116 to 126 Differential swap (with pics) - PeachParts Mercedes-Benz Forum

Johnhef · #1 01-10-2009, 10:54 AM

I believe this belongs here, since I was going for performance

I wanted to swap something else into my 83 500SEC, over the 2.24 gear it came with. The limited slip in it was shot since I bought it, so I figured I would look for something taller as well. Originally I thought I could use one from a 560SEL, since not many people seemed to know for sure. It was offered to me for $175, including the axles and would have ABS and the Limited Slip in a 2.47 gearing. I knew the rear cover was different, but I thought all I had to do was swap the cover with my old one. After locating the document in the FSM, I realized it wasn't that easy. I did however find out that it looked like just about any one from a 107, 114, 115, 116, 123 and 126 would swap, up to 9/85. After some more research in the EPC to see what models came with what gearings, I set out to find someone parting a 6.9, where I could get a 2.65 Limited Slip from. Easier said then done though. After looking for awhile and having PM's not returned inquiring about 6.9 parts cars, I came across Pooka's post in the for sale section again for a 3.07 from a 1973 450SE. He pulled it in 1988, and iirc he said it had somewhere around 80k on it.

He sent some pictures and from what I could tell and what I knew, it seemed it would work. He sent it out and I recieved it this past Monday, and I got the bug to try to mess with it Thursday night. I decided I wanted to use my axles since the boots were in better shape and they were the flanged type. After taking some crude measurements, it semed like everything was the same size, so I started removing my old one. After getting it out and measuring everything, I was happy, it was all exactly the same sizing! Everything swapped PERFECTLY! So now my 500SEC has a 3.07 LSD, but minus ABS, which I usually unplug when doing auto-x anyways so I wont miss it too much. SLS will be next to go if we can ever get the Bilstein B8 Sprint (basically, the sport model) shocks over here.

--------------------------------------------------------------------------
Large Center Piece,
models: 107.023,024,025,026,043,044,045,046; 116.028,029,03x 126.03x,04x
The breather is located on the right on the rear axle housing. On models 126.03x/04x
the breather is located at the left on the rear axle housing starting Oct 81 to Nov 82.
The two lateral bearing caps are fastened with 8 screws. The hole circle diameter of
the universal joint flange on models 107.023/025/043/045, 116.028/029 and 126.032/033
up to Sep 1980 amounts to 90mm. On models 107.024/025/026/044/045/046 and 126.032/033
starting Oct 1980 amounts to 110mm.

Small Center Piece (with lateral bearing caps)
models: 107.022/042, 114, 115, 116.020/024/025/120, 123
The breather is located on the end cover. The two lateral bearing caps are each
fastened by 6 screws. Models 107.022/.042 and 123 are provided with this center piece
as standard equipment up to January 1981.

Small Center Piece (without lateral caps)
models: 123, 126.02x
The diameter of the radial sealing rings is larger and is provided with an alternate
spiral thread. Models 107.022/042 and 123 are provided with this center piece as
standard equipment starting february 1981.

--------------------------------------------------------------------------

Johnhef · #2 01-10-2009, 10:55 AM

Here goes nothing, this is the 116 diff and axles that came in the mail

The stock Euro 2.24 LSD in my SEC

The 116 diff in black and 126 diff in rust.

2.24

under the rust somewhere is the rating

Johnhef · #3 01-10-2009, 10:58 AM

2.24, leaking side seal

3.07, no leaks

116 axle and 126 axle flange

side by side

3.07 with the 126 axle flanges installed

Type of oil used, Castrol 75w-140, MB stocks it for the newer AMG and SLR models.

Johnhef · #4 01-10-2009, 10:59 AM

Rear cover plates, 3.07 on the left

Rear cover bolt lengths, 2.24 on the left

pretty shiny chunk of metal

Awfully empty up there

The crazy mechanic I had do the work for me

Just enough oil

The finished product

Achtung! Special Oil tag goes here!

3.07 stamp

All done, 10pm and time to gtf home

Roncallo · #5 01-10-2009, 11:47 AM

Very cool and informative post. I could have really used info like this for my 86 560SL to 96 SL600 rear end swap. It appears that MB rears are not very standard, each swap is a new adventure.

May I trouble you fro three more dimensions.

1) Bolt circle diameter for the side bearing retainers for both center pieces.
2) Diameter of the 126 inner CV vibration weights. Also are these weights removable.
3) Length of 126 axle from inboard CV mount flange

LUVMBDiesels · #6 01-10-2009, 12:05 PM

John,

Great job! You just eat and breathe these things, don't ya!

Why didn't you go with the 2.47 I gave you?

Also, where on the original diff does the ABS hook up? Both cases looked the same to me. I thought the ABS sensor was on the axle flange. Am I wrong?

How does she run with the taller gears? How far off is the speedo?

Johnhef · #7 01-10-2009, 02:24 PM

Quote:

Originally Posted by LUVMBDiesels

John,
Why didn't you go with the 2.47 I gave you?

