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  #1  
Old 06-19-2008, 08:57 AM
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new rear end gear in a 87 300 sdl

I have a 1987 300 sdl and I'm looking to put a tall rear end gear in to lower the rpm's. I run it on the highway 75% of the time and I'm turning about 3000 rpm's at 70 mph. I do get about 30 mpg though but I believe that would improve with a different gear. Any idea's would be helpful.

Mike
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  #2  
Old 06-19-2008, 09:17 AM
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I'd be really interested in what you find if you make that mod. I've been mulling the same possibility to save fuel and I believe the engine should be fine turning about 2600 rpm at 70 mph.

One of the V8 gassers of that vintage should have the 2.47 for that swap.
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  #3  
Old 06-19-2008, 09:19 AM
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That has the 287 rear end right?

The 300d of that era with the five also carries a 2.65 rear IIRC which would be some improvment.

I am with Brian though I'd probably go for the 247 or even a 224 from a euro if I could find one with the price of fuel these days!

Tom W
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Old 06-19-2008, 09:34 AM
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Quote:
Originally Posted by t walgamuth View Post
The 300d of that era with the five also carries a 2.65 rear IIRC which would be some improvment.
I'm not aware that a diff from a W124 would fit a W-126??
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  #5  
Old 06-19-2008, 11:58 AM
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Rear mounts are different but maybe it's just a matter of chaning the rear cover.

I don't remember the top mounts of a 126 diff.

Sixto
87 300D
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  #6  
Old 06-19-2008, 01:14 PM
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Quote:
Originally Posted by Brian Carlton View Post
I'm not aware that a diff from a W124 would fit a W-126??
I think the later v8s have a bigger diff but I suspect (don't know) that the 124s would be very very similar.

Tom W
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  #7  
Old 06-19-2008, 05:02 PM
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V-8s have a 1.3L case, vice the inlines with a 1L case. I'd bet that if you had all the stuff, they would interchange.

W126 is similar to W123, is similar to R107, W124 is similar to W201, and never the 'twain shall meet. Different mounting style.

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  #8  
Old 06-19-2008, 07:52 PM
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The gears interchange inside the cases between the 124/190 and the 123/126 early, I believe.

So I guess it adds a level of complexity.

Tom W
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  #9  
Old 06-19-2008, 09:45 PM
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I've been meaning to do this for the longest time. Just the cost of No 2 has me rarely driving my Diesel vehicles at this point.
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I'm not a doctor, but I'll have a look.

'85 300SD 243k
'87 300SDL 251k
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'91 560SEL 183k

Eight others from IH, BMW, GM, Ford, and Volvo.

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Old 06-19-2008, 11:35 PM
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A W126 is a W126 those are the parts that will fit. If you want your ABS to work you need the rear end from a 1986+ W126.

Just find a 560SEL in a junk yard and steal the rear end, I think its a 2.47. Plus its a limited slip which is nice to have.

Report back on how it runs up hills.
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  #11  
Old 06-20-2008, 12:09 AM
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Quote:
Originally Posted by Hatterasguy View Post
A W126 is a W126 those are the parts that will fit. If you want your ABS to work you need the rear end from a 1986+ W126.

Just find a 560SEL in a junk yard and steal the rear end, I think its a 2.47. Plus its a limited slip which is nice to have.

Report back on how it runs up hills.


Well only 86+ fit the 86+ as the subframe out back changed.

I'm on the lookout for a 2.47:1 for my 300SD with ABS, so it'll be from an '85 500SEL
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'85 300SD 243k
'87 300SDL 251k
'90 300SEL 322k
'91 560SEL 183k

Eight others from IH, BMW, GM, Ford, and Volvo.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
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