That would fix the odometer but the speedometer uses a magnetic barrel to drive the speedo needle.

swap the gear out of the tail housing on the transmissions.

That's not how the speedos are calibrated in these cars.

The transmission drive is identical in all of MB's models. What changes is the speedometer calibration based on the differential ratio.

So you probably want to get the speedo out of the car you get the diff from. Or if you are feeling very generous drive around with your speedo way off and sell the speedo to me (if it came out of a car with a 2.47, it was already gone out of the car my diff came out of)

Unfortunately the speedo on a w126 2.47 ratio is electronic and will not work on a w123 except the 1981 TD.

Then swap the tailhousing from a W126 300SD.

I could easily be wrong but I think they went electronic in about 85 (when they also changed the diff mounts) and the ones before (I don't know how long before) were interchangeable.

anybody have any idea what w116 years we are talking? put close to 10k on the 2.47 and it is outstanding..
but it has been just a little bit tall, and need to be watching the speed.:D the xcntry cruise was exceptional though.:thumbsup:

Not sure on the years, but here is a reference list of potential diffs found in this thread

R107
---------
380SL,SLC RATIO 1:2.47

380SL,SLC,560SL RATIO 1:2.47 ABS

450SL,SLC RATIO 1:2.65

450SL,SLC RATIO 1:3.06

W116
----------
280S,SE RATIO 1:3.69

300SD RATIO 1:3.07

450SE.SEL RATIO 1:3.06

450SE.SEL RATIO 1:2.65

W123
----------
230,240D RATIO 1:3.69

280E RATIO 1:3.58

300D RATIO 1:3.46

300DT 85 RATIO 1:2.88

300DT TO 84 RATIO 1:3.07

W126
----------
300SD 85 RATIO 1:2.88 ABS

300SD TO 85 RATIO 1:3.07

300SDL RATIO 1:2.88 ABS

300SE,SEL RATIO 1:3.46

380,500 RATIO 1:2.47

380,500,560SEL RATIO 1:2.47 ABS

420SEL RATIO 1:2.47

W124
----------
260E RATIO 1:3.27

300D 1987 RATIO 1:2.65

300E RATIO 1:3.07



Side Note.. I believe the 2.65 is a LSD, 2.47 off a 420SEL and 560SEL is a LSD and 3.27 from some W124 are LSDs.

Correct me if I'm wrong, but everything on the list except for the w126 and the w124 will work on the w123 right?

My understanding is w116, early r107s, and first generation w126 (diesels versions are direct plug in and play) would mount up to the w123, but may require change of flange to accommodate the w123 flex disk and has to be mounted with a slight tilt to get a proper angle for the driveshaft. . All W124 and later generation w126 will not work because of different mounting.

True to some extent, but actually all w126 are electronic. All w123s are most likely cable driven except the '81 TD and all w116 is cable driven.

Anybody else have any more info on this (specifically to the w116 2.65)?:bulb: