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-   -   126 rear in 123? (http://www.peachparts.com/shopforum/diesel-discussion/264122-126-rear-123-a.html)

snookwhaler 10-27-2009 02:30 PM

126 rear in 123?
 
I have read this before and now I cannot find it.

Will a rear end out of a 126 go into a 123? Are there certain years that will or will not fit? Or will it not work at all?

I think I remember somewhere reading that it will work....

H-townbenzoboy 10-27-2009 03:03 PM

If by rear end you mean differential, the answer is yes. Differentials from 1981-1985 W126s will swap into W123s. 2nd generation differentials in the 1986-1991 models won't fit.

Les Jenkins 10-27-2009 04:26 PM

You'll have to swap the axle spacer shims but should otherwise be identical.

oldsinner111 10-27-2009 04:28 PM

Go for a 2:47 rear end from a gasser,and enjoy 37 mpg.

daw_two 10-27-2009 04:39 PM

Quote:

Originally Posted by oldsinner111 (Post 2325689)
Go for a 2:47 rear end from a gasser,and enjoy 37 mpg.

Yeah, I wonder who might have one in a 1981 380SEL....:rolleyes:

:D

snookwhaler 10-27-2009 04:40 PM

Quote:

Originally Posted by oldsinner111 (Post 2325689)
Go for a 2:47 rear end from a gasser,and enjoy 37 mpg.

I find it hard to believe that I could go from 25/27 MPG to 37 MPG by going from a 2:88 to a 2:47? I could see maybe gaining a little like 1 or 2 MPG on a good day. Maybe with a 5 speed and a 3:46 or something?

I'm actually looking for another 2:88 (mine is shot). A 3:07 would be OK too. I just want one that is not "sloppy".

Les Jenkins 10-27-2009 06:15 PM

Quote:

Originally Posted by oldsinner111 (Post 2325689)
Go for a 2:47 rear end from a gasser,and enjoy 37 mpg.

Until you correct the odometer mileage for accuracy.

charmalu 10-27-2009 09:09 PM

You will have to change the tri flange. the 126 uses a larger flex disc.

You will have to determine the friction pre load on the pinion nut before removing it. then when you replace the 126 flange with the 123 flange, you will now have to tighten the pinion nut to the original friction pre load torque setting.

good time to change the pinion seal as well.

here are a couple threads about the pre load.

www.peachparts.com/shopforum/showthread.php?t=233540

www.peachparts.com/shopforum/showthread.php?t=81784

Charlie

Les Jenkins 10-27-2009 09:15 PM

Quote:

Originally Posted by charmalu (Post 2325930)
You will have to change the tri flange. the 126 uses a larger flex disc.

Only on the V8's.

charmalu 10-27-2009 09:16 PM

Quote:

Originally Posted by Les Jenkins (Post 2325938)
Only on the V8's.


so the I-6 uses the same size as a W123?

charlie

Les Jenkins 10-27-2009 09:19 PM

and the diesel.

WDBCB20 10-27-2009 09:25 PM

Quote:

Originally Posted by snookwhaler (Post 2325704)

I'm actually looking for another 2:88 (mine is shot). A 3:07 would be OK too. I just want one that is not "sloppy".

What are the symptoms of yours being "shot"?

Whiskeydan 10-27-2009 09:33 PM

Only W126 diffs up thru 85 will fit.

Also, keep in mind that a lower rpm doesn't mean better mpg. It may now require more thottle (fuel) to maintain the same hwy speed since the engine is now not near it's peak torque rpm curve. MPG may drop. :eek:

BTW, I just happen to have a spare 2.88 and 2.47.

t walgamuth 10-27-2009 10:25 PM

Quote:

Originally Posted by Whiskeydan (Post 2325958)
Only W126 diffs up thru 85 will fit.

Also, keep in mind that a lower rpm doesn't mean better mpg. It may now require more thottle (fuel) to maintain the same hwy speed since the engine is now not near it's peak torque rpm curve. MPG may drop. :eek:

BTW, I just happen to have a spare 2.88 and 2.47.

Not likley in my experience. (sorry to disagree, Dan). In a diesel swapping in a taller diff has always worked well for me.

I am running a 307 diff in my 83 240 with euro 300d motor. With the four speed I got thirty highway regularly. I swapped in my five speed and now get 35 36 regularly running 70 to 75 mph.

I could pull a slightly taller gear...maybe a 288 but taking off is already a bit dicey with the 307 rear end.

(the 307 with the 18% od is about equal to the 247). You'll never get 37 running an automatic imho....unless you run about 50 mph).

daw_two 10-27-2009 10:35 PM

Quote:

Originally Posted by Whiskeydan (Post 2325958)
Only W126 diffs up thru 85 will fit.

Also, keep in mind that a lower rpm doesn't mean better mpg. It may now require more thottle (fuel) to maintain the same hwy speed since the engine is now not near it's peak torque rpm curve. MPG may drop. :eek:

BTW, I just happen to have a spare 2.88 and 2.47.

I might have to drive down there with a truck full of seats and some other stuff.

Sorry for the thread, hijack.


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