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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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Discussion Starter · #1 ·
Here is my journey of installing a 722.636 into my 300SD and having it finally work flawlessly.

I started by purchasing a used E300 transmission, shifter, driveshaft, and torque converter for almost nothing, trans condition was unknown. I used some cad assistance to design an adapter plate to mate the OM606 bellhousing to my 617 block. A few months later during my first semester at college, I picked up a transmission out of a 2001 S55 AMG, then swapped the bellhousing from the E300 onto it.
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The difference in on of the standard (left) and AMG (right) transmission clutch packs
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The adapter plate on the motor before tightening
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The 1998 E300 torque converter was a perfect match to the om617, all the bolts lined up as well as having the correct sized pilot to fit in the end of the crank/flywheel. The trans fit in the tunnel perfectly and without a problem.
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To take care of the transmission fluid cooler I just used some -6AN line and 14x1.5mm adapters to plumb the transmission into the stock cooler in the radiator.
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Here is a final undershot of the car showing how at home the transmission looks in the car. Also a custom rear trans mount.
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I used a CNC plasma cutter to make the new center console to fit the shifter from the E300 as well as hold the transmission LCD and joystick interface. With room to spare, I added a panel mount USB to access the computer as well as a Quick Charge USB phone charger with a voltage display.
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This whole setup is controlled by an OFGEAR controller from ofgear.dk which is hidden beside the drivers right leg behind the carpeted panel.
The driveshaft is a front half from the E300 cut, sleeved, and welded to the back half of a spare 300SD driveshaft. I cut them apart and made the joining sleeve on a lathe, then TIG welded the halves together in house as I couldn't find a driveshaft shop that would even touch it.

All in all I have about 6 months in this project as the time sourcing a good transmission and finishing my first college semester was time consuming. Although, drive in to drive out of my workshop was just over 7 hours. I know the 617 is old and outdated, but I have mine fitted with a Dieselmeken pump, and boost controller to up the power. This car now drives better, more comfortably, and easier than any modern car I've been in.
 

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W123 300CD, W123 300TD, W202 C250D Turbo
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491 Posts
Hi - There has been some discussion about this over in the W123 forum and great to find someone who has one this. A couple of quick questions

1. How hard was it to calibrate the W126 Speedometer to the Ofgear Controller or did you use the 722.6 output ?
2. Did you have to tune the ofgear controller or was it essentially pre-configured "out of the box"
3. How did you connect the Throttle Position Sensor ?
4. Is the rear transmission cross mount the same as that used for the 722.3 / 4 xx transmission
 

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1986/1990 W126
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16,483 Posts
No way. How did I never see this. Absolutely amazing.
 

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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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65 Posts
Discussion Starter · #5 ·
Hi - There has been some discussion about this over in the W123 forum and great to find someone who has one this. A couple of quick questions

1. How hard was it to calibrate the W126 Speedometer to the Ofgear Controller or did you use the 722.6 output ?
2. Did you have to tune the ofgear controller or was it essentially pre-configured "out of the box"
3. How did you connect the Throttle Position Sensor ?
4. Is the rear transmission cross mount the same as that used for the 722.3 / 4 xx transmission
1. The speedo was extremely easy, the w126 has an electric speedo and you simply hook up the signal wire from the Ofgear and turn it on in the settings. I used a GPS speedometer and just drove and adjusted the calibration number until they matched, quite easy. The speedo pickup is on the driveshaft, just an inductive pickup catching the bolt heads on the flex joint. Ofgear page on speedo
2. It is basically pre-configured. There is a one page "first-start sheet" that you have to do out of the box, it is essentially just picking "gas or diesel," "turbo or NA," it's all explained in the paperwork
3. My throttle position sensor setup is a little unique. I took the trans linkage from the valve cover on a spare 617 and modified it to connect to the injector pump linkage, it works phenomenally since it's connected to the actual fuel (power) input and not the pedal, thus taking out all the slop in the worn-out joints. I'll take a picture and get it on here later today if I have time...College is keeping me pretty busy.
4. You can use a regular 722.3 cross member I think...However I did not so I cannot verify. I am pretty sure you just have to drill a couple of different holes on the bottom, but I fabricated my mount from a 722.3 cross member, I just did some cutting and welding because I didn't like the way it was fitting, plus I wanted to mount my speedo pickup with a fancy bracket.

Please link to this discussion any more questions, I would love to answer them and help others down this path, it is 100% worth it.
 

