Hi guys, I have a 2018 C63S PFL with 120,000 km. It has an electronic differential, and for some time now there's been a strange noise coming from the rear, like a "boo" sound and a rhythmic knocking sound. It gets louder with increasing speed. The car has always been serviced at the official dealership, and they changed the differential oil during the last service. I took it to an AMG specialist, and according to him, the problem is with the differential. The estimate is around €7,000. He says it's better to replace it with an original part and doesn't recommend repairing it. However, I've gotten a quote for repair, and the price is significantly different, less than €2,000. My question is whether a repaired differential is as safe as a new one. The price difference is substantial, but I don't want to compromise on safety. Do you know of any cases of repaired differentials? Apparently the parts won't be original, since Mercedes doesn't sell them, but they would be from the same manufacturers that make it, according to the mechanic.

 

If it's a shop that has experience rebuilding these, then I don't see why not, but it's not an easy job due to the very tight internal tolerances. It has to be done right. Others have also replaced the electronic diff with a mechanical LSD and coded out the electronic diff. Those are all options. Not really much of a safety concern. Depending on how you are driving, you may not even take advantage of the locking part of the differential. If the locking part fails, it's just an open differential.

Having said that, replacing it with an original part is not a bad recommendation. AMG has revised the differential. The latest version that's in the 2019+ C63S FL can be installed in the PFL. It has revised friction material and other improvements. Compared to the original one that was in the PFL, it no longer even needs the fluid flush after the first 3000 km. It doesn't have to be a brand new differential, either. There are used ones that came of crashed cars, so you have several options ranging from replacing it with a brand new one, replacing it with a used one, replacing it with a mechanical LSD, or rebuilding it by a competent drivetrain specialist.

 

I only beleve what i see - the diff-game is a little intransarent thing.
To much talking to much.
Let show you the parts.

In the moment you dont know what is exacly damaged ! But you have price for repair ???

Good Luck

 

Thank you so much for your reply; it's almost an honor to have someone as eminent as yourself respond to my message. The truth is, I don't know if it's a really good workshop or not; it's one of the few I've been able to find. I assume that both the new and rebuilt differentials were assembled with parts that Mercedes buys from a manufacturer. But of course, I'll always have the nagging feeling that it's not original. I don't drive recklessly anymore; I used to do some stupid things, but I don't anymore. I really wouldn't mind paying €5,000 if I had even the slightest doubt about safety. It's also worth mentioning that €5,000 isn't exactly a small amount of money. My dilemma is this: pay €7,000 and forget about it, or pay €2,000 and live with that worry?

 

Yes, I have a repair estimate of around €2000 without them having to open it up. It wouldn't be with Mercedes parts, but with parts from "top-tier" manufacturers. I'm even thinking of asking them to show me how badly the differential is broken. I don't mind having the car out of commission longer; I'm going to the dark side this week. A Tesla is coming my way, yes, a Tesla…

 

Diff repair is the best option for you as long as the place 100% knows what they're doing. No compromise in safety and if you're stock I don't recommend upgrading to anything as our cars already come with a decent street diff as it is. I'm quite experienced with these so any questions I can most likely relate to (pulled a few apart, compared them all facelift vs prefacelift, wavetrac, drexler etc) and have a 60/90 Drexler plated motorsport LSD in my car for years now.

Mechanically the main things that (can) go wrong are splines and gears which twist and begin to groan after you bump power up and hard launch over and over.

What mods have you done/power output? I'm curious what brand/sourced "parts" they'll be using if not oem or donor differential is used?

 

🧟‍♀️

60/90 ?
$$$ ?

 

My car is stock; the only thing I've added is the ASR exhaust valve actuator. I use it as my daily driver; in fact, I think I damaged the differential on one of my long trips with a heavy load. I drive it fairly normally, considering what kind of car it is, I don't think I'm pushing it too hard, but I do if I accelerate hard.
I'm not sure how to inspect the differential. The mechanic reinstalled it; should I ask him to take it apart again? The problem is, I can't really tell just by looking at it whether it's repairable or not.

 

Alright man I'll break it down for you.

First thing that's done is diff fluid inspection by getting the rear diff oil drained and checking the magnetic drain plug plus the oil itself for significant glitter, metal particles or chunks. If there's a decent amount of debris that’s pretty strong confirmation of internal wear.

Next to be 100% sure the “boo” sound actually coming from the diff (and not wheel bearings or something else) use chassis ears or a mechanic’s stethoscope on the diff housing, pinion seal area, axle tubes and wheel bearings during a road test or on a lift.

Here’s what they look like



Ask the shop for any photos or notes from when they had the diff out and whether they can properly open it and document the internals (gears, bearings, etc.) before finalising the quote.

Also, ask if they scanned it with Xentry/Star (or equivalent) and saw any diff lock codes. Do this and you can confirm it's the diff without jumping straight into a big job.

 

Haha 😂

 

Yes it cost so much over $10,000 I paid (about €7000). But also the AMG unit brand new is about the same price. Stock e-lsd is very good for standard and mild tune like (flash or stage 1) no problems 👍