Strange noise and bouncy speedometer needle

[71threequarterton]

So I got on the road to work this morning and all of a sudden I started hearing a loud noise which sounded like radio static at first. I reached over and turned off the radio but the noise didn't go away. With the radio off, I could hear it a little more clearly. It sounded like higher pitched grinding, rotating sound, much like the pitch of radio static though. As I came to a traffic signal the rotational sound slowed down and stopped as the truck came to a stop. At the time this was happening, the speedometer needle was going nuts: spinning all the way well past its limit and then back down to zero and just bouncing all over the place. As I accelerated, the noise came back and slowed down as the truck slowed down and then stopped when I came to a stop. The whole time, the speedometer meter was bouncing around erratically. Does this sound like some kind of gear drive that has mostly disengaged or has ground down to the point that it barely engages? I've never heard anything like this before. The motor seems to run fine regardless but I drove it home and parked it because I have no idea what this is or what I might be making worse if I drive it. Had to drive the wife's car to work

[bw46]

Speedometer cable might have failed. They're relatively easy to replace and inexpensive. They come in several different lengths. I recommend removing yours, inspecting, and measuring the length if you intend to buy new.

Note that sometimes you can just remove the internal cable and grease it, but it sounds like yours was catastrophic and will need replacement.

[truckster]

I would pull the inner cable out, clean it thoroughly, and lube it with white lithium grease. I'll bet your problem goes away.

[Elliot949]

Definitely a dry Speedo Cable... lube it up and you will be fine... do it before it binds up and breaks...

[LockDoc]

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If the speedo still works OK at lower speeds I'm guessing the cable just needs lubed also.... Unscrew it from the speedometer, pull the cable down where you can see what you are doing, and pull the inner cable out of the housing. Inspect it to make sure there are no frayed areas, spray some good penetrating oil down inside the housing, put a thin coat of grease on the cable and insert it back into the housing, twisting it as you go. Screw it back into the back of the speedometer, making sure that the inner cable is inserted into the speedometer head. Test drive it and see if it functions OK.

LockDoc

[71threequarterton]

I really appreciate all the help, everybody.

[hamjet]

you could just disconnect it at the tranny and take it for a ride to see if its gone..

[slikside]

Sub'd...I need to do this too! I notice mine when it's a bit cooler outside. Never happens in the summer.

[LockDoc]

Originally Posted by slikside

Sub'd...I need to do this too! I notice mine when it's a bit cooler outside. Never happens in the summer.

If it isn't really dry (no lube) then what lube that's in it is hard and gummy. Cold temps make it worse and that is why it shows up during cold spells. If you don't correct it it will end up winding your inner cable into a pretzel or ruining your speedometer head....

LockDoc

[El Dorado Jim]

mine just started doing this also, thanks everyone for the great tips

[71threequarterton]

So I finally got a chance to get under there and have a look. Please excuse all the newbie questions - this is my first time dealing with this.

First off: That whole assembly that I'm pointing to with the blue arrow is loose. I can easily shift it around with my hand.

I also saw a little pin, maybe 16th" in diameter, sticking out of the side of that box. I pushed it in and that's why you don't see it.

There's a little tranny fluid leaking out of there as well. I'm guessing because that bolt circled in red is loose. What happens if I remove that bolt? Does that take the whole assembly off and tranny fluid will start leaking out?

Should I be able to just pull off the end of the speedo cable that I have circled in yellow and just drive it?

Thanks again for the help!

[LockDoc]

Originally Posted by 71threequarterton

So I finally got a chance to get under there and have a look. Please excuse all the newbie questions - this is my first time dealing with this.

First off: That whole assembly that I'm pointing to with the blue arrow is loose. I can easily shift it around with my hand.

I also saw a little pin, maybe 16th" in diameter, sticking out of the side of that box. I pushed it in and that's why you don't see it.

There's a little tranny fluid leaking out of there as well. I'm guessing because that bolt circled in red is loose. What happens if I remove that bolt? Does that take the whole assembly off and tranny fluid will start leaking out?

Should I be able to just pull off the end of the speedo cable that I have circled in yellow and just drive it?

Thanks again for the help!

