I changed the rear in the 300D from the stock 3.47 to a 3.07. Now I am interested in setting up the speedo to read correctly. What gear do I need to change at the back of the transmission to correct the speedo error? Is is just a matter of changing out the nylon gear that drives the speedo cable?
tia

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Jim

Went for a test drive this morning and it looks like the speedo is showing about 9 mph slower than what you are actually going. The characteristics of the car are more in line with what I am looking for and I am pleased with the change.

edit - got the oldest boy to ride along beside me. The error is more than I initially thought.

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Jim

Just change the speedo.

It's not very difficult to alter the odometer to match your current speedo.

There are specialty shops that will calibrate your speedo. I can find one here in Ca, but that wont help you unless they can figure out long distance calibration.

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Chris
84 280sl
82 300d euro

How do you know if you 300d has the 3.47 or the 3.07 ???

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1985 300D : the clean one 180k miles - Now passed onto my parents.
2000 E39 M5
2002 e46 330xit
1991 mustang notch (project)
1970 chevelle (project)

Your 85's will have a 2.88. It's stamped on one of the lower rear corners of the differential.

all turbo 617s up til 85 have the 307. non turbo is 346. us and euro.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

The differential I pulled out was stamped 3.47. I suspect the fuel mileage is going to be substantially improved.

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Jim

I've just gone to speedometer shops in the past and they've provided me with the correct gear.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

That will correct the odometer inaccuracy but the speedo needle is driven by magnetic drag from a drum turned by the cable.

Why wouldn't the change of a gear at the tranny, change the speed of the spinning cable and hence the magnetic drag on the speedo?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

the only way i have experience with is changing the speedo. i havent done it for seven or so but i got them from the benz store.

reasonably priced.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I thought you meant changing a gear inside the speedo.

I just as soon resolve it at the transmission end.

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Jim

Normal cars like general motors you just change the transmission speedometer output gear to match. It is sounding like mercedes has only one output gear for all these transmisssions. They depend on modification of the head to correspond.
Must be so as most people have claimed if you take the head from a car with the same donar rear end ratio it works properly.
Strange system rather than having various gears for the transmission. Each head will then have a different part number to correspond to the rear axel ratio it is set up for. Or the dealers would have gone insane when these cars where fairly new.