undermines what Mercedes say. A slight further improvement occurs if you reset the adaptive memory of the boxes ECU by disconnecting the car battery.
By doing a bit of digging on the internet I'm sure the special MB gearoil is in fact Esso ATF LT 71141. This a special synthetic oil made for electronic boxes and is used by ZF in BMW's etc.The spec is the same.
One last thing reading these forums and the American versions, one might imagine MB boxes go wrong more than other makes.NOT TRUE, I looked at the claim figures on the warrantydirect site(possibly warrantywise I can't remember) and in any one year of those people making claims only 3% of those claims where for gearbox problems. In other words less than 1% of boxes of those insured needed work. Given that things like errant MAF readings can give erratic gearchanging, back street garages using wrong dextron II which gives bad changes and boy racer trashing the true figure is probably even smaller for properly used and cared for boxes. The Lexus failure rate was also around 3 %.. No one makes a better automatic box than Mercedes :bannana:
adam
When the sump is dropped (be careful doing this as there is around a half litre in the sump even after removing the plug) there is a date of manufacture inside the box. Mine was made in November 96 and is number 211811. I had read that on these early 722.6 boxes one of the main bearings was bronze and can start to break up however taking the filter apart (its a small flat type nothing like an oil filter) and using a loupe I couldn't find any silver or bronze particles. In fact, despite being 8 years old and have 100000 miles it was like new. There was no sludge at the bottom of the pan only a small amount of black particles from the clutch plates.
Interestingly the filter is perhaps not designed to collect the material from the clutch pack which is what must turn the oil red to dark brown but only any metal particles. If the filter was of finer gauge I think it would get blocked with the clutch particles at higher mileage as the filter is so small.
I can see why ZF and Mercedes who make electronic boxes say these boxes are filled for life because they don't have the small passage ways that hydraulic boxes do so a calculation must have been done that the synthetic oil will still have enough lubrication properties right up until the clutch friction material wears out and a recon box is needed.See http://auto.howstuffworks.com/automatic-transmission.htm for a detailed explanation of how automatic gearboxes and torque convertors function). However even though the oil was good in my box I did notice an improvement with new oil which rather undermines what Mercedes say. A slight further improvement occurs if you reset the adaptive memory of the boxes ECU by disconnecting the car battery.
By doing a bit of digging on the internet I'm sure the special MB gearoil is in fact Esso ATF LT 71141. This a special synthetic oil made for electronic boxes and is used by ZF in BMW's etc.The spec is the same.
One last thing reading these forums and the American versions, one might imagine MB boxes go wrong more than other makes.NOT TRUE, I looked at the claim figures on the warrantydirect site(possibly warrantywise I can't remember) and in any one year of those people making claims only 3% of those claims where for gearbox problems. In other words less than 1% of boxes of those insured needed work. Given that things like errant MAF readings can give erratic gearchanging, back street garages using wrong dextron II which gives bad changes and boy racer trashing the true figure is probably even smaller for properly used and cared for boxes. The Lexus failure rate was also around 3 %.. No one makes a better automatic box than Mercedes :bannana:
adam
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and of course looking at the sump deposits is a very good guide to potential problems.
