StephenK

After talking to Renntech and my Mercedes dealer, I am still a little apprehensive. Renntech says you would have to be an idiot to damage the car as a result of the upgrade, and I wonder since we all have a different opinion of who is an idiot, what you would have to do to damage the car. My Mercedes dealer has said they have seen several people with problems and that they had problems with their warranties too.

Thru my talks with both of them I heard about possible problems with the transmission and Renntech mentioned possibly breaking an axle.

How likely is this and what would it take to do it?

vraa

Stephen, the SL600 already has a very powerful axle as does the SL55 to handle the strain from the immensely powerful engine. It's the 500 that doesn't have a beefed up axle. Unless you are being reckless you won't break the axle, it's a very very sturdy compenent made to handle a lot of stress.

Your Mercedes dealer will always try to squirm their way out of everything possible. I wouldn't really listen to their words like the faith of god. However, they will be the ones working on the car if something does go wrong. Know this, they can't deny work, if the failure is totally irrelavent. Such as, if your windows stop working, they can't blame it on the new ECU. Stuff like that. If you get new wheels, and your suspension fails, then they can deny work, because the wheels might not have been in OE spec. Catch the drift?

I think you are not being apprehensive, but smart. Lots of folks jump fast into modding their cars with who knows what components and then have the nerve to complain about them.

StephenK

How about the transmission, how can this mess that up???????

vraa

It won't.
There are beefed up parts however in the SL65, but it's the same 5s, so you can tell the 5sp is insanely strong.

Trimmer2

Torque, torque, torque. The new transmission computer helps manage the torque and I believe it's 65 computer. It changes shift points and etc... True, the 600 and 55 have the same steel transmission as opposed to the 500's aluminum. The brakes on both the 55 and 600 are also the same among other areas.

lorinserbenz

I wouldnt mention anything to your dealer. If you blow anything up just ship the ECU back to Renntech and have them reflash it to stock.
You would have to try REALLY hard to damage your car.
I know several people that did Renntech upgrades and have never had any issues.
I was going to to a Supercharger with Renntech or Kleeman but opted not to since I dont think my 7 speed tranny can take it. Afterall the 55 and the 600 use the 5 speed so that tells my the 7 can take it.

sillydriver

I was once speaking with the head of service at a Mercedes dealer (not the one where I take the car) who told me to go ahead with the mods, since their equipment couldn’t see the software change anyway. Just to be sure, I figured I’d take Lorinserbenz’s approach and have Renntech temporarily reflash the computers to stock if I ever suffered driveline damage. However, I very much doubt the driveline will break because it hasn’t for members like Treynor, who have brutalized their cars (his being an S600 with the same transmission as the SL) with multiple dragstrip runs using high-RPM launches.

StephenK

Do I understand this correctly that for the SL600 all of Renntechs modifications are software related and if I decide for any reason I don't like it, it can simply be changed back and all I am out is the $6,400 for the cost of the upgrade?????

Trimmer2

They can do MUCH more than sofware upgrades but, for $6400 you get the ECU Software upgrade and a new Transmission Computer. I believe the transmission computer is the AMG SL65 Computer though and is a physical box replaced near the glove box and can EASILY be changed back. I believe RennTech keeps the old computer and modifies it to the AMG 65 program to be used in future upgrades but, I could be mistaken on that one.

Just do it. It's a great bang for the buck and if you don't, you'll always be wondering what it would have been like ...and yes, it's easy to revert back to stock but, I'm sure you won't In fact, some magazines and so called experts still consider a car after ECU mods to be stock since nothing mechanical was done to the engine.

sillydriver

When I did mine I stuck a return address sticker on the transmission unit. It was still there, so in my case I think they flashed the same physical box. Hence the mod was entirely software and reversible. I also added a Brabus exhaust to the car, but that’s a separate story. I agree with Trimmer2: the software is worthwhile.

RadSteve

NOOOOOO! RennTech will modify back and forth as many times as required at no additional charge aside from shipping.