I have learned a lot while trying to repair my odometer it was previously repaired by benz bin about 3-4 years ago I swapped my old one out and got a replacement and I think they used a gear made of inferior material in that it only lasted this long. What I also want to caution any one else doing this is if you do take the needle and face off be very careful when prying up on the needle because mine went flying and after 8 hrs. of looking for it in my living room I have given up. The 85 300sd signal is all electric and has 2.88 rear compared to the earlier ones 3.07 rear which would throw you milage off also your size wheel could throw it off also as I have the 86 (15") wheels on mine but my milage and speed were close enough if not right on. I did try to purchase a gear from gizmos for $2.36 which is about what it should cost and found out yes they are out of stock on that gear which has 12 and 48 teeth. I refuse to pay $25 for that little gear and instead am looking for a used whole speedometer from a salvage yard. I will let everyone know how it turns out. It is very simple to get at the main drive gears on the 85's I would not have had to take the needle and face off but I did not know this when I started. Thanks for all the replies hope to get this working soon.