markfh
Well-Known Member
I'm thinking it's the gear in the 727 transmission but what else might be the problem.
Thanks...
Thanks...
68 GTS Speedometer doesn't work
- Thread starter markfh
- Start date
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The car is not moving?
Not a lot of info to go on.
What have you done to the car lately?
Did the spedo ever work correctly?
As for testing the easiest would be to pull the speedo cable from the trans and look at the cable insert. you might be able to hook it to a drill motor and spin it to see if the speedo moves. Try spinning the cable counter clockwise but be careful you do not pull the inner cable out from the speedo head in the process.
Not a lot of info to go on.
What have you done to the car lately?
Did the spedo ever work correctly?
As for testing the easiest would be to pull the speedo cable from the trans and look at the cable insert. you might be able to hook it to a drill motor and spin it to see if the speedo moves. Try spinning the cable counter clockwise but be careful you do not pull the inner cable out from the speedo head in the process.
Demonic
Well-Known Member
More likely the cable than the gear, the gear is pretty tough and simple. Set the rear axle securely on stands, disconnect the cable at the speedo and idle in gear - see if the cable end spins. Or like Dana67 said, do the drill trick, a bit easier.
markfh
Well-Known Member
I've done a lot.
Rebuilt or restored (not all me)
1. Steering Box
2. Carburetor
3. Power Steering Booster
4. All new brake lines and brakes
5. Re-gasket the upper end of the engine
6. A little here and a little there
At one time the speedometer did work but the car had been on jack stands for 28 years. I had the transmission rebuilt about 3 years ago and that's when it stopped working.
I'll try taking the cable out of the transmission and do the drill test.
When you say "do not pull the inner cable out from the speedo head" are you talking the end of the cable at the transmission?
Thanks...
Mark
Rebuilt or restored (not all me)
1. Steering Box
2. Carburetor
3. Power Steering Booster
4. All new brake lines and brakes
5. Re-gasket the upper end of the engine
6. A little here and a little there
At one time the speedometer did work but the car had been on jack stands for 28 years. I had the transmission rebuilt about 3 years ago and that's when it stopped working.
I'll try taking the cable out of the transmission and do the drill test.
When you say "do not pull the inner cable out from the speedo head" are you talking the end of the cable at the transmission?
Thanks...
Mark
Lord Sparky
Well-Known Member
A speedo shop can fix the insides—very delicate. Mine went bad. I bought a brand new one from 1977. I still needed to get it serviced as the lube dries out.
furyus2
Well-Known Member
When you say it didn't work after the trans was rebuilt, i wonder if the speedometer gear holder, or whatever it is called, is not clocked properly. Look at where the speedometer cable attaches to the transmission. You will see a larger holder, adapter thing that the cable screws into. Take out the 7/16 head bolt out. Pull out the adapter. You will see the gear. They are numbered. If it is, for example, a 36,you can put the adapter back in the transmission. There's numbers on the adapter that you would have to rotate the adapter so the line for the number of teeth you have, lines up.
That's where I was going, and the rebuild and it stopped working at the same time really points me in that direction.
The way the transmission speedo adaptor works the following way.
There is a shaft in the trans with a worm gear on it. The speedo gear mates up to it. If the speedo gear has a lot of teeth, say 38, the diameter of the gear will be large. Now say you have a 26 tooth gear. It will be smaller diameter. If the centerline of both gears stays the same, the small gear will not touch the worm gear. The speedo gear is not centered in the adaptor, that way you can rotate the adaptor to move the center of the speedo gear, closer or farther from the worm gear. What Furyus2 was talking about is that the adaptor might be (as an the example) in the 38 tooth position but have a 26 tooth gear. In that condition the smaller gear would not be touching the worm gear in the trans.
(BTW if you do have your gear out for any reason get its tooth count and record it for later use, with that, a speedometer reading and a GPS reading you can determine what gear you would need if let's say you changed your rear gear ratio or rear tire size or both)
The outer cable is screwed (or later years snapped) into the speedo head and trans adaptor. Inside the outer cable is the coiled cable that actually rotates when the output shaft of the transmission rotates. The inner cable typically can be pulled out of the outer cable, (I have exp with some old Ford's that the inner is not retained by anything so you can pull it out from either end of the outer cable) if you pull the inner cable out an inch or so it will no longer be engaged in the speedo. Not to worry, usually you can get it back in without removing the outer cable.
markfh
Well-Known Member
Okay, back from honeydo's. One more question before I get under the car again later today. Can or does this cable get lubrication?
Take the speedometer cable & case out of the vehicle. Determine which end the cable will come out of, only works one way IIRC. Clean the cable with carb or brake cleaner. Clean the cable housing the same way & let them dry completely. Soak the cable in clean 20 - 30 weight oil & reinsert. Check the speedometer gear for tooth count & make sure the insert is aligned correctly & reinstall the cable & casing.
I would not recommend removing the outer cable / case from the car. I have heard horror stories about getting it in and out.
If you really want to remove the inner cable and it comes out from the speedo end you can pull it into the car. You can also clean the insides of the outer case/ cable with spray cleaner and a straw like comes on wd40 bottles, ( Overly protect everything from overspray) And spray from inside the car to the trans with the trans end disconnected of course
The cable & case can be taken out if done carefully. Spraying any cleaner into the case can lead to leakage because the casing is not lined, it's a flexible type of tubing. I've done this many times & have never had a problem. As with any car or part as old as some of our cars & parts, "careful" is the operative word
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