Two speedometers. Are either correct for the car?
 

A quick question which someone here may have an answer to. The PO mentioned that the odometer wasn't functioning when he bought the car. I replaced parts of the gauge cluster with what I suspect were parts from a late 70's 240D, as he specifically mentioned pulling bits like the good from bumper from the same car.

Here's what concerns me. The speedometer that is installed in the car reads up to 100 MPH. The one with the pile of cluster parts in the back of the car reads up to 110 MPH. I suspect I may see mileage and speed indication issues. Should the '77 300D have the 110 MPH speedometer and matching odometer?

The ones, three, I have read up to 125 mph. My best guess is, yes, ther will be a difference. On speedo's that have the same top speed, there are sometimes different shift points on gauge. I think that indicates a different rear end gear. Something, odo perhaps may be off.

Afik all the 123 240s carried the same gear ratio in the rear end. Since the speedos match the rear ratio the speed indicated going higher seems to me to be irrelevant.

IMHO it should work fine for you.

Tom W

I am pretty sure the automatic 240's would have a different rear gear ratio than the manual trans 240's. also, there is nothing saying that the speedo's in question came from a 240 at all... post pics, including the little part # on the speedo, and perhaps somebody can trace the # to what vehicle it should be in...and the rear gear ratio that should be in there.

Guys, the speedometer probably came from a 240D, but my car is a 300D. That might make a difference, but I'm not sure.

I'll get photos of the gauges and try to find part numbers the next time I'm working on it.

The 300d na carried a 346 rear ratio. The 240s carried a 369 whether automatic or stick. If you have a 300d with the factory rear ratio the speedo from a 240 will work but it will read wrong.

Tom W

I agree, also, I believe the 240D speedos are 100 mph, the 300D N/A speedos are 110 mph, and the 300D turbo speedos are 125 mph (not counting the silly 85 mph U.S. versions).

In other words, the 100 MPH speedometer currently mounted in the car isn't going to read properly. What I need to do is repair the original speedometer. Now my question is, whether the speedometer cable drives both the odometer and speedometer independently, or if one is dependent on the other. There's a chance I could simply swap the good odometer on to the original assembly. I'll do some searching. :)

It does not matter what the display shows, 85mph-100mph-110mph-120mph-761mph. What does matter is what car model and year the speedo came from or more specifically, what rear end ratio it had.

There is no way to convert an existing speedo/odo to read differently. They are tied together through the same drive cable. All you can do is swap it with one from the same model and year range. In your case a 77-81 300D, 77-81 300CD, or 78-80 300TD will work.