Speedometer Problem
Thread Starter
Intermediate
Joined: Aug 2023
Posts: 25
Likes: 27
From: Virginia
Speedometer Problem
1974 with 3 speed automatic. The original cable was obviously bad so I replaced with a 2 piece cable. When spinning the speedometer end of the cable by hand, the needle moves. Before attaching the other end, I pulled the housing and checked the gear (it was fine). The other end of the cable that plugs into the transmission will not move by hand (so I guess the nylon gear is not spinning against a stripped metal gear. Any thoughts for what to check next? I am flummoxed.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Two piece cable? So you are using Cruise Control? Or do you mean a inner cable and sheath?
There are two gears inside the tranny, both plastic or nylon. One is a "driven" gear and the other a "drive" gear. You will not be able to spin the driven because its engaged to the drive gear. The drive gear is mounted on the output shaft to the driveshaft.
Never hook up an electric drill to the speedometer end of the cable. You will damage the transmission end. You can hook up a drill to the tranny end to check for speedometer needle movement. Which you did.
If you are running cruise, good chance the internals of the transducer are compromised.
There are two gears inside the tranny, both plastic or nylon. One is a "driven" gear and the other a "drive" gear. You will not be able to spin the driven because its engaged to the drive gear. The drive gear is mounted on the output shaft to the driveshaft.
Never hook up an electric drill to the speedometer end of the cable. You will damage the transmission end. You can hook up a drill to the tranny end to check for speedometer needle movement. Which you did.
If you are running cruise, good chance the internals of the transducer are compromised.
Thread Starter
Intermediate
Joined: Aug 2023
Posts: 25
Likes: 27
From: Virginia
Yes, a two piece cable without cruise control. That was what was on the car. When it did not work after installation, I detached the coupler in the middle of the cable and only spun the cable on the speedometer side by hand-no drill. The needle moved. I tried to spin the gear side of the cable by hand, but it did not move which is why I don’t think either the drive gear or the driven gear is stripped. The only thing I did not do is engage the transmission and see if the cable is turning where the cable joins in the middle while detached.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Sounds like at one point there was cruise on this car? Or someone bought the wrong cable. And it sounds like somebody joined the two with a coupler instead of buying the correct cable. Perhaps they didn't want to crawl under the dash and wrestle with the speedo connection. (not fun)
I did away with C.C. and bought a single long cable.
There are several choices of cables.
4 speed w/ cruise (2, upper & lower)
4 speed w/o cruise
Auto w/ cruise (2-upper & lower)
Auto w/o cruise.
You only need a single cable. It will be part listed as a lot longer instead of two short ones for cruise. No need for any coupler.
I did away with C.C. and bought a single long cable.
There are several choices of cables.
4 speed w/ cruise (2, upper & lower)
4 speed w/o cruise
Auto w/ cruise (2-upper & lower)
Auto w/o cruise.
You only need a single cable. It will be part listed as a lot longer instead of two short ones for cruise. No need for any coupler.
Last edited by HeadsU.P.; Nov 26, 2023 at 09:11 AM.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 8,893
Likes: 4,074
From: US-PNW
Sounds like at one point there was cruise on this car? Or someone bought the wrong cable. And it sounds like somebody joined the two with a coupler instead of buying the correct cable.
... You only need a single cable. It will be part listed as a lot longer instead of two short ones for cruise. No need for any coupler.
... You only need a single cable. It will be part listed as a lot longer instead of two short ones for cruise. No need for any coupler.
Here's the '72 AIM showing its installation:
Pro
Joined: Jun 2005
Posts: 703
Likes: 153
From: Central FL
St. Jude Donor '06 thru'17, '23-'26
Can't help you, but i have the exact same problem, but mine is a 4 speed.
Disconnect at trans and turn cable by hand and speedo works.
Disconnect drive shaft and with it in neutral turn output shaft and speedo gear turns.
Hook up cable at trans and disconnet at upper lower cable connection and turn trans output shaft and opposite end of cable is rotating.
Make all connections and turn trans output shaft and speedo does not work.
Take it for a drive assuming I'm not turning output shaft fast enough, still nothing.
At this point, thinking of just putting a one piece cable in and seeing if that works.
Disconnect at trans and turn cable by hand and speedo works.
Disconnect drive shaft and with it in neutral turn output shaft and speedo gear turns.
Hook up cable at trans and disconnet at upper lower cable connection and turn trans output shaft and opposite end of cable is rotating.
Make all connections and turn trans output shaft and speedo does not work.
Take it for a drive assuming I'm not turning output shaft fast enough, still nothing.
At this point, thinking of just putting a one piece cable in and seeing if that works.
Racer
Joined: Mar 2014
Posts: 316
Likes: 36
From: Machesney Park IL
Just tossing a thought out…
I fought my 78 auto with about the same results for almost a week, off n on. Turned out the drive gear in the tranny had slipped down some. Looked ok, since I did not know exactly what I was looking for. I guess at a slow turn by hand, it was ok. At speed, it missed the teeth to turn.
C
I fought my 78 auto with about the same results for almost a week, off n on. Turned out the drive gear in the tranny had slipped down some. Looked ok, since I did not know exactly what I was looking for. I guess at a slow turn by hand, it was ok. At speed, it missed the teeth to turn.
C
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Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
You mean the driven gear dropped down? Which is fairly easy to remove.
The drive gear is clipped on to the output shaft and requires driveshaft removal, tail-shaft housing removal, bracing the trans mount, etc, etc.
If that steel clip on the drive gear ever broke off, then . . . . . . . .
The drive gear is clipped on to the output shaft and requires driveshaft removal, tail-shaft housing removal, bracing the trans mount, etc, etc.
If that steel clip on the drive gear ever broke off, then . . . . . . . .
Racer
Joined: Mar 2014
Posts: 316
Likes: 36
From: Machesney Park IL
You mean the driven gear dropped down? Which is fairly easy to remove.
The drive gear is clipped on to the output shaft and requires driveshaft removal, tail-shaft housing removal, bracing the trans mount, etc, etc.
If that steel clip on the drive gear ever broke off, then . . . . . . . .
The drive gear is clipped on to the output shaft and requires driveshaft removal, tail-shaft housing removal, bracing the trans mount, etc, etc.
If that steel clip on the drive gear ever broke off, then . . . . . . . .
Go Wildcats! 81
C
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
I have seen several speedometer cables with a spring-loaded tip that goes into the tranny. It fits into what they call the bullet.
I recall that spring is a sacrificial part. Supposedly, if there is an issue with any cables or the speedometer cluster gears, that spring will sacrifice itself.
Much easier & cheaper repair than the latter.
I recall that spring is a sacrificial part. Supposedly, if there is an issue with any cables or the speedometer cluster gears, that spring will sacrifice itself.
Much easier & cheaper repair than the latter.