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W123 300CD, W123 300TD, W202 C250D Turbo
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491 Posts
Please link to this discussion any more questions, I would love to answer them and help others down this path, it is 100% worth it.
Thanks - I will be doing the conversion so will check in with yourself and have linked to the discussion over at w123. A few more questions

1. DId you have to change the direction of the starter bolts
2. How about the 722.6xx bell housing, any mods to it
3. Can I buy from you the CNC CAD file for the adapter plate (will be much cheaper to cut it out here)?
4. Did you have to fabricate a special Park bar from the selector to the trans
5. For reverse lights and neutral start, did you make your own outputs from the selector or does the controller do it for you
 

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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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65 Posts
Discussion Starter · #7 ·
Thanks - I will be doing the conversion so will check in with yourself and have linke dot the discussion over at w123. A few more questions

1. DId you have to change the direction of the starter bolts
2. How about the 722.6xx bell housing, any mods to it
3. Can I buy from you the CNC CAD file for the adapter plate (will be much cheaper to cut it out here)?
4. Did you have to fabricate a special Park bar from the selector to the trans
5. For reverse lights and neutral start, did you make your own outputs form the selctor or does the controller do it for you
1/2. The starter bolts were just changed to shorter ones and run thru slots I cut in the bell housing to accommodate it. Not the best way honestly.
3. If I can find it, I will put it up for a very reasonable (maybe free) price. I had it laser cut from 3/8" plate by a shop near where I live, and I do not remember the price.
4. The shift linkage that came from the donor car was the perfect length range (adjustable), and no there isn't a shift interlock on mine, I disabled it. Only certain cars have it. There are write ups somewhere about it, I'd have to look around.
5. Neither of those two things work on mine haha. It will start in any gear, and the reverse lights don't work. I have plans to fix both, and yes the controller can/will handle them.
 
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06'E350 wgn,05'E320 CDI,04'E320 wgn,85'300CD,67'230SL
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135 Posts
WOW! Impressive work! Thanks for posting.
I used to tow with my 85 300SD. That OM617 motor is an ANVIL! I had to leave the tranny in 3rd and let it spin to avoid smoking the torque converter. Tranny fluid/filter changes every 15K.
375,000 miles logged on original motor and tranny and no problems. Donated it to a worthy Non-profit.That car is probably still out there running somewhere. But the 722.6 is so much better. (I have one now in my E320 Wagon) Another anvil matched up to the OM617. Sweet!
 

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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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65 Posts
Discussion Starter · #9 ·
WOW! Impressive work! Thanks for posting.
I used to tow with my 85 300SD. That OM617 motor is an ANVIL! I had to leave the tranny in 3rd and let it spin to avoid smoking the torque converter. Tranny fluid/filter changes every 15K.
375,000 miles logged on original motor and tranny and no problems. Donated it to a worthy Non-profit.That car is probably still out there running somewhere. But the 722.6 is so much better. (I have one now in my E320 Wagon) Another anvil matched up to the OM617. Sweet!
I use this thing like a tank, pulled uhauls for hours and trans never even got above 90°c

The ofgear controller is really amazing in my opinion
 

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06'E350 wgn,05'E320 CDI,04'E320 wgn,85'300CD,67'230SL
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I squeezed some 116 euro taxi springs into the rear of the 300SD to help with the tongue weight.
But your OM617 and 722.6 set-up is about as close to a diesel locomotive as a car can get! And comfy to boot!
Awesome job!!

Don't do as much hauling these days, but my E320 wagon has standard RWD and self-leveling air with the 722.6, so I can just leave it in 4th and cruise with the trailer all day. Better than any pick-up truck IMHO! But it's no indestructible 300SD!
 

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W123 300CD, W123 300TD, W202 C250D Turbo
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3. If I can find it, I will put it up for a very reasonable (maybe free) price. I had it laser cut from 3/8" plate by a shop near where I live, and I do not remember the price.
You are a college student and so some extra where with all woudln't go astray, so please set a price - besides, the tech support you are supplying here is invaluable !

What has re-motivated me on this conversion is that I went away for the long Easter break in a W123 5 Speed Wagon - Cruising in overdrive was soooo quiet and economical in comparison to my W123 coupe, which is screaming (and guzzling) on the same trip. Soo, I figure the 722.6 is the best of both worlds, auto for my laziness and torque lock overdrive for my stinginess.
 

