Howdy gents,

my Speedo is not reading any speed at all. I tested the cable with a drill and it works like it’s supposed to. However, when I screw it back in to the gear adapter, it doesn’t do anything. Could this just mean that I need to replace the gear or should I look elsewhere? Thanks in advance.

VROOM VROOM AMF

 

Rather than resurrecting a thread that's well over a decade old, here's your very own thread. Since you've verified that everything from the cable to the speedo head is working, the problem is obviously in the trans. About the only possible failure is that either the drive or driven gear has stripped it's teeth, or the square drive in the end of the driven gear has worn out and no longer grips the cable. In any case, you'll need to pull the speedo drive adapter out of the trans and inspect the gears. You didn't tell us which trans you have, but the driven gears are all plastic. The drive gear on the transmission output shaft can be either metal or plastic. Inspect the teeth on both. Also inspect the square drive feature in the end of the driven gear. Note that the primary cause of these gears wearing out is that the cable has worn, increasing friction, so consider a new cable and sheath as well, or at least lube the cable inside the sheath, to avoid recurrence.

 

Awesome. Thanks for the help. I’m not really sure what trans I have but the square hole is worn out so I need to get a new speedo gear.

 

How about we start with manual or automatic?

 

It is an automatic.

 

So here's how to figure out which.

 

Thanks for the help. It’s a TH 350

 

Hello everyone. So I’m still having the same issue. I have the 455 with a TH 350 automatic trans. I have replaced the Speedo gear and seal inside the bullet. I have also lubed the cable and checked all connections. It still isn’t functioning at all. Any recommendations on what to do next?

 

Showkahn, what about the drive gear which is external to the bullet, as Joe first suggested...

 

I have replaced the drive gear for the bullet with the 22 teeth that was in there. Still nothing. The square ends of the cable seem fine. Is there a way to replace/ inspect the driven gear in the the trams without taking off the trans?

 

I think you have your terms backwards. The speedo "drive" gear is the one that is around the trans output shaft and requires removal of the tailshaft housing to replace. The speedo "driven" gear is the one that fits in the removable bullet and is "driven" by the "drive" gear. You should be able to see the teeth on the drive gear after the bullet is removed, just look where the gears on the driven gear would be when the bullet is installed. The teeth on the drive gear are spiral shapped, and you will likely need to rotate the output shaft to see all of it. But then, even if a portion of the drive gear is stripped, it would still spin the driven gear on the good-teeth section, so its doubful that only a portion of the drive gear is stripped.

It wouldn't hurt to confirm that the speedo still reads when the trans end of the cable is spun by a drill (following lubrication and any R&R).

 

Yep I had the terms backwards. I have replaced the driven gear and the drive gear seems okay from what I can see in the bullet hole. I did the drill test and the Speedo did work. I’m not seeing any leaking. I’m thinking maybe I should buy a new Speedo cable and see if that fixes it. Do you guys think I should just pull the tail and inspect the inside first? I’m not savvy on trans work past basic maintenance.

 

Your drill test effectively exhaunerates the cable / speedo, so I see no need to bark up that tree any longer. Can you rotate the output shaft to confirm that the drive gear is turning (hard to imagine that it doesn't considering how well it is splined to the output shaft)? Can you confirm that the gear teeth actually engage by installing the bullet and seeing if the driven gear can rotate by hand (it should not be able to be rotated if the gear teeth are meshing)?