As many of you guys know the C55 has a good old reliable and strong 5 speed tranny, but there was the slk55 with a 7 spd and the clk550 with a 7 as well.
I want to put in a 7, but idk how much torque it can handle and i know there are MAJOR problems with the SLK55 trannys breaking and falling apart but because of a minor part... so what should I do?

 

Try to find an SLK55 transmisson and see if you can do the swap. Not sure if the ECU/TCU's will communicate with each other though. Make sure you get one that doesn't have the bad batch of valve bodies.

I guess the real question is why do you want to waste money and time to do this? Did you blow your current transmission? Good luck, it would be interesting to see.

 

If you do a search sooner or later you will find the guy that did this. He had to use STAR with developer mode to match the car to 7 speed combo, I think this was the 55K put in a Crossfire. In another instance a guy converted his CLS 550 to a 55K and just used the same 7 speed. Without any software it actually shifted through the gears but at first he thought it needed some major recalibration, after a driving it for a while he seemed to think it had adapted well enough by itself. Maybe search the CLS fourum.

 

Why would you want 7spd?
Honestly, I don't like 7 spd in my slk... But then, I don't really like the 5 spd in my C55 either...
Slowwww n unresponsive

 

you did it you could have installed an IPT 800 hp rated built 5 speed and tossed in another 100hp for it to handle with no issues. The 5 speed is capable of taking more power stock anyway.

 

Just get an SLK55.

 

rcompart is who you are freferring to. but he didnt put a 7 speed in the crossfire. it has the 722.6 trans
the cls is running the 7 speed but he is swapping to a 722.6 because the issues with the tcu and the 5 speed handles more power than the 7 speed

 

I wouldn't really bother to be honest. I hated the 7 speed in my C230 because it took way to many gear changes to do anything because of the low power of the car but I liked it better in the SLK55 I drove. Though I didn't know the 7 speed had some problem years or couldn't handle the power like a 5 speed since they use the 7 in everything now.

If you going to spend the money, just get a custom bell housing made a throw a T56 in there!

 

Unless the transmission was larger, wouldn't more gears on a transmission that was the same size be a lot weaker? I'm already scared of the stock transmission breaking when I track the car. A 6th gear on the C32 would be great though, I find the RPM's a bit high for highway cruising.

 

When the 7 speed first came out it couldn't handle the power, hence why most of the AMG's (especially the V8 S/C ones) remained with the 5 speed. The SLK55 I think was the first one to trial the 7 speed with a higher torque motor. Obviously things have changed as the design was refined.

And just because things are more compact doesn't mean they're worse/weaker. Just means more refined with better design and materials.

 

Again, I echo those who ask the question of why you want to swap the transmissions. The SLK 55's acceleration advantage over the C55 has mainly to do with significantly lower weight. Differences in shift speeds are not that significant. Even though there are 2 more gear ratios, the last 2 gears are both essentially overdrive gears for high cruising. From a performance point of view, the 7 speed essentially has only 1 more gear than the 5 speed to optimize acceleration. For our 5.4L engine, I don't think it is that important because of the relatively flat torque curve.

What is far more interesting to me would be to swap our entire engine and transmission with the CLK63's (not the black series) 6.2L engine and 7 speed transmission (ECU/TCU included). It should be a good fit, as the W209 and C55 share almost identical chassis dimensions. In essence, one gets a W203 "C63" in a much lighter package than the W204 C63.....

Anybody want to attempt???....haha.

 

lol oh man.
I didnt blow a tranny, i do a lot of driving (highway) and it would be nice to have lower RPM's without sacrificing performance, my plan is to do as much without going forced induction.
I wanted brabus to do my 5.5 to a 6.1 (I think.) If you say its slow and unresponsive then thats not good, i just want a good match, i would be happy with a 6 but for unknown reasons MB has not done this lol

 

Well, if you have a lot of budget on this project, DCT 7 spd on SL63 was just wonderful.
SLK55's 7spd tranny is a bit similar to C55... I think it shifts a really bit quicker but still it's very slow and unresponsive.
Honestly, 1, 2nd gear is useless... 7th is ok but it is very close to 6th

 

But that actor did

Seriously, drag racers for years have preferred less gears in their cars. Shift times mean higher ETs...........Way back in the 60s, they used the two speed Powerglides from GM for their one shift and bulletproof design and strength. I dont see, other than fuel economy, that the 7 speed will do much for the 55 (are you looking for performance or fuel economy). A fabricated final drive gear may do you better .......

 

My dad's C280 Avantgarde has the 7 speed auto. I can understand why it does have it. The 3.0L V6 motor is rather torqueless. The 1st gear gives it the impression that it has a lot more torque than it really does. I can actually power oversteer the car in 1st gear. The rest of the gears are quite useless in terms of acceleration. Even my dad says that the car rarely uses the 7th gear, even on the highway. It's not very useful. For both C32/C55, there is more than enough torque. Shorter gears are not required or even beneficial. I could see it actually making the car slower and shifting patterns even more complicated and annoying. More gears = better fuel economy in this case. Still, I'd always prefer a larger gearbox. Who knows if they used better materials when they made this compact gearbox? Older drag trannys in american drag cars are only 4 speed. There's a reason why they are so reliable.

Bry

 

The reliability is a big issue for me, i want to keep my car for a while (i love it to death and you would have to pry the key from my dead hands) And lesser gears have always been more reliable, my friend has a 71 camaro and only has 3 gears...its still running like a champ.
Does anyone know any place that can fabricate a gear really well?

 

I love that DCT
Happen to know how much?

 

Guaranteed that the amount of money you're going to spend to get this done and working is going to outweigh your highway rpm gas savings by tenfold, heck maybe even hundredfold. That's not counting the headache it's going to be, and if it's even going to work (or have to undo everything if it doesnt).

 

Its a pretty big risk lol
I completely forgot about the DCT, it would be nice to have if it is able to work lol

 

on a street engine allows a wide power band engine the time to best use that power band up the rev range.
The 2 speed powerglide drag engine is used for engines with a narrow power band. High torque to take off high gear for the top end.
A CVT trans would be the ultimate since it has an infinite range of combinations
That's what is coming next in the Mercedes bag of tricks.

 

The tranny in a the SL63 is a MCT not a DCT, only the SLS uses mercedes DCT.

 

I got confused.. hahah But yea.. SL63 tranny was a lot better.
I didn't get to drive my friend's SLS yet but he told me its 100000X better than SL63..

 

lol
The CVT is no good, you have severe power loss, i dont like it at all, i have on on the CX-7, its good for manual mode, but driving on the highway my C55 gets better gas mileage lol

 

I love the 7spd on my C63. Close gears and fast. Clk55s 5spd has longer gears and slower shifts.

 

Is yours a DCT?
Can you find a quote for me? That would be nice lol