Carlos I do this stuff myself so I only have one person to be pissed with should it get done wrong. I rarely miss.

If you have access to a hoist you can do this. It is not particularly difficult work. Take your time. Clean up the mess that always happens.

You may have some butterflies the first time you do it.... After that easy peasy.

 

Having worked at Mercedes Benz R&D as well as Ford Powertrain engineering, I can attest that, unless a problem has presented itself, a flush is a bad idea because sediment/clutch material, which is blissfully deposited somewhere harmless inside the trans could readily be transported to an orifice or other location causing a stroke leading to issues.

Along with that, either change trans fluid frequently - or not at all.

Frequent changes allow little degradation of the fluid. High mileage transfusions invite damage on two fronts —1: fresh fluid detergents disrupt deposits and again create the risk of stroke with transmission orifices and 2: fresh fluid has a lower dynamic friction coefficient that old fluid which invites increased slip times during shifts (not trans slip per se, but the work an already worn clutch facing and pressure plate pack has to do suddenly increases due to more slippery new fluid). Old fluid has a much “stickier” dynamic friction coefficient which reduces slip times during trans element holding and braking events.

Now if the fluid is burnt - change it and see what caused the fluid breakdown before something big breaks inside!

BillWoeb

 

Is this not a reason/Rational to change the fluid more often than required ??

Substantiating what I just said.

So, if you just want the car to last till the warrantee is up, do nothing.
But, if you want to car to get to 300,000 miles, do it regularly.

 

^^^exactly. Regular fluid changes (30k miles) and NO flush = long life.

Also, a name-brand trans tune for slightly firmer shifts (less slippage) is a big help!

I was trying to be in violent agreement with you but it didn’t read that way! Sorry about that!

 

Agree with all this. My car is an 18 S63 with 53K miles. Tranny service was last done at 30K, and I bought the car at 36K miles. I plan to keep the car a long time, which is why I wanted to do the fluid change. And sorry if I said flush, it's just a fluid and filter exchange. I can't imagine changing it more frequently than 30K miles on a sealed system. I also performed the rear diff fluid exchange last month and will do again in 25-30K miles.

 

Awesome post. Thanks.

Mercedes also specifies a time period to change the fluid. Not sure what it is for the 9G, but on the 7G+ it is seven years.

 

Modern transmissions monitor how shifting goes and change adaptations. If concerned... clear adaptations and it will figure out fresh fluid shifting quickly.

“Flushes” in the days of old generally included using a machine that connected to cooler lines. The machine measured quantity of old fluid coming out and pumped same quantity of fresh fluid in via the return line. Machine equipped with a sight glass to watch color of fluid. As it changed from brown to pink the flush was done.

MB has us dumping contents of the pan and replacing the filter(s). Older models have a drain plug in the torque converter so all that fluid is replaced as well.

40 years in auto repair here.... the only transmissions that failed with a service or flush already had a problem or were a CVT that lets be honest... are always a problem or that got filled with incorrect fluid. CVTs don’t work when fed ATF. Too often CVTs don’t work after a drain/fill with the correct fluid.

A transmission service is regular maintenance. A transmission that slips, is slow to go into gear, noisy ect has a problem that requires repairs.

I have seen fairly dramatic improvements in shift quality via a proper transmission service. The ‘06 E-55 and 221 S-65 always had improved shifting with fresh fluid.... and I didn’t leave it in the box long enough to smell or turn color.

My 222 S-65 uses the blue fluid. I change it every 30,000 miles or so. It comes out looking and smelling much better than the pink fluid in previous cars. I don’t notice changes in shift quality after a service as was the case with the older cars.

Edit: Don’t add snake oil to the transmission. If MB thought that was a good idea it would be an ingredient in the prescribed ATF.

 

I think every 30K mile fluid/filter change is a good plan: https://www.jalopnik.com/2063005/why...sion-dipstick/