When I first bought the CLK back in 2017, I knew the rear end was going to be the weak link. As luck would have it, I found a guy who was selling exactly what I would eventually need in order to make the back half of the car bulletproof.
Coming from the W211 platform with my E55, I didn’t know much about the 208 chassis, other than it holds great potential because it accepts the legendary M113 engine and it starts out weighing about half a ton less than the E55. I hadn’t even taken delivery of the CLK yet and I was already researching the W208 platform, figuring out where the weak links would be once I decided to put down some respectable power. In reading through lots of old posts on MBWorld, it became apparent that I would be snapping axles and grenading differentials if I didn’t beef up the rear end. Luckily I’m following in the footsteps of giants who came before me – specifically Ahmad (Blackbenzz) and Alex (2Precise).
Those two guys figured out how to mount a Mopar SRT8 differential, with its larger, stronger 215mm ring gear, into the CLK subframe, along with heavy duty Driveshaft Shop axles, rated to 1000 hp. Ahmad currently holds the 1/4 mile record for the CLK with his pass of 9.65s @ 146 mph. Alex is upgrading to a full tube chassis, and just happened to be selling his rear end setup when I was doing my research. I went ahead and bought it from him, even though I knew it would sit in a crate in my garage for over a year. I have finished Phase II of my build (weight reduction), so the time has finally come to put that sucker in!
The giant box sitting in my garage like an unopened Christmas present contains a complete rear subframe with many upgrades. The differential is out of a SRT8 (Charger, I think) and it contains a heavy-duty Quaife limited slip diff and Richmond 3.55:1 gears. The axles are from the Driveshaft Shop, and are rated to 1000 hp. The toe and camber arms are on heim joints and are completely adjustable. The other front arms are custom boxed units, which are much stronger than the flimsy factory ones. The diff is mounted on solid aluminum bushings fore and aft. The only thing left to be upgraded are the four main bushings that mount the frame to the body.
Installation was pretty simple. It was just a matter of dropping the muffler, disconnecting the driveshaft, shocks, sway bar, brake lines, and cables, then removing the four bolts that hold the subframe in. The whole thing lowered balanced on my floor jack.
The most difficult part of installing the new one was deconstructing the crate from around the rear end while it was balanced on my jack. Then I just jacked it up into place and put everything back in the reverse order.
I finished it off by installing new CLK320 rotors to save another few pounds of rotating mass.
Once I got the car back on the road, I made it to a Late Night Drags event at Portland International Raceway to get in a few test passes. My first impression is “Damn that thing is loud!” With the Richmond gears, which are known to be noisy, no rear seat or sound deadening material, and solid diff mounts, the whine from the gears is very noticeable. I’m still fighting a 3-4 shift issue, so my 1/4 mile ET did not improve with the gears, but I was able to lower my best 60′ time by about a tenth of a second from my previous best. I hope to do some more testing soon so we’ll see how well the new gears wake up the car on the low end.
Thank you for all of the other info you’ve provided. Do you know who supplies the offset rear bushings for the differential? I saw that one person on MBWorld used to make a kit, but it would appear he is no longer in the community.
I know this is old. You are using the 215mm rear end, but the back cover uses the ‘smaller’ rear mounting bolt pattern, and not the dog-leg version that seems like most of the SRT8 (and 55-series) cars used. What did that rear cover come from? I have a M113K in a Chrysler Crossfire (R170/193 chassis), and want to move to the 215, but the rear end I have will require heavy subframe mods to accommodate that dogleg rear mounting pattern.
I”m not 100% sure, because I bought the entire rear subframe already assembled from someone else. But, it looks like the rear cover came off a W211 E55. They do not have that dogleg like most of the others with the 215mm rear.
That is encouraging news! Can I ask a big favor? I have a really good 215 differential here, but it has the dogleg cover. Can you look through your pictures, and see if you have one that might have the MB part number on that rear cover? There are several different ones in the parts catalogs, and I want to get one that I am at least reasonably sure will work. Thanks!
Unfortunately I don’t have any detailed pictures of this rear end. I bought the whole thing assembled and just threw it in the car. With the diff installed, I don’t see any way to see the part number on the rear cover. I do have a link to the MBWorld thread that discussed the build of this particular setup: https://mbworld.org/forums/clk55-amg-clk63-amg-w208-w209/464573-215-diff-conversion-kit.html Maybe there is something useful in there.
Joe! Great info again! Keep up the posts on the W208!