1941 pickup 4-speed speedometer gears

[504d]

I decided it was time to get the speedometer working, which hasn't worked since I bought it.
The inner cable was broken where it attaches to the trans.
That's on order.
Today I tried to figure out if the gears were ok, but I'm not sure.
My thought was that I shouldn't be able to turn an inserted cable if the gears were ok, but I could.
So I removed the speedometer gear case, and when I turned the cable, its gear turned.
The gear looks a little worn, and the worm gear on the shaft a little worse.
But I'm just comparing to pictures.
Does it seem logical that one or both of those gears should be replaced, or is my test bad?
Then, what gears are correct?
The drive gear has 21 teeth and the case says 21.
Is there a more than one 21-tooth gear?
And which worm gear is correct?
When I search for the worm gear for 1941 pickup,
they assume open drive shaft, but mine is closed.
I'm having trouble narrowing the choices to something specific.

Thanks, Steve

[Seth Swoboda]

I've never seen the drive gear in the torque tube go bad. You could install a new turtle gear. That is a pretty easy thing to replace.

[hueyhoolihan]

this post assumes the "gear" being referred to is the "turtle" gear, if not, please disregard.

IIRC, when removing "the turtle" a few months ago while replacing my speedometer cable, i noticed it had the number "18" cast into its housing. it referred to the number of teeth in its gear. it's my understanding that some may have had fewer or a greater number of teeth. new and used ones are available. thinking i needed a new one, i bought a new "remanufactured" one online that turned out (actually it DIDN'T TURN which was the problem) to be defective...win some, lose some, eh?

removing "the turtle" (i've got a '41 ford super deluxe, BTW) is not difficult, but one of the bolts IS difficult to get to. ...just takes time.

if you need a new one, and if you can get yours off, count the teeth and buy accordingly. calculating what it should be involves a lot of variables, many of which are indeterminable, IMO, on such an old vehicle.

[504d]

"indeterminable" seems to be my issue.

I haven't yet found a 21-tooth gear,
only turtles with one already installed.
And those are either very expensive,
or look worse than mine, or both.

Also, the worm gear, the one on the drive shaft,
slides back and forth. Is it supposed to?

Steve

[Seth Swoboda]

Originally Posted by 504d

"indeterminable" seems to be my issue.

I haven't yet found a 21-tooth gear,
only turtles with one already installed.
And those are either very expensive,
or look worse than mine, or both.

Also, the worm gear, the one on the drive shaft,
slides back and forth. Is it supposed to?

Steve

It will have some end play.

[hueyhoolihan]

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Originally Posted by 504d

"indeterminable" seems to be my issue.

I haven't yet found a 21-tooth gear,
only turtles with one already installed.
And those are either very expensive,
or look worse than mine, or both.

Also, the worm gear, the one on the drive shaft,
slides back and forth. Is it supposed to?

Steve

i'm afraid i need some further clarification. it's not clear if we are referring to the speedometer gauge on the dash, or the "turtle gear" mounted to the transmission, when the phrase "worm gear" is being used.

have both been taken apart or removed from the car? if so, which ones are they, and which gears of each are we referring to when speaking about worn gears, or turning or not turning when a test is performed?

[504d]

About 1/2" end play ok?

PXL_20260311_220508706.jpg

PXL_20260311_220451869.jpg

[hueyhoolihan]

Originally Posted by 504d

About 1/2" end play ok?

Attachment 582683

Attachment 582684

it's probably fine. remember when in reverse, the "turtle gear" may have to disengage to protect the speedometer gauge. meaning that the worm gear inside the torque tube may purposely slide fore and aft to perform properly. IDK for sure though. ...just surmising. it could even be spring loaded. and the spring may (hopefully not) be broken. anyway that's another possibility..they are endless, i'm afraid.

i think i'd just put it back together the way it is, along with the new cable and see how it goes!

[petehoovie]

Originally Posted by 504d

About 1/2" end play ok?

[Bob C]

Looks like the snap ring is missing. Maybe it got pushed up by the u-joint.

[504d]

Thanks. I'll hunt for that tomorrow.

[petehoovie]

Originally Posted by Bob C

Looks like the snap ring is missing. Maybe it got pushed up by the u-joint.

[504d]

Originally Posted by Bob C

Looks like the snap ring is missing. Maybe it got pushed up by the u-joint.

Unfortunately, no sign of the snap ring.
I think, for now, this gets put back together
and back on the todo list.

Thanks all,
Steve

[petehoovie]

Originally Posted by 504d

Unfortunately, no sign of the snap ring.
I think, for now, this gets put back together
and back on the todo list.

Thanks all,
Steve

[504d]

Fyi, the speedometer itself does work right either. I hooked up the new cable to the speedometer. Turning the cable end slowly by hand caused the needle to slowly go up and stop when I stopped. Turning it backwards slowly caused it to go down slowly. So, that gets added to the todo list too

Right now I'm just trying to get the truck ready to pass Delaware inspection.
I'm guessing this doesn't really need to work for that.
I think only the wipers are left

Steve

[Kube]

[QUOTE=504d;2441898]About 1/2" end play ok?



No, absolutely not. There should be a circular ring in there to hold the drive gear in position. Yes, there is a little end play, a little, perhaps .030".
I'll look through my driven gears and see if I have a 21 tooth assembly.

[Mart]

The gear might drive ok if slid back to it's natural position. I looked at the cut of the helix and I think it would drive the speedo al right in forward motion. If reversing, though, the gear would pull itself forward and might move far enough forward to lose drive.
You would need to pull the rear end back to allow the missing circlip to be fitted. If you were sneaky you might be able to loop some wire around there and twist the ends so you have a makeshift retainer to avoid pulling the rear back. The correct clip could be fitted at the next convenient time.

[Als48]

Hey Mart/504d, looking at the enlarged photo in post #13 and 14, could that be the snap-ring seen on the spline to the left of the groove? If so maybe it could be coaxed back into the retainer groove on the splined shaft and keep the speedo worm gear in position.

Al H

[504d]

Originally Posted by Als48

Hey Mart/504d, looking at the enlarged photo in post #13 and 14, could that be the snap-ring seen on the spline to the left of the groove?
Al H

I thought that might be the case too, but it's really the end of the universal joint.

I'll try Mart's wire idea, and things like it. I thought maybe I could trim an actual snap ring enough that when maximally expanded. It could slip over the shaft into the groove.

Thanks,
Steve

[504d]

I meant to attach the universal showing the rear boss at right.