I never did find a comprehensive guide to setting up a new LSD in the E55's rear end. The DIY Quaife Install thread shows how to get the unit out of the car and do a simple R&R of a Quaife, but nobody ever talks about how to *properly* setup backlash and preload on the carrier.

If you've never setup one of these gearsets before you might be surprised at how the preload and backlash are set (I was, anyway). Preload is how much "squeeze" is put on the side bearings by the case, and Backlash is how much "play" there is between the ring and pinion gears. Backlash is measured the same as on pretty much any other rear-end, so I won't get into details. The preload is measured by how much the case is "stretched", or "spread" from its natural, relaxed state. Certain rear ends, like the Ford 9" use spanners that you screw in and out to adjust both the preload and the backlash. The AMG rear end in our cars has no adjusting mechanism. It's actually the thickness of the big-*** C-clips that determines both values. That means if you want to do it right, you need to have a set of machined C-clips handy (in various thicknesses) and find the right combo that gives you the necessary preload and backlash values. (You can buy them from AutoTech)

I decided to roll the dice and tear mine apart hoping that either A) the factory C-clips would work as-is with the Wavetrac, or B) they would be too *thick* and could be sanded down to spec. (Hint: It turned out to be B).

I built a home-made jig that would act as both a spreader and a jig for measuring backlash and preload.



I used two pieces of 1.5" square steel tubing, one piece of scrap aluminum U-channel, and two pieces of threaded rod (not shown in this picture). The square pieces allowed me to suspend the unit and made it easy to work on. The two threded rods go between the square tubes and use nuts and washers to push the bars apart, which will spread the case since it's bolted to the bars.



Here you can see the rods in place, and see how I measured preload. In this picture the preload was too much (.012"), so I had to take out the C-clips and sand them down by about .004" to get the desired value of .008".



In order to sand down the C-clips evenly, I got two scrap aluminum blocks, made sure they were dead flat, and used double-sided scotch tape to attach a rubber sheet to one and a piece of sandpaper to the other. I then proceeded to sand in a circular motion, checking the C-clip thickness with a vernier caliper every so often. Make sure to check at several points around the clip. It took about an hour to get it right!

Overall, this was a time-consuming job, but totally worth it.

For reference, my backlash value was .006", preload was .008", and I torqued the ring gear bolts to 103 ft-lbs. Those values were all measured on the factory unit during disassembly, and they fall in line with the metric equivalents that I have found for other models that use this same wavetrac part number.

 

Great right up. As I'm looking to tackle this job my self. Still on the fence on Quaife or Wavetrac, steering more towards Wavetrac. and maybe some gears as well 306's.

 

Macgyver is taking notes, LOL. Nice work.

 

JoeJernst I plan on tackling this project very soon. I'm planning on doing a 3.06 ring and pinion and the Wavetrac LSD. on your post with the Wavetrac it should bolt right up and use factory clip?

 

Yes and No. You *do* use MB factory clips, but you will *probably* need to fine-tune the thickness of those clips in order to get your backlash and preload within spec.

 

That's pretty bizarre if not disappointing that the method of adjustment is removing actual material.

Well done on the write up!

 

So according to your install the case is under .008" of expanding pressure from diff preload, and therefore without pre-expanding the case with setup you made technically you wouldn't be able to get the c-clips in? Is .008" the WIS spec? Did you convert this to SAE to due to your dial indicator lol? This sounds crazy to me, but I'm about to do the install so I'm all ears. I plan on just pulling the old bearings and pushing them back on the wavetrac, ordering bearings from France seems like a hassle when the old ones should be fine.

 

Yes, you are correct, but I will elaborate on how I arrived where I did.

First, I don't think the WIS has any specs on this particular differential. All I could find were other, similar units that use the same ring gear. Ultimately what matters most is that you get things back in the same way they came out, so be sure to measure YOUR preload and backlash and use those as your target values. Assuming you make a jig like mine, you will see that the overall width of the case will be about .008" LESS once you have removed a snap ring. You should get your dial indicator setup and zeroed before you have any pressure on the case. Then expand the case by a few thou so the first snapring is easy to get out. When you relax the case you should see the indicator go to about .008" on the other side of zero. Make a note of that actual number because that's what you should shoot for on reassembly.

Oh, and don't forget to measure backlash before all of that! I believe a healthy rear-end should have about .006" of backlash.

As I do not have any metric indicators, I used inches, but I'll leave it up to you to convert to mm if you so choose.

 

Preparing for the Wavetrac. This looks like it will take time...

 

Yeah, it's definitely the biggest job I've tackled on this car yet. Just getting the unit out and back into the car was a major job! Make sure you take the time to understand how it all works and you can do it!

 

Already did that part 3 times, what's another one...
If that sounds confusing or intriguing, stay tuned for more videos soon. Le sigh.

EDIT: It's a shame you're so far.

 

Feel free to PM me and we'll talk it through!

 

You could send your diff to unatrx, as i did. I changed the ratio from 3.07 to a 3.46 and for I think $300 + shipping both ways also got a new wave-trak at the same time new tcu tuned to the 3.46 works great. jim

 

My wavetrac did not fit in the case. I imagine if the case was spread it would go in but the way I had my rig set up I couldn't have it on while putting the diff in, so I took a dremmel and shaved a very very small amount off one spot on the lip if the case and she slid right in.

Just an FYI for others that may run into it.

 

Nothing comes up when I type Unatrx in Google. *shrug*

 

I think this is the reference. I googled "unatrx differential"

http://www.gounitrax.com/mercedes.htm

 

You got all that for how much? + 300 bucks?

unitrax can program your tcu for a 3.46 gears?

Sorry I don't quite get your post. Informative but, a little vague. Could you elaborate?

 

Highly suspect.

 

I have spoken to ProGear here in SD. I will purchase the Wavetrac, bring them them the whole unit, and they will install and configure the backlash. Just looking for the best prices on Wavetrac.

Yes, taking it out and putting it in - couple weekends, and may as well do ALL bushings

 

I think the best price I found was on eBay, 1050 or 1100 I think.

 

I had Leistung Autohaus in Westminster, CA install my Wavetrac. He's an official dealer too. Didn't take him much time to do and very reasonably priced.

 

Have my HAG215 apart and Wavetrac sitting in the shop, just received my Fowler dial indicator. Thank you again for this write-up.

 

If any of you guys are still getting notif's from this thread, do you know dealership p/n's for the shims? WT wants $14.00ea + shipping and the turnaround makes it worse.
I need a better shim snap-ring resource. Do you guys have leftovers?

Thanks.

 

What's WT? (Sorry, brain fart!) Do they have them on their website? Got a link? I can dig around in my parts bin later today and see if I have the part numbers.

 

OK, I'm up to speed now. You are talking about the snap rings available from Wavetrac: https://autotech.com/185wk-hag-215-s...84-4-46mm.html

$14 each is a bargain. What's the turnaround time?

The ones I got from the Mercedes were their original thickness; they would need to be precision ground thinner by at least one full mm. Luckily, when I did my install, I was able to reuse my original pieces and only had to take a couple thou off, which I did by hand. If that hadn't worked, I would have been looking for a precision grinding service.