wonder if a 2.88 rear out of a '85 300D will swap into a 116 1980 300SD ?
From fastlane I see that the diff mounts are the same part number, but the side seals are different ????

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1982 300SD (214 k, excellent shape) kidmobile running mostly biodiesel, gets 31 mpg hwy with 2.82 rear from a euro 500SEL



1976 115 body 240D 4-speed (traded for Jeep parts) - Engine lives on in my CJ7

I believe if you get the right shim rings, it will work.
First, my experience on this: I bought what was supposed to be a W123 differential, low mileage, with guarantee etc. It fit the chassis (my '79 300TD) but then I saw my tires were wearing on the outer edges. The car appeared to be higher in the back. After a close look we discovered the diff was from a 300SD. After getting thinner shims (MB kit $50) the distance was properly compensated. The W123 differential casing was just a little thinner measured from side to side at the faces where side seals are. I couldn't believe the shim rings were that critical, but they are.
So, the reverse might be your problem and if you didn't take this into account. your axles might be too short where they meet the hubs, because I believe the 2.88 W123 case is thinner than the SD case.
BTW after putting a W123 2.88 differential in my wife's '83 300D it became a real pleasure to drive especially on the highway over 75 - 80 MPH, the engine really loves it!
As a side benefit, the speedometer that previously read fast became almost perfectly calibrated at no extra cost!
DDH

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

I wonder if the carrier and ring and pinion would be replaceable, in that case I could use the ones out of the 123 in the 116, or is the carrier limited by case size ?

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1982 300SD (214 k, excellent shape) kidmobile running mostly biodiesel, gets 31 mpg hwy with 2.82 rear from a euro 500SEL



1976 115 body 240D 4-speed (traded for Jeep parts) - Engine lives on in my CJ7

Swapping the ring & pinion is doable, but requires that the pinion bearing pre-load is set properly. I've been told that setting the pre-load is more of an art than a science, and it's real easy to mess it up and ruin the R&P.

For this reason, and the fact that a shop will charge a fortune to do the R&P swap, IMHO it's a far better bet to swap the entire differential out...it's probably cheaper, and you don't have to deal with the pre-load.

Just my $.02...good luck!

BTW, I love my 2.88's!!

I want to try replacing my 80 300SD 3.07 with a 2.88 from a 85 300SD. Please try it and let me know how well it works!

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1980 300SD Manganese Brown Metallic Clearcoat 248k
1979 300SD White 148 k
1984 300D Silver project car for daughter
1982 300D wrecked
1980 300SD 310K not running