Well guys I have what is probably another dumb a$$ ?, but no one around here can answer it for me so I'm going to drop it on you. In my 57 convertable I a running a 302 with a C-4 trans. I have never been able to get the speedometer to work. I had Bob"s speedometer
rebuild the speedometer put it in and it would not register. Sent it back and they told me it worked fine so put it back in and still no go. This was about 15 years ago, I use the tack to tell me about how fast I am going. Now that I have decided to sell the car I need to get it to work. The cable is good and long enough, now for the ? Is the nylon drive gear the same size from a fordomatic as a C-4? Or is the C-4 bigger around and longer. It just dosen't seem like the nylon gear is making contact with the gear in the tail houseing. Hope this makes since, bottom line is the nylon gear the same size for the fordomatic and the C-4. Thanks, Alvin
No idea if the speedo drive gear on the transmission is the same size or not. I suppose the easiest way to see what is happening, is to pull the speedo cable out of the transmission, put some grease or Vasoline on the speedo cable gear, reinstall the cable, and either drive the car a short distance, or with the rear wheels off the ground, put the trans in gear so the rear tires turn several revolutions, and then remove the cable again, and see if the grease on the teeth has been squeezed out, as it should be if the gears are meshing. you can also have somebody watch the speedometer, while you spin the gear by hand, and see if the needle moves . If the gears look like they they are meshing, you can remove the clip and gear from the trans end of the cable, and pull the cable core out of it`s housing, and see if the square end of the cable is intact, broken, or damaged.
You mention the cable is "long enough". I had a problem with a speedo (Toploader 4-speed) where the cable appeared to be a bit too long. If I screwed the cable all the way into the speedo, it wouldn't work. But, if I left it a few threads loose, it worked fine. Not sure if the real issue was that the cable was too long or if there was something else jamming things up. Might be worth trying to see if it makes a difference.
There are RH and LH gears with different tooth counts. If you have the wrong hand in the tranny the cable will spin backwards. This is the case for toploaders and I think that applies to the automatics too. Look at this website, they can help.
http://laspeedometergear.com
QuoteIs the nylon drive gear the same size from a fordomatic as a C-4?
Did you have the speedo cable housing modified to go to a C4? Yes, there are a multitude of driving and driven gears. Do you know the original application of the C4?
The trans was original in a 70 ranchero, with a 351 Clevland. I am sure the nylon gear is right if it wasn't I think the teeth would be chewed up. I will watch the vido when I get back from getting my covid shot, hope it will shed some light on my problem. Thanks for the input, take care, Alvin
If the the transmission was original to a 351 Cleveland it should be an FMX.
In my Quest to get an accurate speedo reading with my 57 T85 od with 4;11 gear which isn't supplied in 57 I've tried several different gears, I believe i need a 22 tooth driven gear. Haven't been able to come up with one. The 57 type gear is smaller in diameter then later gears. I've had luck splicing speedometer housings to use correct end for transmission, Cut both cables to needed length and splice with a compression coupling, don't crush. Cut a universal cable to proper length. I finally gave up on my quest and bought a GPS speedo for around $60. Plug it into a hidden socket and place on dash when needed. Sometimes modern technology is good.
Unless I'm not understanding the question corrector I'm pretty sure a later model trans like yours uses a completely different type gear then the original 57. Did you put in a later model speedo cable and gear to match the trans?
As mentioned, there are right and left hand angled gears for the transmission end of the Speedometer cable. I discovered this by accident in the early 80s, when I swapped 3.50 rear axle ratio in my 70 Mach 1, to 4.30s. Since the 4.30s were a factory optional ratio, I went to my local Ford dealer, and ordered the driven gear for a 4.30 car. Imagine my dismay when the speedo did not work while driving, but it did while backing up. Unbeknown to me at the time, the Mustangs with either 4.30 or 3.91 gear ratios, utilized a gear reduction unit, between the tailhousing and speedo cable, so the tooth angle was opposite. A similar situation occurred with my 59, when I went from the 332 and FordOMatic, to the 428 CJ and Toploader 4 speed. My Toploader has the hole for the speedometer is on the passenger side, so the stock cable was too short to reach. Luckily for me, a buddy had converted his 64 Comet into a drag car, and since his Jerico 4 speed had no provision for a speedometer, he gave me the speedo cable from his car, which had a Toploader, and not only was the length sufficent, the threaded end from the dash end of the cable fit perfectly onto my 59s speedometer. All I had to do was install the correct gear for the transmission end, based on gear ratio and tire diameter.
Jim, Not sure but you may have just answered my ? I used the same cable and drive gear that was in the car,[57] now when you say there is a bigger gear for the newer trans this makes since as, as it seems the cable gear and the gear in the trans do not touch, or touch just slightly. As far as right or left gear rotation I am sure that part is right, as I can feel the teeth on trans gear.
Good way to check if the gear is meshing is pull the cable off the speedometer and try to twist it. Pain to get to but a sure test.
Quote from: Ford Blue blood on 2021-01-29 15:40
Good way to check if the gear is meshing is pull the cable off the speedometer and try to twist it. Pain to get to but a sure test.
I would follow this suggestion first to check if it is turning. We really need a picture of the 57 and a later 60's-early 70's.
You need to have the speedo cable housing modified to use the 57 speedo head and the later drive gear(s).
- https://speedometercablesusa.com/cables_and_housing_assembly.html
Quote from: thomasso on 2021-01-29 11:30
In my Quest to get an accurate speedo reading with my 57 T85 od with 4;11 gear which isn't supplied in 57 I've tried several different gears, I believe i need a 22 tooth driven gear. Haven't been able to come up with one. The 57 type gear is smaller in diameter then later gears. I've had luck splicing speedometer housings to use correct end for transmission, Cut both cables to needed length and splice with a compression coupling, don't crush. Cut a universal cable to proper length. I finally gave up on my quest and bought a GPS speedo for around $60. Plug it into a hidden socket and place on dash when needed. Sometimes modern technology is good.
There are two different drive gears (6 tooth and 7 tooth) for a toploader perhaps those gears will fit. I know its too late in your case but this may help someone else.
I changed the Raunch Wagon from FOM to AOD. Other than tooth count for rear gear ratio, no change was needed. I changed the Custom from OEM three speed manual to C6 to TKO600 with no speedometer cable change. I have a drawer full of speedo gears with different tooth count than will fit almost all left side drive speedometer applications. Most of these gears will interchange right up to the end of mechanical speedometers. There are different gears for right side speedo drives.
If Bob's Speedometer rebuild the speedometer, I doubt the speedometer is the problem. I would test the speedometer and cable by disconnecting the speedo cable at the transmission. The gear has a bearing support on the end which is perfect for chucking into a cordless drill. Lock the drill trigger and go look at the speedometer. If speedo is not working, reverse the drill. If speedo is working, your problem is in the transmission. For some reason, C4s have different tooth counts on the driving gear (output shaft). I've seen a couple of times that due to mix and matching C4 parts would have too much runout in the tailhousing area so the speedo gear had poor engagement.
The transmission end of the speedo cable should be the FORD style like in the previous post PIC.