I hope somebody here is smarter than I am,and that prolly won't be hard to do! The problem I am having is I changed the tranny,then my speedo is off.By half!! When you are doing 40 it is showing 80 !! I now can't get in touch with the guy I got the trans from to find out what speedo the other car had in it,this one has 80 mph,to know which one I need to get to fix my problem.Do I need a 120 or a 160,or did they ever put a 160 in a 300SD ?? Any help would be great.

To give you an idea, I changed my speedo from 80mph to 120mph. Previous 80mph is off by 5 and the 120 by 10mph as per my GPS.

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So mabye the "other" SD did have a 160 MPH speedo.? That would explain it being off by 50%.

My mechanic says changing the cluster won't affect reading unless you changed your differential with a different ratio. You might want to check other components first. I'm no expert so let's wait for others to share their view.

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With a mechanical speedo that would be correct,but with an electronic speedo I think it all depends on the number of pulses (?) from the transmission to the head. From what I can figure this trans has a different ,I guess you would call it a pulse ring, in the trans.If this one has twice as many or half as many "teeth" on it ,I think, it would cause my problem,but I am not sure!