Finally - I've been waiting a long time to pull this off but now I have. My E63 is now running the same 3.06 final drive ratio as the SL63! Our stock rear end ratio is 2.82. Hey it could be worse...the M157 turbo guys are running 2.65!

For those of you that don't what this means, basically a bigger rear end ratio (also known as final drive ratio or pinion and ring gear ratio) will multiply more torque to the driven wheels from the engine. Bigger final drive gear means stronger acceleration at the expense of the top speed possibly in any given gear. There's a point of diminishing returns for sure (ie, too big isn't a great idea either) but a small upgrade is normally a good thing in most cars. Particularly on our cars which (typically) don't max out the top speed in fourth gear at the drag strip. This mod is sure to help more people trap higher and therefore run faster.

Anyway, enough of the explanation of how it works - for more detail, just Google it

So, here's how I did it - you can of course do it differently, but my way was (seemingly) cheaper at the time. I purchased a rear diff from a Chrysler SRT8 for £100 on eBay UK. Many Chrysler and MB parts are interchangeable and I remember from my E55 days that guys were taking gears designed for the SRT models and running them in their cars with good results. The next step was to find a guy that can perform the programming. A friend of mine is a great mechanic who knows a guy etc. It was this guy whom was able to tune my TCU (tranny ECU). The TCU tuning takes into account ramp angles, traction control, the ratio itself and other witchcraft which I don't know about. Shift points are not changed and torque limiters are the same. I was of course nervous about everything, but I've been known to take gambles before with tuning mods, so I thought what the hell. I gave the car to my friend a couple of weeks ago to start the work - the first step being to remove the TCU for tuning. Once the tuning was done, it was crunch time for the install and to see if it would work or not. With the stock AMG diff removed, my friend set about taking apart the casings. Why? My stock diff has the P30 LSD inside. The Chrysler unit didn't...I simply wanted the ring and pinion shaft from it. Some pics below, to get you up to speed at this point in the assembly:

Rear AMG diff removed




Both casings opened up. AMG on the right, Chrysler on the left



Probably hard to make out from the next two pictures, but the casing is wider on the Chrysler unit. It was a tight squeeze wiggling out the P30 LSD from it's casing






Two units side by side. Excuse the dirt n ickiness









Tranny mount was in clear view, so I decided to buy a new one. This is the original one with 95k of use (not that you can make out the use from this pic of course)




Bit irrelevant t show pics of the underside of the car, but what the hell. This is the rear end with the diff removed and propshaft flexdisc hanging




Driveshafts minus the diff



The all-important TCU








So with all of the admiration of the diffs out of the way, we set about splitting the diff units. First up was the AMG unit - these bolts are reeeeeeeally tough to crack.




And now the Chrysler unit without the ring gear




Aaaaand stumbling block. So it turns out that the propshaft flange off the diff casing is different from Chrysler to AMG (110mm vs 120mm). Undoing the big nut in itself was hard enough, but sadly the outside of the bearings which align the pinion to the casing had seized on both casings...




...which meant that I had to then put them into a box and drop them off at the local transmission shop to have the pinion shafts removed. This took a week (annoyingly) but we got there in the end.




OE




Chrysler




After the shop had done the work (new bearings installed of course), it was time to finally fit the 3.06 ring gear and LSD into the Chrysler casing which now has the AMG propshaft flange. Here are some pics of the part numbers of the ring gears - feel free to use these as a reference point. You can see the ratios stamped onto each ring gear.





That's pretty much it in terms of pics of the diffs n oily bits. The installation from there on was quite straightforward and the car was fine with the new gear set up from the get go. No adaptation reset or anything unusual needed. I picked the car up last night.

Here are some additional parts that you'll need for the installation, complete with MB part numbers. Nothing glamorous or exciting, but without these, you won't have an installation:




New tranny mount - notice the different (W212 specific) part number vs what was on the car originally...spooky













If any of you would like to go down the route of finding an SRT8 diff to steal the ring and pinion from, here is the part number:






So how does it drive?

It's nice. I haven't gone crazy with it yet, but it definitely feels as though the car has picked up what would feel like 30-40hp....it's a bit like when you went from stock to tuned + headers. I particularly love how friggin angry the thing is in 1st and 2nd with minimal throttle, hehe, it's so forceful! I gave it a bit of gas on a slight bend in first and second (dry, warm evening) and it wanted to break traction. The seat of the pants feel is there and I'm happy with it for the moment. At some point this week I'll run some stopwatch tests to work out an average as to how many tenths have been taken off acceleration times etc. WOT certainly feels pretty damn nice, I must say.


How do I do this?

You'll need the 3.06 ring and pinion, either from an old Chrysler SRT8, or from a Mercedes SL63 or SLK55 (I think). Alternatively, you can go to somewhere like Richmond Gear or another vendor that will sell you the gears. The TCU tuning is critical or you'll hit limp mode (and it's why you've not read of somebody doing this previously). Lastly, you'll need the additional service parts above like the one-time-use bolts, fluids and gasket etc. I've been asked to act n behalf of my friends shop whom did the installation if anybody else needs this done in the UK regarding the installation, TCU tune etc


How much did it cost?

