Fluids replacement interval for maximum car life (more specifically manual gearbox/diff)

[OM605]

While it's true that you should pay attention to ALL fluids, not just change the engine oil and forget about the rest, i don't really know how often should i replace the other fluids. After buying the car with 130k km on the clock, i changed all the fluids (gearbox, giff, PS, brakes/clutch and coolant). I am pretty sure that except for the brake cicruit, all fluids were original from the factory.

Going back to the 70s, MB never specified a replacement interval for any of these fluids. You're just supposed to check the level every 30k km. While i don't like the idea of a lifetime fluid, i know many old MBs with very high mileages that never had their manual gearbox/rear diff oil changed including my E250 (at least 250k km without a gearbox or rear diff oil change) and everything is smooth as silk, no whining, no play, no leaks, nothing abnormal and it looks like those are never wear points. Of course, everything is original. I am only talking about manual gearboxes and rear diff, i know automatics are different beasts.

I was initially thinking about changing all these fluids every year (around 30k km) but this is way overkill. What about every three years (roughly 100k km)? For the PS circuit i just suck some with a syringe each time i do an oil change. Changing the coolant is not a hard job but the whole system has zero corrosion or deposits and after two years it still looks like the day i put it in. Is 100k km/three years about right for coolant and brake circuit? My biggest concern are the gearbox and the rear diff as i hate having to crawl under a car sitting on jack stands to change these especially to do something that could be useless.

My usage is 75% highway, 25% country roads, no short trips, no stop and go. The few times i drained gearbox and diff oils on old MBs it was a little bit milky from moisture but on one of my previous cars i wanted to drain the rear diff oil after 50k km and two years of highway driving and it was exactly like the day i put it it.

What would be your maintenance plan for my car? Especially for the manual gearbox and the rear differential? Of course i only use MB approved fluids for everything.

 

[Greasymechtech]

All my gearboxes get changed every 2-4 years or about 30k miles

Gearbox--- manual transmission, transfer case, front differential, rear differential, all automatic transmissions

I use aftermarket fluids that are equivalent to whatever OEM spec there is....

My brakes get bled every couple years.... simple 4-8 ounce out of each bleeder, with a siphon/refill of master to start

PSF ... is a simple siphon/refill once at every oil change interval

Antifreeze... drain/refill of radiator and bottle every couple years

 

[wpod]

Mercedes used to be really well built high cars.

 

[JohnnyG]

It depends a lot on the type of Mercedes you have and how it is used. Here is a list of prepaid maintenance items for a 2018 E Class, of various types and engines. Maybe this will help you decide. Nothing on here about manual gearboxes, but My best estimate that one change around 40-50,000 KM will do the trick. Maybe every 50,000 k if you want to be really diligent.
Sorry about the quality, you mau need to zoom in to read it clearly.

 

[AzFireGuy79]

While it's true that you should pay attention to ALL fluids, not just change the engine oil and forget about the rest, i don't really know how often should i replace the other fluids. After buying the car with 130k km on the clock, i changed all the fluids (gearbox, giff, PS, brakes/clutch and coolant). I am pretty sure that except for the brake cicruit, all fluids were original from the factory.

Going back to the 70s, MB never specified a replacement interval for any of these fluids. You're just supposed to check the level every 30k km. While i don't like the idea of a lifetime fluid, i know many old MBs with very high mileages that never had their manual gearbox/rear diff oil changed including my E250 (at least 250k km without a gearbox or rear diff oil change) and everything is smooth as silk, no whining, no play, no leaks, nothing abnormal and it looks like those are never wear points. Of course, everything is original. I am only talking about manual gearboxes and rear diff, i know automatics are different beasts.

I was initially thinking about changing all these fluids every year (around 30k km) but this is way overkill. What about every three years (roughly 100k km)? For the PS circuit i just suck some with a syringe each time i do an oil change. Changing the coolant is not a hard job but the whole system has zero corrosion or deposits and after two years it still looks like the day i put it in. Is 100k km/three years about right for coolant and brake circuit? My biggest concern are the gearbox and the rear diff as i hate having to crawl under a car sitting on jack stands to change these especially to do something that could be useless.

My usage is 75% highway, 25% country roads, no short trips, no stop and go. The few times i drained gearbox and diff oils on old MBs it was a little bit milky from moisture but on one of my previous cars i wanted to drain the rear diff oil after 50k km and two years of highway driving and it was exactly like the day i put it it.

What would be your maintenance plan for my car? Especially for the manual gearbox and the rear differential? Of course i only use MB approved fluids for everything.

Who says 30k miles is overkill?? There really is no such thing as over maintenance regarding transmissions and especially sealed gear boxes with low sump capacity. Most people get hung up on “synthetic” which in many cases can be better (formulations dictate). But the most important thing is fluid cleanliness and proper spec! Oil is cheap, transmissions and gear boxes are not. Power steering is also one of the most neglected systems. I think your approach is great with respect to that. Good luck

 

[slacktide_bitog]

You already did more fluid changes than most people do on any car

Most cars never have any of those fluids changed and arrive at the junkard on their factory fill. Lifetime fluid predates lifetime fluid

 

[IndyIan]

If you are not driving the car hard, like track days or climbing over the Alps every week, every 4-5 years or 100k km for a manual trans and diff seems good to me if it looks good coming out. Having a look at these systems and fluids more often is needed to check for leaks or contamination though. I'd think this would get you to 30 years with low odds of a problem. Here rust will claim a daily driver before most people ever wear out a moderately well maintained car.