Mech Smith's Speedo bouncing a little?

[davids2toys]

When I bought my car the speedo stopped working or was not working correctly immediately. The cable is actually to short or has too much back and forth movement inside the sheath. Turned out to be two items.
It would be able to travel into the reversing adapter at the speedo to far, by this happening it backed out of the plastic gear in the tranny eventually killing the square drive opening. With Doug's(ERA) guidance, made a 3/8 long shim out 1/8 brakeline and installed it right on the cable at the adapter end. This prevented it from walking out of the tranny gear to far and ruining it.
Your problem of the intermittent jumping around sounds like it could be the end of the tranny gear. If I am right, it will get worse as the square drive gets more destroyed until just won't work at all.
The good thing is this gear was designed to be the sacrificial lamb, that is why it is plastic and cheap

[DanEC]

Originally Posted by davids2toys

When I bought my car the speedo stopped working or was not working correctly immediately. The cable is actually to short or has too much back and forth movement inside the sheath. Turned out to be two items.
It would be able to travel into the reversing adapter at the speedo to far, by this happening it backed out of the plastic gear in the tranny eventually killing the square drive opening. With Doug's(ERA) guidance, made a 3/8 long shim out 1/8 brakeline and installed it right on the cable at the adapter end. This prevented it from walking out of the tranny gear to far and ruining it.
Your problem of the intermittent jumping around sounds like it could be the end of the tranny gear. If I am right, it will get worse as the square drive gets more destroyed until just won't work at all.
The good thing is this gear was designed to be the sacrificial lamb, that is why it is plastic and cheap

I can see this - first time I re-installed the cable to the speedometer and took a test drive the speedo didn't work at all. Pulled it back off and realized it wasn't inserted into the transmission gear. Made sure it was engaged in the transmission gear and reinstalled it and it was working again. It surprised me that I could install it and snug up the fitting and it the cable wasn't engaged. What you related is apparently what allowed it. I will see if I can rig up a couple small washers to go between the shoulder on the cable and the reverser to back it up a little and ensure full engagement in the transmission. I also took the reverser apart but it seemed smooth in operation and well lubed so I decided to put it back together and give it another shot of chassis lube in the zerk fitting.

I took another short drive but it started misting and had to curtail it. Still bouncing a little although seems slightly better. It seemed to get worse the other day after I accelerated up through the gears to about 70. I suspect it may be in the transmission gear - hopefully the driven gear. But it looks like I will have to pull the tunnel to get a good look at it.

[davids2toys]

Originally Posted by DanEC

I can see this - first time I re-installed the cable to the speedometer and took a test drive the speedo didn't work at all. Pulled it back off and realized it wasn't inserted into the transmission gear. Made sure it was engaged in the transmission gear and reinstalled it and it was working again. It surprised me that I could install it and snug up the fitting and it the cable wasn't engaged. What you related is apparently what allowed it. I will see if I can rig up a couple small washers to go between the shoulder on the cable and the reverser to back it up a little and ensure full engagement in the transmission. I also took the reverser apart but it seemed smooth in operation and well lubed so I decided to put it back together and give it another shot of chassis lube in the zerk fitting.

I took another short drive but it started misting and had to curtail it. Still bouncing a little although seems slightly better. It seemed to get worse the other day after I accelerated up through the gears to about 70. I suspect it may be in the transmission gear - hopefully the driven gear. But it looks like I will have to pull the tunnel to get a good look at it.

I am only referring to the Toploader 4 sp, washer are not going to do anything for you, a spacer has to be put on the cable itself to limit its walking inside the sheath into the reverser to far. By the sounds of it, sounds like your plastic gear is shot. as I said, very cheap(18.00) and no need to pull the tunnel to R&R. I have 331 gears and it would be the green gear. I think the tooth count was 18 or 21...don't remember.
Edit:sep1 10:52
Never saw the part where you made the spacer...sorry

[DanEC]

Originally Posted by davids2toys

Your problem of the intermittent jumping around sounds like it could be the end of the tranny gear. If I am right, it will get worse as the square drive gets more destroyed until just won't work at all. The good thing is this gear was designed to be the sacrificial lamb, that is why it is plastic and cheap

My initial success reveresed upon pulling the reverser apart and cleaning it out and lubing it with break in lube. Everything topside is lubed, graphited and shimmed to close tolerances, so I suspect I'm losing my plastic gear in the transmission. Anyone remember which speedometer gear goes with a 3.31 rear - 18 tooth??