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Converting my 1977 280SE to a 4 speed manual

Started by Bad Benzo, 04 September 2022, 06:09 AM

Bad Benzo

I'm establishing this thread to keep track of my manual transmission conversion.  A local yard received a very unusual Euro spec 1975 280SE, with flat door cards, cloth seats, orthopedic driver seat, and a manual transmission.  At first, I was only interested in the bumpers, differential, and some trim, but once I discovered that it had a manual transmission, I made special plans to take that as well.

Reasons why I am converting my perfectly running automatic car to manual:

1: Most of my other cars have a manual transmission, including my 1963 220SE.  I thoroughly enjoy driving manual from the aspect of driver engagement.
2: I like things that are rare or uncommon.  I have a feeling there aren't many manual W116s in the USA, and putting one back on the road appeals to me.
3: I want to do something only few people have done before.
4: Since the donor is already a 1975 280SE, it is a direct fit to my 1977 280SE.  I had thought about this type of conversion before using parts from a 240D, but modifying the shifter linkage, driveshaft, and finding the correct M110 flywheel made the project seem like more effort than it was worth.  Now that I have access to all the correct parts, it seems like a no-brainer.

While I agree that the factory suspension is divine when it comes to comfort, my driving style demands something a little more sporty.  I live in an area with lots of hills, twists, and turns.  My car has been driven on the track at Watkins Glen International.  While the transmission swap is underway, my car will be treated to a full suspension overhaul, including performance lowering springs for a slightly stiffer ride and flatter cornering.
1963 220SE - 1977 280SE - 1986 300E AMG


I love that interior. Are you taking the ortho seat?
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'21 E450 Cabrio


Great project!  Looking forward to following your progress.  Cheers,
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Bad Benzo

Quote from: rumb on 04 September 2022, 08:34 AMI love that interior. Are you taking the ortho seat?

I am not taking the orthopedic seat, the interior had some rat nests and there's definitely an odor.  Most of the driver seat cushioning was found scattered across the floor and under the dash.  Someone else took the flat door cards and a few other trim pieces between yesterday and today.  25 years ago when the car was parked, this would have been a great survivor, it's unfortunate that this car came to an end this way.
1963 220SE - 1977 280SE - 1986 300E AMG

Bad Benzo

I went back today for the big pull.  This was a bit more time consuming than I had hoped, and certain items, like the pedal box, took much longer than I had anticipated.  To remove the pedal box, you need to disconnect a lot of parts; including the clutch master bolted to the pedal box, and the brake lines to the brake master. 

The exhaust was "new" but obviously a bit rusty from sitting.  Because the exhaust on my car is in poor condition, I took the exhaust off the donor, along with the Euro headers.  The transmission was fairly quick to extract, someone removed the engine mount bolts, so as soon as the driveshaft was removed, the engine tilted and the transmission housing bolts were easy to reach, including the uppers!

I grabbed the transmission, flywheel, driveshaft, pedal box, linkage, brake master reservoir, and I will return tomorrow or later this week to remove the differential.  The differential on my car doesn't have any play that I can detect, but it does make a whine that worries me.  I had a bad experience with my Dodge Ram that makes me hyper sensitive to rear end noise.  Since my car has over 500k miles, I thought getting a differential out of this car with ~147k documented miles isn't a terrible idea.  Plus, when will I find another differential for a 280SE?

1963 220SE - 1977 280SE - 1986 300E AMG


Best of luck with your task.  The extra control over your vehicle that manual transmission gives as a driving sensation certainly makes the man/machine connection more direct.
1973 350SE


Don't forget that on the M110 the crankshaft is balanced together with the flywheel , so in theory you can not just put another flywheel on.



Mercedes clearly states in the manual that if you change the flywheel you have to transfer the balance on the M110,  i think you are confusing it with m116/117 where thats not necessary.
I attached a screenshot from the german workshop manual sadly i don't have the english one.


Yes that is correct transfer imbalance from one flywheel to the other is all that is required. I have read the relevant page.


Awesome project! I'm also amassing parts to swap my 300SD, although to a 5 speed (overdrive or bust!) I'm sure you will, but be sure to grab the trans support and front section of the prop shaft. Both are specific to manual cars and among the bits I'm having the hardest time finding!


Quote from: rumb on 04 September 2022, 08:34 AMI love that interior. Are you taking the ortho seat?

A few weeks back I pulled the ortho seat bits from a '80 300D. For anyone who doesn't know, the orthopedic seat is just has a pillow underneath the seat cover on strap that can be pulled up/down from the back of the seat to adjust the lumbar. The pillow cushioning is the same material as the seat pads and the cover is just headliner material. The seat pads are identical to the standard seats minus having a hole for the strap to pass through at the top. When I get time, I'll try and 3D model the plastic bits that the strap goes through in the backer panel and get measurements on everything for if anyone would like to recreate them for their car.
75 450SEL
80 300SD- cancelled project
83 300D- 5-speed OM617
84 300D- AMG 5.4L N/A M113 6 speed
92 300D- 722.6 OM603 3.5
93 190E 2.6 Sportline LE x2- 6-speed M111 turbo, 3.0 M103
02 C320 Wagon
03 Sprinter 2500
06 E500 4Matic Wagon- AMG 5.4L NA M113

Bad Benzo

Quote from: sutekh on 12 September 2022, 07:07 PMAwesome project! I'm also amassing parts to swap my 300SD, although to a 5 speed (overdrive or bust!) I'm sure you will, but be sure to grab the trans support and front section of the prop shaft. Both are specific to manual cars and among the bits I'm having the hardest time finding!

Oh yeah, I took everything from the engine to the rear axle.  This isn't my first manual transmission swap, but it is the first time I will swap a W116.  I even took the brake master/booster since the clutch reservoir runs off of it.
1963 220SE - 1977 280SE - 1986 300E AMG


1975 280S - Australian delivered

Bad Benzo

Quote from: Nabstud on 17 March 2024, 08:19 AMHow did this conversion go?

This conversion is still in progress.  I sent the flywheel out to be resurfaced and it looks great.  A short time after starting this thread, the original M110 in my car spun a rod bearing after the oil galleys were clogged by some sludge and debris from the cam box. 

Needless to say, this job became very complex very quickly.  I began the process to refurbish and adapt the Euro D-Jet M110 from the donor to match my K-Jet M110.  I sold my W124 300E AMG and W108 280SE 4.5 to free up funds to direct toward the W116 rebuild.  I hope to have the car running again by the end of summer.
1963 220SE - 1977 280SE - 1986 300E AMG