The 3.06 gear was £100GBP, but I had to bend over and pay £350GBP at the tranny shop for the pinion shaft swap. So call it £450GBP for the gears, which....tbh is about what they would cost as standalone items from RIchmond Gear in the USA
The TCU tuning was the GBP equivalent of $1350 - expensive, yes.
The installation was £600GBP which given how long it took and the inconvenience of having to push my car around the workshop, was pretty good value
The service parts from MB was around £200GBP, but that includes a tranny mount which isn't strictly necessary

Grand total is (sorry, I keep mixing $ and £) approx $2300....honestly, given how much we would pay for an airbox or CF driveshaft, this is pretty damn good value. Hell, a used pair of headers before installation is around $2k. The gains will 100% be there - i'll have some figures for you all in due course. Expect your car to be on downtime for approx 3 weeks. A bit of a pain, but if you can manage and survive the long install, it will be worth it. Acceleration gains are there any any rpm and it's totally linear. I expect that road course and drag guys will particularly love this mod as it will no doubt reduce ETs.

 

Sign me up. Nice work!

 

Love it man! Great work and definitely worth it.i had a custom 3.64 rear end built for my m3 and completely changed the car.

my issue is I have zero traction in first and mostly second gear now lol.

 

 

According to the Technical data sheets I downloaded from Mercedes-Benz Canada both the 2012 C63 AMG sedan and coupe have a Final drive ratio of 3.06 from the factory. Something to consider and research before getting too deep into doing a rear axle ratio conversion to a ratio of 3.06 on a C63.

 

Good call Mort. I'll look into the part numbers.

 

 

I have a 2013 open diff sitting in my garage. I can try to turn it and see what the final drive is

 

I need this mod

 

best bet is salvage yards.i paid 800 us shipped for a limited slip out of a 2012.

my car had every option other than the limited slip.

 

Gotta love them srt8's...

I guess the daimler-chrysler partnership in a way still continues in new models...and yes, I know the details, because I know someone is gonna say it.

 

 

If i'm not mistaken;

07-13 "W204 C63", always comes with "2.82",,

"3.06" with (HAG215) comes as optional with "W209 Clk55-Dtm & R230 Sl63"..!

-;ZAYED;-

 

I had read threads in the past about the ratio on the variants of the W204 (I was researching this high and low like a mad man for nearly a near) and I had actually found an old thread from Mort stating the same thing. However, from speaking with my friend and his TCU guy, checking with that MB online thing that tells you everything about your car, I was told that all W204 models have the 2.82. What surprises me then is why would MB give the 3.06 to the 2012 models, but not the black series which is the flagship of the M156 series Besides, we would also see faster times for the facelift models and higher trap speeds on average. I would also expect those models to dyno higher due to more force being applied to the rollers via the wheels. Food for thought. BTW FWIW i'm not getting defensive or anything...just stating what I think I know.

On a more positive note, hot damn, this thing feels so strong now! First gear was already a bit of a blur on my car but now it's just pure guesswork as to when I need to pull the trigger for the upshift. It really is over in a flash and I feel like I'm holding onto dear life as it shifts into 2nd and still keeps pulling hard. I wasn't able to time anything yesterday or log my speedo, but I'm super happy with this mod. Easily the single best mod on this car I've done. I imagine that a Weistec stage 1 car won't be much different to what it feels like right now (on a W212 body, not a stage 1 W204).

A lovely and unexpected side effect is that fuel economy at DD town driving speeds has actually gone UP! It's hitting the shift points earlier and happily going into higher gears at slow commuting speeds. For example this morning I noticed that it was going into 5th before 30mph and spent most of the speed from 20-30 in 4th. Hell it's going into 7th at just over 40mph whereas before it was 45mph. As as result, I managed 18.5mpg on the way to the office this morning. My normal average is between 16.8 and 17.2-3 on a good day. The icing on the cake is that even though I was in higher gears sitting on ~1000rpm most of the time, any dab of the throttle would result in the car smoothly accelerating forward with more torque than it would have done before in a lower gear....brilliant! I guess the only downside to this is that highway economy would no doubt suffer a little too. Just as well that I don't do much highway driving then.

 

Out of curiosity, does this have any ill effects on the smoothness of downshift rev matching? I figure the ECU is pre-programmed to rev to a particular rpm based on speed and gear selection.

 

Nope, not in the slightest. It's as smooth as I can ever remember my car to be tbh.

 

After this nice swap, is it needs to tune ECU or TCU..??

-;ZAYED;-

 

I know there's parameters that can be changed in the ECU and ESP unit for the final drive ratio, but don't know of anywhere in the TCU, is this why it had to be replaced?

 

No it doesn't show on the dada card,at least not on the ones I have seen.

Here are the Technical Data Sheets from MB Canada. They may in fact not be correct but this is what they showed at the time.

 

You can pick up cheap c300 diffs on Ebay guys

 

I think the info. about final Ratio from "MB/Canada" data-sheet is incorrect..!,,

unless if they got differ spec. coding in their VIN #s..!?!

-;ZAYED;-

 

I have my original 2013 diff off the car.i can confirm that we get a 2.82 ratio in the usa.

 

Nice one Celica. Big ups for trying something out the box on your car.
Must feel great.