Yes, the converter will be loose. As long as the knurled nuts are tight it will be fine. I don't know what the pin would be. If the transmission isn't over full or it isn't parked with the front of the truck uphill it shouldn't leak much fluid if you remove the bolt and pull the speedometer gear unit out. Just go slow and watch that you don't catch the plastic speedometer gear on the side of the hole and pull it out of the housing, it will drop down inside of the trans. There should be an "O" ring on the bullet shaped speedometer gear unit. I can't remember if there is an "O" ring on the inside where the plastic gear shaft goes through or if the spiral grooves in the shaft just carry the fluid back to the transmission. You can pull it out and check it.

Yes you can disconnect the speedometer cable and drive it.

LockDoc

[71threequarterton]

Originally Posted by LockDoc

Yes, the converter will be loose. As long as the knurled nuts are tight it will be fine. I don't know what the pin would be.

So, LockDoc, I guess the part that's confusing me is I haven't seen that box shaped part that the blue arrow points to in my picture on any of the examples I've seen.

I've found a bunch of examples of TH350/speedo bullet/cable assemblies and none of them have that part - they all just show what looks like the cable connected directly to the bullet going into the tail housing.

Can you tell me a little more about the converter, like is it to compensate for different gear ratio or tire size? I don't know exactly what to call it so I have not been able to find anything that looks like it in order to learn more about that part...

[LockDoc]

Originally Posted by 71threequarterton

So, LockDoc, I guess the part that's confusing me is I haven't seen that box shaped part that the blue arrow points to in my picture on any of the examples I've seen.

I've found a bunch of examples of TH350/speedo bullet/cable assemblies and none of them have that part - they all just show what looks like the cable connected directly to the bullet going into the tail housing.

Can you tell me a little more about the converter, like is it to compensate for different gear ratio or tire size? I don't know exactly what to call it so I have not been able to find anything that looks like it in order to learn more about that part...

A more technical name for it would be "ratio adapter" or "speedometer compensator". If you put both of those terms in your search string more will come up on it. Yes, it is used to correct driveline ratio problems.

LockDoc

[71threequarterton]

Originally Posted by LockDoc

A more technical name for it would be "ratio adapter" or "speedometer compensator". If you put both of those terms in your search string more will come up on it. Yes, it is used to correct driveline ratio problems.

LockDoc

Boom! Came right up when I searched for that. Thank you, sir!

[71threequarterton]

Crawled under there yesterday and zip tied the speedometer cable to the frame and pulled this Stewart Warner converter off the speedometer bullet.

The yellow arrows point to the "pins" I referred to in my earlier post. One of those was sticking out. I'm gonna take it apart to see what everything looks like in there and probably just reinstall it once I get a new bullet which I think should fix the leak.

I disconnected the cable from the speedometer and attempted to take the cable clear out of the truck so I could measure and inspect it but there were a few other wires going through the same hole in the firewall preventing me from pulling it through and I chickened out

I need to clear some more junk out of my garage before I can pull the truck in there and really dig into it - being a newbie to most of this stuff, I'm afraid if I do something to the truck it might not start right back up again

[LockDoc]

Originally Posted by 71threequarterton

Crawled under there yesterday and zip tied the speedometer cable to the frame and pulled this Stewart Warner converter off the speedometer bullet.

The yellow arrows point to the "pins" I referred to in my earlier post. One of those was sticking out. I'm gonna take it apart to see what everything looks like in there and probably just reinstall it once I get a new bullet which I think should fix the leak.

I disconnected the cable from the speedometer and attempted to take the cable clear out of the truck so I could measure and inspect it but there were a few other wires going through the same hole in the firewall preventing me from pulling it through and I chickened out

I need to clear some more junk out of my garage before I can pull the truck in there and really dig into it - being a newbie to most of this stuff, I'm afraid if I do something to the truck it might not start right back up again

I've never had one apart but I would suspect that the pins are retainers for the male and female threaded couplers. It should be pretty simple inside, probably a couple of small gears and a shaft.

The wires through the speedo firewall hole must be something added by someone. Generally there is a rubber grommet with just the speedo cable.

LockDoc

[71threequarterton]

Originally Posted by LockDoc

The wires through the speedo firewall hole must be something added by someone. Generally there is a rubber grommet with just the speedo cable.

I saw where I could disconnect one of the wires and pull it through the grommet first to make more room to pull the speedo cable through but I'll need to trace the other two wires that are in there. I might need another set of eyes to help me with that though.