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Old 09-29-2009, 03:55 PM
Ian White's Avatar
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 655
Question w123 transmission in a w126?

I want to use my w123 parts car transmission in my w126 300sd, bu my sd has and electronic speedo, whereas the 300d has a mechanical. Is there any way to do this while still having a speedometer? THANKS

Ian White

1995 E300 Diesel w124 OM606
2007 GMC Sierra Classic 1500 4x4 5.3L

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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Old 09-29-2009, 04:57 PM
bsmuwk's Avatar
Join Date: Jan 2009
Location: IL / WI
Posts: 967
Hopefully Paul will chime in here with what he did.

I sold him a good W123 transmission out of an 85 300D. He put it into his 300SD by swapping a few things here and there. Apparently, it's wonderful.
Lakemoor, IL
Artisan Motorenbau
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Old 09-29-2009, 05:07 PM
Graplr's Avatar
Registered User
Join Date: Apr 2007
Location: Sacramento, CA
Posts: 1,594
You will need to swap the tails. Apparently it is a special Mercedes tool. Some on the forum have it and will loan it to you. Someone offered it to me when I was looking to put a 116 tranny into my 126 but ended up just getting a 126 tranny.
2009 ML320 Bluetec

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD
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Old 09-29-2009, 08:56 PM
Ian White's Avatar
Join Date: Jan 2009
Location: Spokane, Washington
Posts: 655
Well, where do you get this special tool?
Ian White

1995 E300 Diesel w124 OM606
2007 GMC Sierra Classic 1500 4x4 5.3L

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)
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Old 09-29-2009, 11:02 PM
pawoSD's Avatar
Join Date: Oct 2004
Location: Grand Rapids, MI
Posts: 15,284
I did this project successfully as was mentioned above.

The "special tool" is only needed for the older (82 and earlier) transmissions as they have a 4-tab locknut on the output flange, and the newer transmissions use a 12 point 30mm socket, easier/cheaper to obtain. Since your SD is an '81 it will need the 4-tab style socket to remove the old nut. The replacement nut will be a 30mm 12point. Also needed will be a rear housing gasket, and a razor blade to get all remnants of the old gasket off the surfaces. The "special tool" can be borrowed possibly, or you can make getting metal pipe in the correct size of the nut, then cutting out the sections with an angle grinder to obtain an end with the 4 tabs that fit in the slots...then a pipe wrench can be used on the pipe to loosen the nut. I found it easier to find/borrow a proper socket....

After the rear output flanges on both units have been removed, the cover is unbolted and removed, then the internal parking prawl/speedo transmitter piece is swapped, with care to keep the original spacers intact and in the right places. The actual swap is pretty easy. Then just set the new gasket in place on the tabs, and tighten all the bolts in an alternating fashion to about 15-20nm.

So far I've driven a little over 2,200 miles with my converted 300D trans and it works great!

A search of the forum will reveal more in depth threads and explanations of the whole process.
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 89k - mine - (OC-91,200)
'17 Metris(VITO!) - 17k - wifes (OC-17k)
'01 E320 Wagon - 160k - mine (OC-160,000)
'01 E320 - 180k - dad's (OC-182,500)
'07 E350 Wagon - 133k - dad's (OC-139,500)
'01 SL500 - 54k - dad's (OC-59,000)
'16 E400 4matic Sedan - 78k - Brothers (OC-80,000)
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Old 09-30-2009, 12:03 AM
DeliveryValve's Avatar
Chairman of my Benz
Join Date: Jun 2006
Location: Central California
Posts: 4,143
Yes do a search.

This is what your swapping out.
1983 123.133 California
- GreaseCar Veg System

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Old 09-30-2009, 07:02 AM
turbobenz's Avatar
Registered User
Join Date: Nov 2007
Location: Cameron Park CA
Posts: 1,869
The old nut is not hard to remove. Usually a chisel and a hammer on the edges can do it. The 12 point nut is horrible though. I tried looking everywhere for a an ultra deep 27mm star socket but eventually welded my own together. The dealer sells them though but their super expensive. Replace the rear seal while your there too and put a thin coat of RTV grey on both sides of your new gasket (and youll have to figure out which gasket to use, idk if you can use the 300d one or the sd one or if you can use either one. Just look at the edges and passages.

1981 300SD 512k OM603

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