I'm not sure if this is the right forum for this.

The speedo does not read right, your going fast than is says. It's a 1983 380SEC that has a motor, tranny and dash from a 1983 300SD W123.
Not sure how to correct this issue.

By changing the Dash, I assume you mean the cluster was changed from the SD. If the Differential is the SEC original, then it is a 2:47 ratio. the SD used a 3:07 81 - 84 and a 2:88 in 85.

The Spedo and Diff are geared together. all MB trannys are 1:1, except for the 5 spd manual with OD.

Look at the Diff. on the lower left corner. scrape off the gunk and some numbers will show. the last 3 are the ratio.

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

There never was an 1983 300SD W123.

Did you mean a 1983 300D W123 ??

Or a 1983 300SD W126 ??



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1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

The guy I got it from said it came out of a 300CD W123 1983, then told me he was wrong it was a 300SD... That's what I have to go on.

Just FYI

A W123 gauge cluster will NOT fit or function in a W126 chassis .

It probably is from a 300SD = W126 chassis.

Here is a list, if you are interested.
US Model Chart to 1946

I think I have an SEC cluster on my bench... it may be geared for 227 though...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!