I recently purchased a new (to me) 1980 240d 4spd. The PO told me the speedo reads 10 mph off. The part # on the speedo is 123 542 62 01 and it goes up to 85 mph. Can anybody tell me if this is the correct part# for my car? I suspect the error is from someone in the past swapping in a speedo from something with a different rear end ratio, maybe a NA 300d.

Your number for the spedo is the same as my 80 240D.
the spedo starts at 10 mph, if that is what the po is refering to.
use a GPS to get the exact reading on MPH.

Your Differential should be a 3:69. looking at the rear cover of the diff., the
ratio is stamped on the lower left corner of the diff case. scrape off the dirt
and grease and a set of # will reveal them selves. should be the last #.

with a GPS I found out my 300D is off 10mph at the higher speeds. the lower
speeds it seems to be more acurate.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Yes, unlike American cars the speedometer head itself is calibrated for the rear axle ratio. Use Charlies instructions for finding axle ratio and then google up for a speedo vendor.

Let me know what speedo you need and I might be willing to part with the one from my parts car for whatever the going price might be.

Thanks for your advice, guys-- now after a couple minutes under the car with my trusty pocketknife I know what the problem is-- I have the 3.07 gear!

I thought this thing was slow, but since I have always had 5cylinders, I thought its' lack of get up and go was normal for a 240.

Soooo, next question-- what is the right part# for the 300d turbo speedometer, as apparently thats what I need?

WOW a 3.07 in a 240? um, I'd swap that out asap.
lemme know if you need a 3.69 or a 3.47 with matching odo/speedo.

The 3:07 Differential was used from 82 to 84, so I suppose any of those could be used.

I just checked my list of spedo`s I have.
83 300D - 123 542 18 57

84 300d - 123 542 28 57

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Yes, i will probably have to swap it out-- I have an extra 3.47 diff, that should work ok with the 4 spd.

Thanks for the numbers, I will see if I have one of those in my parts pile, maybe swap it in 'til I get the diff changed out--would be nice to know how fast i am going.

'82 300D - 123 542 85 01 - 85mph speedo with silver center button.

The other two above are 120 mph speedos with black center button

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1983 123.133 California
- GreaseCar Veg System

Maybe your car has tires that are not factory size. Only takes a couple minutes to check. Different size can change speedo reading.
Try this site to check the percentage & mph difference.
www.miata.net/garage/tirecalcold.html

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1984 MB 300SD Turbo

Thanks, I thought of that but my tires are correct. It is the 3.07 diff that is giving me the trouble, as it turns out.