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Old 10-30-2009, 06:59 PM
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Join Date: Jan 2009
Location: Manchester,NH
Posts: 392
W123 Transmission swap, how difficult is it

I am looking at buying a 85 W123 300D. The car really looks nice, almost perfect condition with 100K on it. I would like to put in a manual transmission, and need to know how hard that it. can i just throw in a 240D manual transmission, and if I do that how will the car behave with that gearing. Will it have any effects on MPG, or performance. Also, what other parts would need to be changed out, and will this even work. What suggestion do you guys have. Maybe a different transmission(not sure what they put into the 300Ds in germany). Any suggestions would be appreciated.

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Old 10-30-2009, 08:53 PM
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Join Date: Dec 2005
Location: Carson City, NV
Posts: 3,803
There are numerous old threads on this very subject. I'll summarize:

You can use a 240D manual transmission and flywheel. You will need to modify a driveshaft to get the correct length, and the shift linkage will need modification also. It's best to have the donor and recipient cars side by side so you can get everything you need as you need it.

After the swap, expect to gain a little in mpg. Acceleration will be down slightly since you will lose boost while shifting, and the 240D manual transmissions are kind of slow-shifting.
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 367,xxx miles
08 Triumph Street Triple 30,xxx miles, lowered 10mm in front, Pirelli Angel GT tires, EBC HH brake pads, otherwise stock.
88 Jaguar XJS V12 93,xxx miles. I should be in the garage now.
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Old 10-30-2009, 09:21 PM
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Join Date: Dec 2005
Location: Shelton, CT
Posts: 345
With an '85 you have to consider the "pilot bearing issue."
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Old 10-30-2009, 10:16 PM
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Join Date: May 2007
Location: Out in the Boonies of Hot, Dry, Dusty, Windy Nevada
Posts: 9,628
I did this swap to my 85 300D last April. I did replace the engine after the timing chain fail. so the engine I have has a crank pre 85, so the pilot bearing issue wasn`t a problem.

Think the only way around this, is to have a bronz bushing turned to fit. The bearing or bushing just supports the end of the transmission shaft.
My 82 Datsun Diesel Pick Up uses a bushing, and has worked ok for 28 yrs and 456xxx miles. lots of vehicles use one.

with the 4-spd manual trans you will pick up 2 -3 mpg.

here is a thread that was running a week back. post #10 I listed a few threads that should help you.

talk to the people who have done the job, not the na-sayers.


there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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