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3rd Pedal

Started by sutekh, 01 April 2022, 08:32 AM

sutekh

As a card-carrying member of the manual gearbox preservation society, I've been toying with the idea of swapping my 300SD. I'd be the first to admit that a standard trans isn't necessarily a good fit with the character and intention of every car, and my initial assessment was that it wouldn't be for a w116.

If I owned a 2.8, a 4.5, ore even a 6.9, I think I'd retain that opinion, but... this OM617 needs a few more cogs IMO to stay within its narrower sweet spot. Of even greater importance, I'm thus far not a fan of hearing the poor old thing howling near 3,700 RPM while travelling at modern freeway speeds.

I've swapped a few other cars over the years, and have all the right equipment (including a lift), so that doesn't scare me, but in each of those cases, a factory (or at least common community supported) option was available. This would be a bigger one-off project requiring a lot more R&D! I do love a good challenge though :)

Starting small, I went looking for pedal assemblies, and although they certainly exist for the w116, I didn't turn up anything currently available after an exhaustive search (including DE eBay). I did find and now own this clutch pedal assembly from a w114/w115 though:

s-l1600 (1).jpgs-l1600.jpg

After staring cross-eyed at pictures of this guy and several online images of w116 clutch pedal assemblies, everything looked like it should line up and I'm happy to confirm that's true! The 3rd pedal, its spring, stop, and master cylinder bracket all bolted right onto my 300SDs' aluminum pedal carrier. I'm going to sandblast and refinish all of these parts before final fitment, but this means it's game on!

As for the trans, it almost certainly won't be a Mercedes part, but I have a lot of measurements to take before developing strong opinions about what might work. The two front-running options I'm work-shopping are these:

Anyway, this will be a slow process likely taking months to evolve, but gotta start somewhere! Any input, feedback, or opinions from the group are welcome!

raueda1

Wow, great project!  Sadly all I can offer is moral support, it's way more ambitious than anything I'd dare to do.  BTW, I'm also in SLC.  If you've seem a blue 6.9 driving around (which I do a lot of), that's me.  If you need a hand, or just somebody to "advise" from the peanut gallery, drop me a line.  I'd love to see the car.  Good luck and cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Bad Benzo

This is exciting!  I have a '77 280SE, and I love driving it in a spirited fashion, but I find the automatic transmission is just not exciting, even when I put it into L or S. 

My other Sonderklasse is a Euro spec 1963 220SE with a 4 speed on the column, which is an absolute riot to drive quick, but also very smooth when driving in a relaxed fashion.  For someone like you or I, having more control would certainly be worth the effort.  I think the 4 speed manual would be insufficient for my car at higher speeds, so when I make the swap, I absolutely want 5 gears.  I have a friend with a business in Lebanon who is sourcing me a factory 5 speed for my W116, but I don't anticipate that it will be here in the USA any time soon.

I'm interested in following your progress!
1963 220SE - 1977 280SE - 1986 300E AMG

sutekh

Quote from: raueda1 on 01 April 2022, 09:29 AMWow, great project!  Sadly all I can offer is moral support, it's way more ambitious than anything I'd dare to do.  BTW, I'm also in SLC.  If you've seem a blue 6.9 driving around (which I do a lot of), that's me.  If you need a hand, or just somebody to "advise" from the peanut gallery, drop me a line.  I'd love to see the car.  Good luck and cheers,

Thanks for the offer! I'll keep that in mind as things progress. I'm sure I'd remember seeing a blue 6.9 (peak w116 combo IMO) tooling around, but will certainly keep my eye out! I'm down at the South end of the valley in Draper.

Quote from: Bad Benzo on 02 April 2022, 08:46 AMThis is exciting!  I have a '77 280SE, and I love driving it in a spirited fashion, but I find the automatic transmission is just not exciting, even when I put it into L or S. 

