I highly doubt it's slipping- our programmers are increasing line pressure as much as they can, which would have the opposite effect- it is less likely to slip. You can have your dealer pull the adaptation data for the EGS controller which will tell them if it's slipping or not.




No gearbox leaks? It's very common for the connector sleeve on the gearbox to leak past the O-rings, even on lower mileage cars.




100% sure fluid level is correct?

Fluid level requires a special dipstick from the dealer- these cars don't come with gearbox dipsticks from the factory, unfortunately. I'd also have your gearbox checked for leaks from the underside- often times that connector will leak, but the splash-pan will catch the oil (often times it's a VERY slow leak) and you'll never see a spot on your garage floor. It's a very common problem on 5-speed cars- there was even a TSB issued for that exact problem. I recently replaced one in a 2003 SL55 that has only 15K miles on it.



It's odd that it's intermittent- usually, when a tune file causes a problem, it will happen all the time and will be easy to consistently duplicate. The hotter a gearbox gets, the more sensitive it is to fluid level being correct, and since we're increasing line pressure, it only exacerbates the sensitivity, which might be why you're feeling it now, and didn't before the EGS tune.




If you have access to a factory DAS machine, I'd recommend reading out adaptation data- that will for sure tell you if it's slipping or not, and I'd also get under there and closely inspect the electrical connector going to the gearbox- if it's wet, even just a little bit, you'll need a new connector and the fluid level checked/topped off. They can also check the condition of the gearbox oil as well- if it's dark red, or burnt smelling, it's definitely time to change the fluid/filter.