Greetings- This is my first foray into this website. I have a beautiful 1980 240 DL. B21F. It has approximately 400 thousand miles on it. I have been driving it daily since 1982. Runs like a dream. I have done a fair amount of work on this car over the last 30 years. About 4 months ago I swapped the 4-speed for a 4-speed w/OD. The shop doing the work (a reputable shop that seems pretty sharp on 240s) knew from the get-go that the transmission was not going to synch with the speedometer. The plan was to get the transmission in and address the speedo issue later. The speedo read exactly 10 MPH over my actual speed. I learned to live with this but fully intended to get it right. The speedo is labeled r0,980. The thinking at the shop was that a speedo with a different ratio was needed. Last week the shop swapped out the speedo for a speedo of a different ratio. That didn't work. In fact it was worse. Now the original speedo is back in and it is more erratic and inaccurate than ever. I guess my question is what exactly needs to be done to get the speedometer in my car to read my actual speed? Do I need to swap the rear end to one that matches the 4 speed w/OD transmission? The shop seems a little stumped but is planning on pursuing this to my satisfaction. Any wisdom on this subject would be welcome. Thanks.