What's The Difference - PeachParts Mercedes-Benz Forum

Carpenterman · #1 01-01-2010, 09:28 PM

I have a question for all of you wagon masters. I am considering an '85TD as a parts car for my '81TD daily driver. I recall reading that the differential has a different ratio, the speedometer is electronic rather than mechanical, and the transmission is improved in some fashion. Is this correct?

What else of consequence is different? Will the transmission and/or motor swap without hassle?

The owner also said that the motor had been replaced (late '90s?) due to a factory recall. That MB had a recall on this engine is news to me. Didn't the California cars have a trap oxidizer recall? They didn't replace the engine though, did they?

Appreciate any info.

aaa · #2 01-01-2010, 10:53 PM

Interior carpet, hazard switch, no chrome caps in instrument cluster, different tach setup (will you don't have one but you also probably won't be able to use the 85 one), different seatbelts...

Motor swap would be straightforward, you already know about the electronic transmission pickup.

Carpenterman · #3 01-01-2010, 11:17 PM

Thanks for the info. I think they also had electric mirrors, didn't they? Does the differential with new ratio bolt in the same as the older one?

mobetta · #4 01-01-2010, 11:26 PM

diff's are the same aside from the gearing. all the 85 123's ive seen had mechanical speedos. to maintain the correct mph on your dash you will need to swap out the cluster, speedo or gears.
all 123's ive seen drivers side mirrors are manual, passenger side are electric.

the tranny controls are a bit refined, the tach signal is different, the turbo ob an 85 has ARV(?) and the IP has that electric thing on it. but as for engine/trans swap you can do it w/ little issues.

and i am sure i forgot some, and am prolly wrong about something, too.

JimmyL · #5 01-01-2010, 11:54 PM

Quote:

Originally Posted by mobetta

diff's are the same aside from the gearing. all the 85 123's ive seen had mechanical speedos. to maintain the correct mph on your dash you will need to swap out the cluster, speedo or gears.
all 123's ive seen drivers side mirrors are manual, passenger side are electric.

the tranny controls are a bit refined, the tach signal is different, the turbo ob an 85 has ARV(?) and the IP has that electric thing on it. but as for engine/trans swap you can do it w/ little issues.

and i am sure i forgot some, and am prolly wrong about something, too.

There will be plenty of parts to make it worthwhile.
First off, it is the '81 that has the electronic speedo. The only year/model W123 to ever have one.
The IP on the '85 has some type of electronic thing on it, but I don't think it's used for anything. Besides, you very seldom have IP issues anyway.
Tach stuff on '85 is different, but then again an '81 doesn't have a tach anyway. You could sell those parts, especially the end of the wiring harness behind passenger side kick panel. {not real high dollar stuff, but it can help somebody} I would try and plumb in the blue flying saucer from the '85 into the '81 for better shifting.
Mobetta really gave good info!

pawoSD · #6 01-01-2010, 11:57 PM

I put an '85 W123 300D transmission into my '82 W126 300SD 5 months ago and it only required minor modification to make it work. (conversion from mechanical speedo to electronic). It has worked perfectly, even without all the fancy vacuum stuff on an '85. I've put about 5,500 miles on it so far. 81 more every day!