drhach Posted July 16, 2019 Share Posted July 16, 2019 I'm wondering if anyone could provide some insight in to this. I got this 1962 Lesabre about 1-1/2 years ago. The speedometer didn't work. It wasn't high on the priority list so I didn't really bother with it until this Summer. There was no drive gear in the transmission. I ordered one and installed it. The speedometer worked perfectly for 13.2 miles and then quit. I pulled the gear to check it out and the teethe are almost completely gone. I'm sure not going to order another $100 gear until I can sort this out. The speedometer moved smoothly and I couldn't feely any resistance in the cable. I Also recently had the trans pan cleaned out. he said he didn't find any debris in there. Anyone? Link to comment Share on other sites More sharing options...
old-tank Posted July 16, 2019 Share Posted July 16, 2019 Drive gear or driven gear? Pictures? Link to comment Share on other sites More sharing options...
Barney Eaton Posted July 16, 2019 Share Posted July 16, 2019 Do they look like these? Link to comment Share on other sites More sharing options...
drhach Posted July 17, 2019 Author Share Posted July 17, 2019 (edited) Here are pictures. Obviously after the gear was destroyed. I believe it is the driven gear. Yes, it looked like the ones above. I would imagine the only way to get to the drive gear is to disassemble the transmission. I'm going to try to stick my finger in there and see if I can feel anything on the internal gear. Before I installed this, I turned the speedometer cable with a cordless drill. There was no noise and the needle moved smoothly for the 13 miles that the speedometer worked. Edited July 17, 2019 by drhach added more info (see edit history) Link to comment Share on other sites More sharing options...
JohnD1956 Posted July 17, 2019 Share Posted July 17, 2019 I think some things that could cause this are misalignment in the housing, or binding of the unit, or speedometer cable, or incorrect drive gear in the transmission. Link to comment Share on other sites More sharing options...
old-tank Posted July 17, 2019 Share Posted July 17, 2019 3 hours ago, drhach said: I'm going to try to stick my finger in there and see if I can feel anything on the internal gear. Get a bore scope to look at the drive gear: less than $40 to use with your smart phone. That way you don't have to tear it apart to get the diagnosis and then wait on parts. In the meantime use your gps as a speedometer and odometer and drive it! 1 Link to comment Share on other sites More sharing options...
drhach Posted July 18, 2019 Author Share Posted July 18, 2019 That's a great suggestion. I think harbor freight sells a pretty cheap model. I'm certainly driving it anyway. I just want to get all systems operational. I'm cheap enough and enough of a nerd that I'm looking in to making a speed sensor that would run the speedo cable. Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted July 18, 2019 Share Posted July 18, 2019 2 hours ago, drhach said: That's a great suggestion. I think harbor freight sells a pretty cheap model. I'm certainly driving it anyway. I just want to get all systems operational. I'm cheap enough and enough of a nerd that I'm looking in to making a speed sensor that would run the speedo cable. There is one out there. Ben Link to comment Share on other sites More sharing options...
Build4#2 Posted July 18, 2019 Share Posted July 18, 2019 Gm transmissions use two different size driven gears depending on the rear end ratio. The problem I had with my camaro was I needed a 19 tooth drive gear but my trans had a small diameter driven gear so the teeth didn't mesh hence the Speedo didn't work. It is possible that you have a large diameter driven and drive gear and that caused the teeth to be destroyed? Was it difficult to install the drive gear? Bruce Link to comment Share on other sites More sharing options...
drhach Posted July 18, 2019 Author Share Posted July 18, 2019 There actually are two companies selling speedo cable drivers. Both of them are well over $300. I'm thinking I can make my own for much less than that. I just bought an Arduino controller board for $12, I need to get a DC motor and figure out some way to mount a sensor for a square wave output. I may have bought the wrong size gear. I checked my speed against a GPS and it was pretty good. The repair manual actually has a table telling you what size gear to use based on rear end ratio. I talked to the guy I bought the gear from (bestoffercounts). He suggested a few checks I could do. Mainly validating that the core spins freely and the bushing on the back of the speedo isn't sticking. So that and a bore scope are my next steps. 1 1 Link to comment Share on other sites More sharing options...
Ben Bruce aka First Born Posted July 18, 2019 Share Posted July 18, 2019 Man, if you manage to make one reasonably, I am interested in unit #2. Ben Link to comment Share on other sites More sharing options...
drhach Posted July 18, 2019 Author Share Posted July 18, 2019 (edited) The second one should be a lot easier 😄 Edited July 18, 2019 by drhach (see edit history) 1 Link to comment Share on other sites More sharing options...
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