#1 - replaced what remained of the stock suspension, to make it do silly things
Time for #2 - the gearbox that had been slowly breaking for a while finally broke*, so I took the opportunity (/was forced) to make the upgrade I'd planned to make when I get round to fitting the superturbo engine
*flare on 3>4 shift got bigger & bigger, until finally 4th wouldn't engage at all. Not a fluid issue. 170k mile old gearbox said no.
Fortunately I had this C270 CDi, which was my daily while the S124 was off the road previously, and has the 2nd strongest OE Benz auto box with the right fitment for an OM606 (only rare af V8 gearboxes are stronger) - for my fellow nerds, it is a 722.640, which is rated to 580Nms.
Shoink!
If you haven't curse word fluid all over the floor, are you even removing a gearbox?
I then dropped it off at this awesome local specialist for a service. Wish I'd taken some photos inside. Place was awesome, proper old school, tons of old machinery, smelled amazing, both the engineers I met looked about 70. Highly highly recommended if you need an auto box looking at. Was criminally cheap too - iirc £65 for a strip down, check over/service & rebuild with new gaskets. Crazy.
The 'box ultimately received a clean bill of health. Excellent.
Had some nice customer cars in for work (they do a removal/reinstall option too)
While that was away I got the 124 in & started pulling it apart:
New & old, side by side:
Clearly the new one is much bigger. As well as having another gear, it's also a lot stronger.
Having put it in & out a couple of times to get everything correct I can confirm it juuuuuuust fits in a 124 trans tunnel without hitting anything
Collection of trans mount parts from the 2 gearboxes / cars:
Only some measuring / trial fitting & drilling of new holes in the 124 cross member was required to fit the 722.640 mount to it:
Next issue, prop lengths..
Right is S124, left is W203 (C270 gearbox donor)
Rear section has to stay OE (obviously the distance between the diff & the centre mount / bearing carrier hasn't changed), but the mount / bearing was goosed.
Popped a new one on:
Front section I had options:
S124 / W203 / W210 (turbo engine donor - see few posts ago)
W203 one looks about right:
Next up, shifter.. The W210 I broke for the turbo OM606 I plan to fit to this car does actually have a 722.6xx gearbox, albeit a weaker one, so the 'normal' PRND4321 shifter from that would actually drop right in here, BUT I really wanted to use the tiptronic shifter from the C270. I much prefer autos in a daily, but like to have full control, for spirited driving, towing etc, so the tiptronic is a desirable option for me. I really like it in the E31, and the gearbox controller I'll mention in a bit has the capability to use one. So... This is where it needs to go:
But it's a lot bigger than the OE shifter, and this area appears to have all the words wiring (including a ton of stereo stuff I now regret routing through here, lol)
Made some CAD of the bottom of the shifter, so I know where to cut, and where to drill the mounting holes:
Also moved a load of wiring, especially that mass of earths. Then the shifter fits:
And the 'wood' trim goes neatly back into place:
Note that the new shifter body sticks up through the trim - obviously the old one did not. Still need to sort something to tidy this up.
Then the gearbox can be bolted in for the final time. Amusing array of extensions required, and a capable 2nd pair of hands - could not have done this without the daaahling Colonelk
Last bit for the shifter is the rod from the bottom of the lever to the gearbox.
Measure 8 times, cut once:
Welded back together & fitted:
There is a little bit of adjustability built in, but obviously nowhere near enough for this. Ended up not needing it even after the cut & shut. Note I also fitted new OEM flex disks / guibos at each end cos the old ones were completely goosed.
Finally, the BIG issue; this new gearbox is completely computer controlled. The 124 doesn't even have an ECU, let alone anything to control a gearbox.
The solution is one of these:
A "Stand Alone Controller for 722.6 Mercedes Gearbox" from OFGear
Not cheap, but an extremely fancy piece of kit, and there aren't really any other options.