I have a friend with a business in Lebanon who is sourcing me a factory 5 speed for my W116, but I don't anticipate that it will be here in the USA any time soon.

I'm interested in following your progress!

One thing to keep in mind, is that even the 5spd (which as you know is exceedingly rare) still has a 1:1 final drive ratio. I'd look more seriously at finding one, but it frankly doesn't solve for my biggest concern without an overdrive :/

Alec300SD

I loved the the Laycock de Normanville planetary overdrive on 'Grasshopper', my 1979 Volvo 245DL wagon.
Overdrive on demand in fourth with the mere flick of a switch was a treat.
Even better was instantly dropping down to forth for passing.
Unfortunately, I tore my left ACL years ago so I made the switch from a Volvo manual gasser to MB diesels with automatics.

For your intendeded purpose, one could (possibly) transplant in a used unit from a Volvo manual to convert a standard MB 4 speed manual to a 5 speed manual with overdrive.
New aftermarket units ($$$) are available  for manuals (and automatics) from https://www.gearvendors.com/index.html.
From what I read, my understanding is that their unit could turn a 4 speed manual into an 5-8 speed manual on demand.

To reduce engine rpm for his high speed long distance commutes the previous owner of 'Desert Rose' (my 1978 300SD) swapped in a 2.49 final drive  differential.
The car has lower revs at 65+ mph, but accelerates poorly with the 2.49 differential.
I don't take long trips often with 'Desert Rose' so I have just put in  a 3.06 differential to address the acceleration issues.

I do like the lower noise levels  obtained at highway speeds  when the 2.49 diffierential was installed.
Eventually, after an engine swap, and front suspension rebuilt, I do plan to add in a new overdrive unit to 'Desert Rose'.
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022
91 W126 300SE 'Kjetteri' new as of 02/19/2022

daantjie

Also check out Tremec.  Pricey though methinks.
Daniel
1977 450 SEL 6.9 - Astralsilber

sutekh

Quote from: Alec300SD on 02 April 2022, 10:41 AMI loved the the Laycock de Normanville planetary overdrive on 'Grasshopper', my 1979 Volvo 245DL wagon.
Overdrive on demand in fourth with the mere flick of a switch was a treat.
Even better was instantly dropping down to forth for passing.
Unfortunately, I tore my left ACL years ago so I made the switch from a Volvo manual gasser to MB diesels with automatics.

For your intended purpose, one could (possibly) transplant in a used unit from a Volvo manual to convert a standard MB 4 speed manual to a 5 speed manual with overdrive.
New aftermarket units ($$$) are available  for manuals (and automatics) from https://www.gearvendors.com/index.html.
From what I read, my understanding is that their unit could turn a 4 speed manual into an 5-8 speed manual on demand.

To reduce engine rpm for his high speed long distance commutes the previous owner of 'Desert Rose' (my 1978 300SD) swapped in a 2.49 final drive  differential.
The car has lower revs at 65+ mph, but accelerates poorly with the 2.49 differential.
I don't take long trips often with 'Desert Rose' so I have just put in  a 3.06 differential to address the acceleration issues.

I do like the lower noise levels  obtained at highway speeds  when the 2.49 diffierential was installed.
Eventually, after an engine swap, and front suspension rebuilt, I do plan to add in a new overdrive unit to 'Desert Rose'.

Interesting that you mention the Volvo OD units. I looked semi-seriously into possibly retrofitting one on a w126 300SD I had years ago. I ultimately determined (and still believe) that would be a bigger project than simply manual swapping given the wealth of OM617 adapter plates for various transmissions on the market, but an interesting idea certainly.

I was about to start acquiring parts to convert that particular car to a 722.5, which is essentially a 722.4 with a solenoid actuated OD in the tail, and had envisioned a similar "flip of a switch" arrangement. Alas, some chucklehead turned left in front of me, and that was end of that car and any associated projects.