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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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65 Posts
Discussion Starter · #12 ·
You are a college student and so some extra where with all woudln't go astray, so please set a price - besides, the tech support you are supplying here is invaluable !

What has re-motivated me on this conversion is that I went away for the long Easter break in a W123 5 Speed Wagon - Cruising in overdrive was soooo quiet and economical in comparison to my W123 coupe, which is screaming (and guzzling) on the same trip. Soo, I figure the 722.6 is the best of both worlds, auto for my laziness and torque lock overdrive for my stinginess.
Here is my throttle position sensor setup
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I will have to look around and call some people for the file. My desktop hard drive died a couple months back, but I know there's a copy of the cad file somewhere at my parents house, and at the place who made it. Its just a matter of finding it haha.
 
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'85 300TD Turbo
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Nice work Blue!! I have been considering the same thing for my 85 300TD. In the process of rebuilding my OM617.952 and I would love a more modern trans to put behind it.

I'm with Sharkey and would gladly purchase a copy of your CAD file if you are able to track it down.

Cheers!
Alex
 

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W123 300CD, W123 300TD, W202 C250D Turbo
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I think you had better give us a wide angle on that engine bay - there are a few inexplicable things on the RHS I wouldn't mind get a look at
 

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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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Discussion Starter · #15 ·
I think you had better give us a wide angle on that engine bay - there are a few inexplicable things on the RHS I wouldn't mind get a look at
Here ya go, AWIC, Hood stack, custom air filter stuff. Ask away!
2685052
 
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The 4 horns must scare the living daylights out of who ever is coming .... Nice looking engine bay

1. What is the aluminium trapezoid box
2. And the black lidded box with wing nut in the middle
3. Do you get much soot on the windscreen with the smoke stack upfront
 

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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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65 Posts
Discussion Starter · #17 ·
The 4 horns must scare the living daylights out of who ever is coming .... Nice looking engine bay

1. What is the aluminium trapezoid box
2. And the black lidded box with wing nut in the middle
3. Do you get much soot on the windscreen with the smoke stack upfront
UPDATE ON CAD FILE: I have made phone calls, and it is in the process of being tracked down!

1. That is my air to water intercooler. It's an ebay special that I modified the inlet and outlet location to fit where the turbo is, I also modified the turbo and intake manifold by adding short aluminum pipes with beads so the silicone intake doesn't blow off. It runs just plain antifreeze with a 12v pump to a tiny radiator in the grille area, next to the AC fan.
2. The black box is actually a custom electrical box I made, it houses a small fuse block and four relays that are all linked to the switch panel in the console so I can just make all my connection in the engine compartment and keep it looking nice. Next time I'm under the hood I'll take some pics of it. It's where the electric rad fan hooks up, the air compressor, intercooler water pump, and other odd things get power.
3. The only soot that ever gets on the car and stays is if the car is wet or I'm driving in the rain, because the soot will blow away if it's dry outside. The hood also collects a lot because the clear coat is long gone as it's from my parts car. I was never going to cut up my perfect blue hood. Regardless I take good care of my paint (in my opinion) and all of the grime that accumulates just rinses away fairly easily. I built a shroud to hide the ugly hole in the hood, and the flap comes off the bracket with a simple quick-release pin thing.

I also have euro headlights and a 130? amp alternator from a Saab to drive all my electrical junk. The AC runs on "enviro-safe" r134a replacement, incredible stuff. The car is also on H&R lowering springs and on 205/75R14 Tires. It has a great look in my opinion.
2685123
 

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1982 300SD, DM 7.5mm pump, 722.6 AMG trans with OFGear Controller, A/W Intercooler. HX35 planned
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65 Posts
Discussion Starter · #19 ·
Do you have any data on how effective it is? I've always been skeptical of that design.
I don't have any hard data on how good it works. I just know when I was driving to college without it last semester, I couldn't keep the pedal down on the long uphill pulls on the interstate, but now I can and the EGT never gets close to my limit. I also can be on a perfectly flat and straight road with it turned off, and notice EGT temps drop if I flip it on and maintain throttle position. It has a slight "seat of the pants" boost too, but that could be a placebo effect. If I use my thermal camera on it, I can see a temp difference from driving around with it on vs off. Driving around with the system off, the front radiator stays ambient, and the IC gets really hot, but if I have it turned on, the IC gets a lot cooler and the front rad gets warmer. It's doing something I hope
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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You need an IAT gauge! ;)

What do you run for EGT? What's your "limit"? Do you know how much boost it's making?
 
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