I knew that, after swapping in a J-type M41 for the BW35 my "71 142E came with, the speedometer was pessimistic. The other day I drove it side by side with my 245 - my daughter driving - ,and we found that the 142's speedo showed 56 when the 245's showed 65 mph: and we know the 245's is accurate. That was much more of a discrepancy than I expected. (No wonder I was getting only 20 mpg) The potential, though only partial, solution I can think of so far is the swap the 20 teeth speedometer drive pinion in there now for one with fewer teeth. The smallest number of teeth available is 18. I contacted Duane Hoberg, the OD Guru, and he was kind enough to check his parts bins, but could only come up with a 19 teeth drive pinion. I have contacted two suppliers in the UK who supposedly have the 18 teeth drives - no reply yet. While I wait for them: does anyone have any other solutions? Does anyone have an 18 teeth drive pinion he'd like to sell or swap for 20 teeth -- know of a US supplier? Sure, I could always tape new numbers onto the speedometer face, but that's a bit of a cheat I think. BTW, I running 185/75/R14s at the moment and 195/65/R15s in summer.
Thanks,
Bob S.