Your 2.47 was from a 420SEL, iirc- It would not work in my car, or your 300SD for that matter. It will however, bolt in to your 300SDL and of course, make it a bit slower, but should increase MPG.

Quote:

Originally Posted by LUVMBDiesels

Also, where on the original diff does the ABS hook up? Both cases looked the same to me. I thought the ABS sensor was on the axle flange. Am I wrong?

You can see it in the pic showing the pinion flanges on both of them on the counter. the rusty one has a nub sticking out toward the left just behind the flange, thats where the sensor pickup is.

Quote:

Originally Posted by LUVMBDiesels

How does she run with the taller gears? How far off is the speedo?

Much quicker now, I took video before and after but it came out really dark, so I'm going to redo it. 0-60 before was 8 seconds. Speedo was under before by a small percentage (55mph was really 60), but now is over by a greater percentage (50 is really 40; 100 is really 80 and 120 is about 105)

Johnhef · #8 01-10-2009, 02:17 PM

Quote:

Originally Posted by Roncallo

Very cool and informative post. I could have really used info like this for my 86 560SL to 96 SL600 rear end swap. It appears that MB rears are not very standard, each swap is a new adventure.

May I trouble you fro three more dimensions.

1) Bolt circle diameter for the side bearing retainers for both center pieces.
2) Diameter of the 126 inner CV vibration weights. Also are these weights removable.
3) Length of 126 axle from inboard CV mount flange

John, you'll have to help me understand which parts you want, do you mind using the pics I posted and marking the spots you're referring to?

I don't believe the weights are removable- I only glanced at them when it was apart and I believe it was all one piece.

Roncallo · #9 01-10-2009, 04:32 PM

Quote:

Originally Posted by Johnhef

John, you'll have to help me understand which parts you want, do you mind using the pics I posted and marking the spots you're referring to?

I don't believe the weights are removable- I only glanced at them when it was apart and I believe it was all one piece.

In the picture titled "2:24 Leaks" and also in the picture that titled "3:07 No Leaks", I need to know the bolt circles for those seal/ bearing housings.

In the picture tilted "116 axle and 126 axle flange", your thumb is on the weight that I need a diameter for.

I attached a picture of an axle from a 560SL. It measures ~19 7/8" when compressed from the tip of the spline to the mounting flange bolt circle where I have the pencil. I'm trying to find drive shafts that are about 5/8" shorter to accommodate that 96 SL600 rear that is in the background.

Johnhef · #10 01-11-2009, 10:30 PM

Bolt circles- the outer diameter of the pieces as in outside the ring of bolts or??

I dont think I've got a caliper big enough to measure the weights, but I'll try. If I have to guesstimate, wil that be ok? since its already in the car.
I believe these axles are the same length- I recall a rough measurement of 21" when comparing the axles to see if they were the same length but I may have measured from a different spot then you.

Roncallo · #11 01-11-2009, 11:12 PM

Quote:

Originally Posted by Johnhef

Bolt circles- the outer diameter of the pieces as in outside the ring of bolts or??

I dont think I've got a caliper big enough to measure the weights, but I'll try. If I have to guesstimate, wil that be ok? since its already in the car.
I believe these axles are the same length- I recall a rough measurement of 21" when comparing the axles to see if they were the same length but I may have measured from a different spot then you.

I'm trying to find out if my wheel speed sensor mounts will also work for a 126 rear with those weights. Anything over 5 1/2" would be to big. As far as the bolt circle diameter I just remembered I have a 107 rear which I know has the same construction.

Don't go making a trip under your car just for me.

Thanks JR

Johnhef · #12 01-12-2009, 09:37 PM

well I got this pic today off the old diff, is this the dimension you wanted?

its showing 5.5 inches.

Roncallo · #13 01-12-2009, 11:36 PM

Quote:

Originally Posted by Johnhef

well I got this pic today off the old diff, is this the dimension you wanted?

its showing 5.5 inches.

Thank you John.

That means my wheel speed sensors wont fit on a 126 with those weights. I may have to make another revision for 126 owners.

Dee8go · #14 01-13-2009, 10:08 AM

Where are the speed sensors on that? Did you sand blast the rear cover or just paint it? That looks great. I didn't see your new 0-60 time. What is that?

Roncallo · #15 01-13-2009, 06:22 PM

Quote:

Originally Posted by Dee8go

Where are the speed sensors on that? Did you sand blast the rear cover or just paint it? That looks great. I didn't see your new 0-60 time. What is that?

There are no wheel speed sensors on a 126. I'm just designing external wheel speed sensors mounts so a 5 speed 722.6 transmission can be used earlier cars. But the 126 presents a special challenge with those weights. I was tying to make as universal a solution as possible. The ones I have on my 129 rear will fit the 107 rear.

Wheel speed sensors are not required to use the 722.6 trans if you use an aftermarket trans controller like PCS. But at least drive shaft speed will need to be used and that could be a signal taken from the ABS sensor.

I do not yet have clear confirmation but I believe the 722.6 transmission will bolt up to an M117 engine if you use a bell housing from a 1996 to 1998 SL500.