Stuart_Dands

Hello

I have had my 1998 Sl500 for a few months now and it is currently undergoing a what was never supposed to be but has somehow turned into a full body respray.....

I originally planned to paint both bumpers due to small cosmetic marks but that got slightly out of hand and here we are.

When it is off the road I have been doing some maintenance and improvements. I have changed the rear differential oil, along with an engine service, but I have researched and researched 'to change or not to change' the gearbox oil until I am blue in the face and I am no further forward.

Now I understand that it is supposed to be a lifetime fill but the car is now 16 years old and has done just over 100K miles which is a fair mileage on the same oil if it has never been changed! That said however the gearbox is performing very smoothly, is quick to change and very responsive, not in any way sluggish at all.

This is a job I would consider doing myself although I have read that these gearboxes are very sensitive to the correct oil levels and this is making me less enthusiastic to do this job in case of doing more harm than good.

What is the general opinion on this subject? Change it or be happy that it's performing well and forget about it?

Euro Legends

Lifetime doesn't mean lifetime... It still needs to be changed. The dealer only charges $300~ for a new trans filter gasket and fluid with a flush to remove contamination of water and any wear that has accumulated (metal) it is advised to do I believe every 60k miles. It is important to flush the system not just drain and fill to remove contamination. Just because you don't have a problem doesn't mean don't do it. It is preventative maintenance. You wouldn't drive your car 100k miles with no oil change for your engine right?

Stuart_Dands

Appreciate the reply! I have researched further and read that this gearbox can be prone to Viscosity shock if a complete fluid change is carried out rather than just the oil pan quantity. Unsure what to make of that if I am really honest as it is not something I have heard of before. But I appreciate all that you read on the internet is not always the whole truth. I have inspected the fill tube and the oil has certainly had attention of some description in the past as the Red tab has been removed from the stopper on the top of the fill tube. You're right I would not drive for 100K without an engine oil change, I barely do 3K without one on any of my cars! Thanks again for the reply.

Euro Legends

I just took a transmission and drivetrain class last semester and ask that very question from the teacher that worked as a transmission specialist I think since the 70s... His reply said it was a myth and that the only potential damage would be I think it was the torque converter because of it spinning causes all the crap to go to the outside because of spinning so by using the machine to flush the fluid you'll be stirring up the crud through the system... But when we used the machine we drained the pan then it flushed it for several mi Utes to clean out the whole system. The teacher said there isn't much to go wrong in an auto transmission... Also the way a transmission (auto) works is by fluid pressure (hydraulic) similar to the convertible top or brake system. You know what a big difference changing your break fluid makes on performance I imagine... Just information I learned so there should be no issue with doing it since it's the dealer procedure and recommended. If you have any worry pay the dealer in case anything goes wrong you'll have someone to blame and $300 isn't much compared to a new transmission... But again there should be 0 issue.

Stuart_Dands

Thanks for the heads up. Makes good sense what you say! Off to the dealer I go then!!

Euro Legends

Your welcome... Also you wouldn't save much money doing it yourself I bought the parts wholesale from the dealer and it's about the same cost as them to do the service. Sometimes it just makes sense to go to the dealer.