Differential Swap

[DeliveryValve]

Hey All,

If you seen the post of my differential having "foam" inside the differential housing, I am begining to hear whining noise that sounds to me like a souped up american V-8 with a gear drive for a timing chain or one with supercharger.

Anycase, I found a donor 1984 300SD with 3.07 gears that I can get the differential out of it. I think this would fit in my 1983 300D but wanted to ask you guys for certain that it would. Would I just swap/install it and use my 300D's axles and spacer?

Thanks for your input.

[TheDon]

I want to say the dif will not bolt up to the W123 subframe but the internals (the pumpkin as I know it) will transfer IIRC

It will work. You just need to change the axle shims.

[DeliveryValve]

Originally Posted by ForcedInduction

It will work. You just need to change the axle shims.

Change it out to what? Do I use the original shim that I took off from the 300d?

I believe so. I know that some people here have used 126 differentials on their 123. Hopefully one can chime in and say exactly what needs to be changed.

[JackG]

If interested, I have a 2:88 differential out of an 85 300D.

[DeliveryValve]

Originally Posted by JackG

If interested, I have a 2:88 differential out of an 85 300D.

No, I don't want to go through finding another speedo to make it happen. Thanks for offering!

[Ken300D]

The MB differentials of this era are well known to whine.

There's a good chance you could put in a lot of effort to change to another used differential, only to find out it whines louder.



Ken300D

[JackG]

Originally Posted by rmarzan

No, I don't want to go through finding another speedo to make it happen. Thanks for offering!

I got that too . 187k on the clock. I have it scheduled for ebay next week.

[Brian Carlton]

Originally Posted by rmarzan

No, I don't want to go through finding another speedo to make it happen. Thanks for offering!

You ought to rethink this.

The 2.88 gets the 617 down to a much more comfortable rpm at 70 mph. Also, the fuel economy with the 2.88 is improved by a few percent. It's defiinitely the preferred diff for the vehicle.......unless you choose the much taller 2.47.

I had the exact same issue with the pinion whine and switched the SD to a 2.88 and can't be more satisfied with it. It is limited on its hill climbing capabilites, however..........65 mph is about it on most decent grades.

Get the complete setup from Jack. It's definitely worth the additional cost and the fuel savings over time will pay for the cost of the parts.

[85chedeng300D]

is the 2.47 useable on an '85 300D turbo w123 which right now has a 2.88? i live in alabama, the roads are hilly, but the grades are not as steep as in the rockys. i would love to cruise 70 mph on the freeway @ 2000 rpms. but is it going to affect the acceleration from dead stop?

[TheDon]

I havent noticed a whine on my 85.. or Maybe I'm just thinking its road noise.

Surf n Turf has his 240D with the 617 in it and the OG 240D rear end( but is putting in the one from the 300)..

Its fast off the line but the top end sucks

[Brian Carlton]

Originally Posted by 85chedeng300D

is the 2.47 useable on an '85 300D turbo w123 which right now has a 2.88? i live in alabama, the roads are hilly, but the grades are not as steep as in the rockys. i would love to cruise 70 mph on the freeway @ 2000 rpms. but is it going to affect the acceleration from dead stop?

IMHO, the 2.47 is only good for areas that are dead flat. Any hills whatsoever will necessitate a drop to 3rd gear and operation at 3600 rpm at 70 mph. You'll need to do this manually. If it doesn't bother you, then you might consider it. Acceleration from a dead stop is definitely affected in a negative manner with the 2.47. If you're a person who has to contend with any stoplight wars, then it's a no go.

[MTUpower]

Originally Posted by Brian Carlton

IMHO, the 2.47 is only good for areas that are dead flat. Any hills whatsoever will necessitate a drop to 3rd gear and operation at 3600 rpm at 70 mph. You'll need to do this manually. If it doesn't bother you, then you might consider it. Acceleration from a dead stop is definitely affected in a negative manner with the 2.47. If you're a person who has to contend with any stoplight wars, then it's a no go.

Is it difficult to install the w126 diff's in a w123? What needs to be done? Thanks... because florida is dead flat...

[DeliveryValve]

Well there is a saying back more then 10 years ago when I was an undergrad in college. You first get your BS, which is Bull Sh#%. Then you decide to take the next step and get your MS which is More Sh#%. And finally you make that life decision and get your Ph.D., which is Piled High and Deeper.

Well I am past the BS and MS, and now I am working on the Ph. D (not for real but at least on this project.). I looked at the housing numbers and they matched between the two cars. 123 351 0101. I didn’t match the gear numbers but I took peek at inside the 300SD and it is 123 353 0112 3.07. So while all of you were posting on this thread, I was busy removing this pumpkin from the SD. Now I own it and I am in it deeper! In the next month I will find out if this can be accomplished! Stay tuned!

Originally Posted by Brian Carlton

You ought to rethink this.

The 2.88 gets the 617 down to a much more comfortable rpm at 70 mph. Also, the fuel economy with the 2.88 is improved by a few percent.....

I did think about it and would love the gas mileage. In addition to the speedo calibration, the other problem is when I take my regular business trip down to Los Angeles, there is a tall hill called the "Grape Vine" that kills the 300D. I need all the climbling power I can get!