From their website: "Classic car Modern Gearbox. You have 3 or 4 gear automatic
You get 5 Gear + Lockup + Paddle shifter + Manual mode + Free programmable width the includet LCD display, or PC program"
Note the bit about manual mode, which is what's allowing me to use the W203 PRND+/- tiptronic shifter.
First job was finding somewhere to mount/hide the controller, and route the absolute TON of wiring. Behind the airbag there is a handy pocket of space, which also allows easy-ish access to the engine bay (for TPS and boost (which I don't have any of yet)), bulkhead (for the ENORMOUS gearbox connector) and the centre console (for the tip shifter), plus power, earth etc.
Image stolen from the OFGear website:
Next up, finding somewhere to mount the LCD display. Needs to be neat, as OE-looking as possible, and not obscuring anything else.
Looked at in or below the clocks, which I've seen done, but that would be a right pita to get at, and I don't really like how they look in there. Then I was looking at the wood trim between the shifter & the ash tray, or removing the ash tray altogether, both of which would probably have worked (except I wanted the ash tray for something else). Then I noticed the rectangular air vents were very close to the same size / shape as the LCD.. bingo!
Obviously putting extra gauges, especially boost, in vents is pretty common, and the OFGear display will ultimately show boost anyway (when I have some) so it's ideal.
Take it all to bits:
Amazingly every component in these vents, even the slats/flaps, is metal. No plastic at all. So it's easy to take to bits & modify without snapping or cracking anything. The supplied LCD housing is even a very similar finish to the Benz plastics! Just needed a little sand down to fit snugly:
And feed the ribbon cables through (one for the screen, and one for the button/joystick:
Pretty damn happy with that, not gonna lie
Gearbox plug was immensely fiddly (round, no clear orientation, 8 million tiny wires..) but eventually went in. Boost sensor I just tucked out the way for now. And for the TPS I made a boo boo..
Having taken all the inlet pipework off to get to the TPS on the bottom of the pump, I came to realise that the stock TPS is just an on/off ('am I at idle?') type one, not a potentiometer type one. Plainly obvious if I'd thought about it for 8 seconds, plus I'd already scrapped the W210 by this stage, so I had to buy one off eBay
Found somewhere to mount it that the loom would reach:
And modified the throttle cable bracket so it would pull on the TPS via a generic cable:
Last thing was the shifter. This involved CAN wiring, which is far too complicated for me. Luckily I share a 'shop with some legends (mantaphil in this case) so my shortcomings are rarely an issue
And there we have it. Car basically back on the road. A lot of steps are missing (transferring the dipstick tube from the W210 turbo 606, making composite ATF cooler lines from the pile of bits, modifying the OE wiring which went to the old gearbox, but is now redundant, etc etc) but that's the gist of it. Took maybe 3 weekends, a lot of it faffing around working stuff out.
I had to do some basic setup in the controller (shift firmness mainly) but the base 'map' was mainly fine. I've fiddled with it a bit since, but it's been basically perfect. Once I do the turbo swap there will be more things to play with
(it can control a VNT turbo, for example)Things I still need to do:
There is currently nothing stopping you starting it in gear, which isn't the end of the world but isn't ideal, plus there are no reverse lights. Also annoyingly the car locks the gearbox in Park mechanically (via cables to the ignition switch & brake pedal) where as the new shifter does it electronically - so I currently have to shove my finger down the side of the shifter to the override button. This needs sorting as once I sort the trim out nicely it won't be an option. Any suggestions? Anyone solved this issue themselves?
This is the trim issue:
Bigger issue is that I now have no speedo. Old box had a mechanical speedo drive, new box does not (it's electronic in the donor car) - so I've bought this to solve that:
A SpeedHut GPS speedo driver - which a pal visiting on holiday from the US brought over for me (same one that brought the airbags on a previous trip - I dunno why she keeps agreeing to these things
). I'll hopefully have time to fit that soon...Thanks for reading
