Speedometer swap question - different max speeds - PeachParts Mercedes-Benz Forum

cornblatt · #1 04-30-2004, 12:26 PM

I have a 190D-2.2, and I'm considering replacing the speedometer with one from a 190E.

My current speedometer goes up to 110mph (180km/h).
The potential replacement I'm looking at goes up to 240km/h (140mph). I think it's from a 190E-2.6.

If I swap the speedometer to one with a different speed range, will it still read correctly?

I did a search, and found one post that says the speedometers are dependent upon the rear axle ratio if they are to read correctly. Another post says that the gearing is within the speedometer itself and the speed reading remains correct after a swap like this. Which one is right?

The two posts are below...
http://www.peachparts.com/shopforum/diesel-discussion/78784-different-speedos.html#post500076
http://www.peachparts.com/shopforum/mercedes-benz-performance-paddock/37013-question-about-speedometers-190es.html#post226336

Duke2.6 · #2 04-30-2004, 07:22 PM

Not sure about Mercedes, but GM speedometer heads are all calibrated to read so many MPH per 1000 RPM of cable speed (can't remember the exact number). Axle and tire variables are handled by the speedo gearing in the transmission and can be changed by swapping the externally removable driven gear.

Mercedes probably uses a similar algorithm, and your best bet would be to contact a local speedometer shop or contact your local dealer and ask them for a referal to the speedo shop they use. A speedo shop that does work for a Mercedes dealer should know the answer, or be able to tell you what needs to be done to make the new speedometer accurate for your application.

Duke

cornblatt · #3 06-01-2004, 05:15 PM

I did some more research, and e-mailed some German eBay sellers to ask about the speedometers they had for sale. The information I discovered led me to believe that the speedometer reading is based on driveshaft RPM, which is dependent on the rear axle ratio, so your replacement speedometer must be from a car with the same rear axle ratio.

I found a German website with a table showing the different rear axle ratios that were offered in the 190. There were many more than I thought there would be. I translated the table to english and a copy is attached... If anyone else is looking for the information on which differential was in which car, you can refer to this table.

Stevo · #4 11-30-2004, 05:17 PM

"I found a German website with a table showing the different rear axle ratios "

cornblatt

Could you post that site? I know several people, including myself, that would like that information about the W123s. I have a 280 speedo (I think) in my euro 240D that goes to 150 mph, but it seems very close to "right on"

lino · #5 11-30-2004, 05:38 PM

Please post a link to the site. My research up until this point has lead me to believe that I can use any speedometer for my 1989 300ce if it comes from a car with the M103 engine.

cornblatt · #6 11-30-2004, 06:58 PM

Before I say any more, I should mention that the information I found pertains to the early W201 series with mechanical speedometers (i.e. with a speedometer cable running up to the instrument cluster), and things may be different for the 123 series, or for newer cars (late-80s and newer) with electronic speedometers.

The website with the rear axle ratios (and much more info) was: http://www.baureihe201.de/W201/ It's a W201 site, so it may not help out people with W123s...

I e-mailed a friendly German ebay seller about a W201 speedometer he was selling. He said he bought it for his 190D, but when he put it in the car, it didn't read the correct speed. If he went 125 km/h, the speedometer only said 90km/h. His original was a 201-542-85-06 (180km/h max), and he tried out a 201-542-14-06 (also 180km/h max). He went to the dealer and bought a new one (same part as his original) and that one worked fine.

So, he tried doing a swap to another speedometer and it didn't work. And it wasn't even a different-max-speed speedometer - it had the same maximum speed and it still didn't work!

He recommended that I not buy the part from him because he thought I'd have a similar problem (it's nice to find someone honest!).

So, maybe things are different for the 123s, and things are probably also different for newer cars with electronic speedometers (does the 1989 300ce mentioned earlier have an electronic speedometer?)

I found 13 different versions of the W201 metric speedometer on eBay, and in the end I had no idea which one to get. I gave up on making this swap because I couldn't find a reliable source of information, and I didn't want to do it unless I knew it would work (shipping from Germany is expensive!).