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Premium Member
2012 CL550 4MATIC Coupe
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Discussion Starter #1 (Edited)
Anatomy of a Differential ... Rebuild Repair R&R DIY

Well most of you have seen my DIY on the axle rebuild to stop the shuddering upon acceleration. The shuddering was from the support bracket and bearing being bad and also the U-Joint was bad. I got the axle out of the '86 that my motor came out of because the UJ was good in that one. This Diff is a 2.47 non LSD. I plan to get an LSD when I do the motor swap in the spring. In the meantime this one was leaking badly as most of you saw so it needed to be rebuild.

It is an easy enough process. (GEN II here guys..) Remove the mounts and the axles and get it on a bench.

First open the drain and fill plugs and drain the oil into a pan. They may be hard to open, mine were but did open.

Then take the 8 bolts off the rear cover plate and set aside. There ared 8 bolts on each side cover plate. Remove those and make sire you mark which side is which. There are two cir-clips that hold each axle shaft mounts, one on each side. Once those are out then the shaft mounts will come out and then the ring gear will come out.

Wash all of the parts in a degreaser and clean appropriately,

Here is the housing looking at the right side looking forward:



Another view:



And the back cover and the old seals:



And looking into the housing we see the pinion gear. This is what attaches to the driveshaft on the front of the Diff.



Here is the Ring Gear:



It is this relationship between the pinon and ring gear that sets the ratio.

The left:



And the right:



Each axle mount goes into the ring gear via the splines.

Here are the O-Rings and seals:







Well that's about it. I got the new seals right here from MB and I will do the rebuild tomorrow.

I hope you enjoyed!
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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Good write up.

I have a spare LSD off the same Gen I euro SEC the 10:1 500 engine and tranny came out of.
Never looked what the ratio is though.
 

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Premium Member
2012 CL550 4MATIC Coupe
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Discussion Starter #3 (Edited)
Good write up.

I have a spare LSD off the same Gen I euro SEC the 10:1 500 engine and tranny came out of.
Never looked what the ratio is though.
If you come across a Gen II LSD I would be most interested...

I am supposed to pickup Charlie at noon and we are going to trip by there to the yard. Will you be there?
 

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Premium Member
2012 CL550 4MATIC Coupe
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Discussion Starter #4
And yes Roy, I am going to shoot the outer casing black, but not PC it. Just a coat of Black Hi Temp Spray Paint. Spruce it up a little.
 

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2004 Acura TL, 1999 GMC Yukon
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Is the late gen 1 diff with the allen bolts the same as a gen 2 diff?
 

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Mercedes
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Excellent write-up! These kind of posts with pictures is what makes this forum great:thumbsup:

Dimm... to answer your question in a word, no. The late Gen I is different than a Gen II in the way it mounts. There's no difference between a "late" Gen I or "early" Gen I... they're the same.
 

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2012 CL550 4MATIC Coupe
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Discussion Starter #10 (Edited)
Part II - The re-assembly

Okay, so today we are going to tackle the rebuild.

In the rebuild kit there are three seals and 2 O-Rings. The O-rings are identical and 2 of the 3 seals are the same and one seal is larger.

That is the one we'll start with. It goes on the from of the Diff in the pinion gear. Grease the inside of the seal with bearing grease like this:



Here is the front of the Diff looking at the driveshaft side. The Flex Disk Collar fits onto that spline:



Next, you need to GENTLY (and I mean GENTLY) hammer in the seal with the rubber seal on the inside:



Keep going:



Hammer all the way around so that the seal sit evenly:



Next, the Flex Disk Collar sits down in there:



Until Seated:



Here is the retaining nut:



A work about the nut. You just want to lightly screw the nut on bot do not tighten or torque the retaining nut just yet. You need to have the Ring Gear in place and braced with a prybar that you can tighten it.

Okay, so next do one of the axle seals the same way:



And again carefully tap it into place:

 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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If you come across a Gen II LSD I would be most interested...

