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  #1  
Old 06-25-2016, 11:38 AM
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240d /300d diff swap

How easy is it to swap the diff in a 240d to a 300d. I have the 4spd manual transmission and would love to be able to cruise on the highway at a lower rpm. Is It a matter of unbolting and bolting a new one on? Or am I going to have to change the drive shaft?


I know I will have to pull the spedo from the 300.

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  #2  
Old 06-25-2016, 12:48 PM
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No it is a really easy switch, the axle shafts have to come out of the differential and there are two different ways Mercedes attaches the shafts, One unbolts from a hub the protrudes from the differential, the other type goes into the differential and is held there by a "c" clip. But outside of that, it is just a case of unbolting it from the body. It is a bit heavy and typically a bit greasy. You will probably want both cases drained of oil before you start. Make sure the filler plug which is higher up on the case is free to open. Some of them are terribly difficult to open if they have been closed for the past 25 years. Also, the ratio of the gearing in the differential is stamped on the case. Don't over gear it or you will have to use 3rd gear in a headwind.
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1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

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  #3  
Old 06-25-2016, 06:15 PM
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What gear ratio are you thinking about going to?

300D NA is 3:46
300D Turbo 82 - 84 3:07
300D Turbo 85 2:88

Your 240D uses a 3:69

Change the Differential to a different ratio, then you will need to change the speedometer
from the vehicle you acquired the diff.
The Spedo`s are geared to the differential.

Iam using a 3:58 out of a 280E. It`s a 3% decrease in RPM`s.

Charlie
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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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  #4  
Old 06-25-2016, 06:37 PM
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Keep the 240 rear cover... its got better cooling fins.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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Old 06-26-2016, 07:12 AM
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I was able to swap the rear diff in my 83 240D without removing axles. There is enough articulation in the CV joints to rotate at an angle at the wheel side and plunge in at the diff side.

I hear there are two different types of axles.

One that looks like these: (Portal?)


And one type where you cannot remove them without opening the diff.

I am however now stuck with a diff sitting on my floor with axles still attached and the bolts that hold them on secured with no way to easily loosen them. If you have the type pictured above and you're planning to take the axles off the diff loosen the bolts while its still mounted in the car.
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  #6  
Old 06-26-2016, 10:15 AM
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Quote:
Originally Posted by BirthdayBenz View Post
I was able to swap the rear diff in my 83 240D without removing axles. There is enough articulation in the CV joints to rotate at an angle at the wheel side and plunge in at the diff side.

I hear there are two different types of axles.

One that looks like these: (Portal?)


Or have QUALITY XZN tool, and an impact wrench... or, just open the diff and pull the clips... easy.

And one type where you cannot remove them without opening the diff.

I am however now stuck with a diff sitting on my floor with axles still attached and the bolts that hold them on secured with no way to easily loosen them. If you have the type pictured above and you're planning to take the axles off the diff loosen the bolts while its still mounted in the car.
Nahh... just get QUALITY XZN tools and an impact wrench... or simply open the diff and pull the clips holding the axles in...

Easy.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #7  
Old 06-26-2016, 11:44 PM
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Posts: 311
Quote:
Originally Posted by charmalu View Post
What gear ratio are you thinking about going to?

300D NA is 3:46
300D Turbo 82 - 84 3:07
300D Turbo 85 2:88

Your 240D uses a 3:69

Change the Differential to a different ratio, then you will need to change the speedometer
from the vehicle you acquired the diff.
The Spedo`s are geared to the differential.

Iam using a 3:58 out of a 280E. It`s a 3% decrease in RPM`s.

Charlie
either the 3.07 or 2.88. I have the 4 spd manual and do some decent highway driving. Would love to have lower rpm's at around 65/70 mph. I can get up to ~ 80 MPH on a flat.. after that.. the car sounds like it will explode.

Not sure which one will make more sense... the 3.07 or 2.88. I just sent my spedo and cruise unit to JamesDean for a repair.... either way.. i will make sure to get the new spedo when i do this job. Just waiting for a junkyard to have what i want.


So do you recommend removing the axels from the other car first and then removing the diff? And then on my car... removing the axels then the diff.. then put the new diff in and reattach the axels? I have heard conflicting information regarding if you can do the diff swap without removing axels.
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  #8  
Old 06-27-2016, 11:15 AM
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Join Date: May 2007
Location: Out in the Boonies of Hot, Dry, Dusty, Windy Nevada
Posts: 9,653
I know the thinking of going to a higher gear ratio will give me better mileage,
But if you go to a too high of a ratio, you could shoot your self in the foot and get less mileage.
The 240 engine (depending on year) has 60 something HP, and will be struggling to keep going.

There is one guy in Kansas that put a 3:07 in his 240, but Kansas is relatively flat.

With my 3:58 I didn`t notice any power issues, but I do get better mileage. I can click along with 35 - 37 on the High Ways.
and 30 - 33 in town. and that all depends on how I drive and weather, traffic etc...


Charlie
__________________
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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  #9  
Old 06-28-2016, 03:39 PM
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Join Date: Oct 2012
Posts: 5,924
Make sure your 240d engine is in good condition. You will want every horsepower those engines where designed to produce. Many simple things not up to scratch can lower their original power output.

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