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Garage => Mechanicals => Topic started by: Bad Benzo on 04 September 2022, 06:09 AM

Title: Converting my 1977 280SE to a 4 speed manual
Post by: Bad Benzo on 04 September 2022, 06:09 AM
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.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: rumb on 04 September 2022, 08:34 AM
I love that interior. Are you taking the ortho seat?
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: raueda1 on 04 September 2022, 09:00 AM
Great project!  Looking forward to following your progress.  Cheers,
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: Bad Benzo on 04 September 2022, 04:45 PM
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.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: Bad Benzo on 04 September 2022, 05:03 PM
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?

305541644_10104774228644565_5881364631690089739_n.jpg 
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: gurrier on 05 September 2022, 01:38 AM
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.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: ramiro on 07 September 2022, 07:42 AM
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.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: Lance on 07 September 2022, 09:08 PM
No it is not
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: ramiro on 08 September 2022, 05:23 PM
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.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: Lance on 08 September 2022, 09:19 PM
Yes that is correct transfer imbalance from one flywheel to the other is all that is required. I have read the relevant page.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: sutekh on 12 September 2022, 07:07 PM
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!
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: orientrot on 12 September 2022, 10:01 PM
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.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: Bad Benzo on 17 September 2022, 08:25 PM
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.
Title: Re: Converting my 1977 280SE to a 4 speed manual
Post by: Nabstud on 17 March 2024, 08:19 AM
How did this conversion go?