I am supposed to pickup Charlie at noon and we are going to trip by there to the yard. Will you be there?
Not today, nor tomorrow.
I hope you took a closer look under the black SEC Kurt got the door off?
Didn't all U.S. market SEC come with LSD?
Cheers
 

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2012 CL550 4MATIC Coupe
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Discussion Starter #12 (Edited)


There:



Here is the inside:



Grease the O-Ring and put it on the the side plate. You can see the inner bearing race that the Ring Gear bearings seat into:



Insert the Ring gear and make sure it is vertical and then carefully insert the side axle plate. The side plate is a tight fit and you want to becareful you do not laterally torque it. Insert two or three bolts on opposite side and work each one a little at a time until it is all the way down.







You can see the ring gear cocked here:



This is not how it is supposed to be. You can see on the right hand side the bearings are not seated properly in the race. Place the Ring Gear in the side race properly:



And sit it on that side:

 

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2012 CL550 4MATIC Coupe
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Discussion Starter #13 (Edited)
Next put the opposing plate on ensuring you put a new O-Ring in first. Line it up and ensure that the holes line up.



You may have to give it a rap with the hammer gently to align it.



Use a screwdriver and GENTLY rap it:



Until aligned:



There:



Here is a view from th rear at the Ring Gear and you can see it sitting square in the races:



Next insert the Axle shaft mount:



The Cir-Clip goes in there:



It's a bit hard to get in there:



Here it is seated:

 

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2012 CL550 4MATIC Coupe
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Discussion Starter #14 (Edited)
Completed side:



Here is the other side:



Set the Clip in place:



And pop it in:



Done:



Next what you do is to brace the Ring Gear and then tighten the front Pinion nut. (Sorry no pic)

Okay, next we are ready for the rear case cover to go on:



Put the rest on and torque them down. There are 8 17MM bolts.

After the bolts are torqued down you can then give it a nice coat of black paint to spruce it up a bit.

Well that's about it.. I will take some finished pics tomorrow and post...

I hope this was informative....
 

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2004 Acura TL, 1999 GMC Yukon
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Mike, I've never been inside a diff before, with my understanding of them being dimm at best. Thanks for an excellent post.
 

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1987 Mercedes Benz 420 SEL, 2004 Cadillac DTS
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mclare, I agree with dimm, thanks for an excellent post.
If the authors of the manuals were as precise as your post, repairs would be much simpler
for those who do not have puters.
We who have puters are fortunate that members such as yourself take the time to perform these repairs and post these articles.
 

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Premium Member
Tribute 500SEC AMG Widebody
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Nice write up michael! Who performed the diff work?
 

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2012 CL550 4MATIC Coupe
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9,993 Posts
Discussion Starter #18
Not today, nor tomorrow.
I hope you took a closer look under the black SEC Kurt got the door off?
Didn't all U.S. market SEC come with LSD?
Cheers
Thanks H! I will check it out and see... When do you think they will crush that car? I was there yesterday with Charlie and it was still there...

M
 

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Premium Member
2012 CL550 4MATIC Coupe
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9,993 Posts
Discussion Starter #19
Nice write up michael! Who performed the work, don't recognize the fingers?
Good Spotting Henric! That is Bill, one of Dragi's Mechanics. A very competent mechanic and a really nice guy too. He was very patient with me and show me every step of the way and let me take the pics for the board. When I get my LSD Diff, I will take that apart myself next time. It's really very easy. The hard part is getting out the old seals and the axle mounts out. You have to be careful there.

But he's a cool guy and he even said "Go get a can of paint and I'll spray it when I mount it to clean up the look of it a bit"

Henric, you going tonight to "Thunder Road"?
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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Thanks H! I will check it out and see... When do you think they will crush that car? I was there yesterday with Charlie and it was still there...

M
The clunkers are crushed after max 3 weeks.
 
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