As for the final drive gearing, I just can't do it  :) Sedate acceleration I can live with, but glacial is a bridge too far. It'd also only be good for a few hundred RPMs, while an 0.8:1 OD should put me comfortably below 3K at even > 80mph.

Quote from: daantjie on 02 April 2022, 10:53 AMAlso check out Tremec.  Pricey though methinks.

I don't believe I've ever encountered a bolt-up option from Tremec (or anyone else for that matter) with an OD? If you've got a lead I'd love to hear it. If we're talking adapter plates, which tranny I end up using will ultimately come down to fitment: Gotta fit in the tunnel and have a workable shifter position.

Bad Benzo

Quote from: sutekh on 02 April 2022, 09:00 AMOne thing to keep in mind, is that even the 5spd (which as you know is exceedingly rare) still has a 1:1 final drive ratio. I'd look more seriously at finding one, but it frankly doesn't solve for my biggest concern without an overdrive :/

According to the tech specs, the final drive was .875
1963 220SE - 1977 280SE - 1986 300E AMG

sutekh

#8
Quote from: Bad Benzo on 02 April 2022, 07:12 PMAccording to the tech specs, the final drive was .875

My mistake! I was incorrectly thinking of the 717.404. If you haven't seen it already, take a look at this (complete?) list of Merc manuals:

https://mbturbo.com/manual-transmissions/

BTW, if your friend can source two of those boxes, I'd be more than happy to turn out my pockets and couch cushions :)

gurrier

Are there any possibilities presented using parts from the TN range of vans which would facilitate
a Manual Transmission changeover.
1973 350SE

gurrier

Judging by the silence - apparently not :-[
1973 350SE

daantjie

I think the lack of traction here (no pun intended 8) ) is likely due to the fact that not many folks have done this successfully.  So you can be the trailblazer here ;D   If you do move forward might be nice to have lots of pics and step by step for the next guy.
Daniel
1977 450 SEL 6.9 - Astralsilber

gurrier

Indeed Sutekh- I agree with daantjie - this is an admirable undertaking. It will make your W116 more useful to you and thereby prolong your ownership.
Presumably our involvement with the forum is for the purpose of sharing knowledge/enlightening other members with a view to envigorating the W116 general ownership experience, and not exclusive to one particular segment of the range. 
Sometimes - God Forbid - as we say - we might ask stupid questions. 
From my admittedly limited knowledge I thought that the vans were fitted with the 617 engine, many/most being manual.  I take it that the avenue of using parts from the vans transmissions have been discounted.

I look forward to seeing your progress.

1973 350SE

Casey

Oh lucky you...

I had a 5-speed MB trans that I intended to do this with once, but like many of my crazy dreams, it never happened.  Also had a 6.9 with a blown engine and a 300TD engine that I thought I might transplant into it, along with a manual transmission, but it never happened and everything was sold for peanuts in the end.

Enjoy your adventures and best of luck!

sutekh

Quote from: daantjie on 05 April 2022, 09:52 AMI think the lack of traction here (no pun intended 8) ) is likely due to the fact that not many folks have done this successfully.  So you can be the trailblazer here ;D   If you do move forward might be nice to have lots of pics and step by step for the next guy.

I don't think I've seen a documented account of it this having been accomplished on a w116 (and believe me, I've looked!), but it's a common enough swap on w123s. I'll be sure to take plenty of pics once the greasy side is up in the air :)

By way of update, I believe I've tracked down a suitable shifter as well. The below pictured part is on its way to me from Eastern Europe, and was originally from a w126 with a 5-speed 717.402 trans. No documentation suggests this will fit the w116, but having stared at lots of pics of shifters for each model and their respective mounting locations, I'm hopeful that it'll bolt right up.

The clutch / pressure plate / throw-out are readily available and I have a lead on a flywheel, so that just leaves the forward driveshaft (hoping to have a local driveline shop I've used for similar work on other swaps modify mine) and of course, the very rare and very expensive 717.40[02]. More to come...