W126 m103 auto to manual conversion

[Deleted member 11979]

Im in need of some help here.

I’ve previously converted a w124 from auto to manual and it was very straightforward.

I now have a w126 300se and would like to do the same thing.

Had anyone done this? The spannering would be easy enough with all w126 parts, it’s just finding them, so I need to know what gear linkage, clutch/brake pedal assembly, gearbox cross member and other associates but would fit from probably another Mercedes.

The gearbox itself is readily available and I have sourced the correct one, but am looking in vain for the ancillary parts.

Any help would be greatly appreciated

Thank you

 

[grober]

According to this thread the pedal assembly and gear shift from a manual W123 can be used with minor modifications- e.g. selector rods extended by 3 inches. Makes sense ---they are of the same era. The only PETROL manual cars were the early M 110 engined 280s I believe?
w126 manual trans - PeachParts Mercedes-Benz Forum

I would suggest looking at the early diesel engined models here [ slow to load] STAR TekInfo unfortunately no manual petrols in USA but some usefull info all the same


https://www.startekinfo.com/StarTek/outside/12253/program/Chassis/29-320.pdf

 

[Deleted member 11979]

Thanks grober, the 260se and 300se were available as manual throughout production but are clearly a very rare sight.

I’ll source the w123 parts and see what can be done, I think as you say, it makes sense it’s the nearest available.

The auto gearbox in the really dates it, and doesn’t allow the engine to give its best at all!

 

[Bellow]

How similar are W124 parts? Newer and further from W123/6 to be of use? There'll be more manual W124s out there than W126s.

 

[Deleted member 11979]

How similar are W124 parts? Newer and further from W123/6 to be of use? There'll be more manual W124s out there than W126s.

Good idea and my first port of call but w124 has cable Speedo drive and w126 electronic, the gearbox is the same aside from that, linkages and pedals dissimilar sadly

 

[Bellow]

Re speedo. If you can 'create' a speed signal, it might be possible to then calibrate it to correctly drive the W126 speedo via a gizmo used by those who fit bike engines into cars when the different wheel size and final drive ratio corrupts the speed reading on the bike speedo being fed from a sensor on the gearbox.

 

[Deleted member 11979]

Re speedo. If you can 'create' a speed signal, it might be possible to then calibrate it to correctly drive the W126 speedo via a gizmo used by those who fit bike engines into cars when the different wheel size and final drive ratio corrupts the speed reading on the bike speedo being fed from a sensor on the gearbox.

The other thing I was thinking was just put a cable speedo in the cluster, they will fit. Anyway, I think I’ve found a box (waiting for its arrival) so it’s just the other bits

 

[Bellow]

Occurred to me later - will the W126 if it has an electronic speedo not just read from the wheel sensors present for ABS?

 

[Deleted member 11979]

Occurred to me later - will the W126 if it has an electronic speedo not just read from the wheel sensors present for ABS?

No, there seems to be a plug on the gearbox output that sends a signal somewhere, this isn’t going to be straight forward but it’ll transform the car

 

[Bellow]

No, there seems to be a plug on the gearbox output that sends a signal somewhere, this isn’t going to be straight forward but it’ll transform the car

Presumably, the manual box has only provision for a mechanical cable (in which case mechanical speedo an option) or does it have an electrical sender as per the auto box?
If manual box is mechanical and wont accept the sender from the auto box (probable) then by counting its 'teeth' and cribbing from there, it may be possible to create an external sender somewhere between the box and diff. Prop shaft speed is what counts (and needs to be counted) here.

Presumably (again!), the auto box is old school hydraulic control only - no electronic control? If the latter, the engine will likely miss its signals and create all sorts of problems. I'm guessing its hydraulic hence its unresponsive nature.

 

[219]

Manual W126 was quite common on the continent - try eBay.de

 

[219]

Oh , R107 & C107 were of the same basis , as was W116

 

[Deleted member 11979]

Presumably, the manual box has only provision for a mechanical cable (in which case mechanical speedo an option) or does it have an electrical sender as per the auto box?
If manual box is mechanical and wont accept the sender from the auto box (probable) then by counting its 'teeth' and cribbing from there, it may be possible to create an external sender somewhere between the box and diff. Prop shaft speed is what counts (and needs to be counted) here.

Presumably (again!), the auto box is old school hydraulic control only - no electronic control? If the latter, the engine will likely miss its signals and create all sorts of problems. I'm guessing its hydraulic hence its unresponsive nature.

Sorry, I seem to have missed you, the manual and auto boxes have electronic senders in a w126, and cable in a w124 etc etc, so once a w126 manual box is found then all is well with the speedo.

The auto box is ok, but being 4 speeds (1st being silly low) it’s masking the potential of the engine. The manual has the same ratio in 4th as the auto, with 5th effectively being overdrive to give more relaxed motorway driving.

The difference in my w124 when I did the conversion was night and day.

 

[Bellow]

Yes, some confusion!

The gearbox itself is readily available and I have sourced the correct one, but am looking in vain for the ancillary parts.

I read the above as you already having the box in your possession (and it lacking an electrical sender).

Sorry, I seem to have missed you, the manual and auto boxes have electronic senders in a w126, and cable in a w124 etc etc, so once a w126 manual box is found then all is well with the speedo.
.

The idea of a mechanical speedo surfaced while discussing W124 parts. I was unaware that the W126 speedo reads from the same electrical sender as its manual counterpart. Obvious now!

 

[Deleted member 11979]

Thank you Bellow for all your comments, I’ve got a gearbox arriving from Germany with the correct speedo drive (hopefully on both counts) and the seller has now found a manual gear selector so it’s getting there now.

Pontoneer, eBay.de is a favourite haunt of mine, but I’ve now found another site which is even better, basically the German version of gumtree run by eBay, small ads, search it out, it’s excellent