Help from you Tinker Types
 

My truck likes to mess with me. As soon as I get it “done” it will find something else to mess with me.
I have an original Stewart Warner Step Up/Down Speedo cable speed corrector. It makes the Speedo dead on to my GPS speed test and appears to be from the 70's aftermarket.
The other day, out of the blue, the speedo started a death jump. Minutes later no speedo. Did the cable test with a drill. All good. Went on to the speed correction device and proved to be free wheeling.
A simple device it looks like a model of a 1 speed transmission. Two shafts with tiny pressed on gears and a intermediate stepper gear. The gear on the slave shaft that is presses on has come loose and will not hold to the shaft.
As far as I know, no longer produced and no parts I need to somehow affix this gear to the slave shaft. What do you recommend?
Solder
JB Weld
Foil and tap back on
Other Ideas Appreciated.

Re: Help from you Tinker Types
 

Is there a groove on the shaft by any chance, such as one formerly occupied by a snap ring?
Any metal floating around down in the gearbox that might provide some forensic evidence of what may have let go?

Re: Help from you Tinker Types
 

Knurl the shaft and press back on with green locktight (or you can prick-punch the shaft in a pattern to raise the material and green locktite on).

You need to raise enough material to make it a press fit.

Works for low load applications.

If you have a drill press you could drill the gear and shaft for a spring pin.

Check the gear well, it may have a crack that caused it to lose it's press.

Off topic, but for some reason it really sets me on edge if someone asks if I've been tinkering on my truck. I never tinker.

Rg

Re: Help from you Tinker Types
 

No snap ring or keeper. These are pretty small parts. The shaft at the point the gear is pressed onto is 0.250 using a Harbor Freight digital caliper. In the photo it is the medium sized section on the shaft with a bit more shine than the rest. I think I know what I did wrong upon reattachment of the cable last month. Over tightening caused the tip of the cable to push in the shaft and making the meshing of the slave or output shaft gear bind against the intermediate gear. No shrapnel. I just need to get this tiny gear not to slip on the output shaft. Another thought is Loctite. Red or maybe green penetrating type. The relation between the gear and shaft is tight but not so tight as to hold. I don't like the foil idea. I feel that will be way too thick and split the gear.

Re: Help from you Tinker Types
 

You just posted as I was typing. The little shaft is pretty small. But I think I was coming to this same conclusion. These are pretty small parts so damage and or over doing is a risk.

Re: Help from you Tinker Types
 

PB, you're experiencing that old adage, "The more parts involved, the more chances of something failing".. The simple "tinkering" solution is eliminating those extra parts.

When I first brought home my recent C-10, its speedometer was way out of calibration.. According to my GPS, at 60 mph, the speedometer indicated a speed of 85 mph.. I used TPI's calculator to determine the correct drive gear and driven gear for the speedometer.. Using their calculations, I installed the gears and now that speedometer is dead on with my GPS unit..

Here's the link to that site:

https://www.tciauto.com/speedometer-gear-calculator

Re: Help from you Tinker Types
 

Rusty
I tend to agree, and if I for sure knew the diff ratio, somewhere near 3.50, I could calculate. These little devices were very common. Dropping the Diff cover to count gears, since I can't recall what it was 2 yrs ago when I changed fluid, is an option.
One question relative to changing the slave gear in the tail housing. Do all these color gears mesh to the same gear on the tranny output shaft? Or does the gear on the output shaft require a swap as well. If so, with the tailhousing removed, can a simple puller pull the gear off the output shaft? Am I over complicating it?

Re: Help from you Tinker Types
 

User jimmy70 had some for sale a while back. I don’t know if he has any left. Google “speedometer ratio adapter” to find used ones. Other companies still seem to sell them. Such as https://www.texasindustrialelectric....er_Adapter.asp

Re: Help from you Tinker Types
 

PB There are a range of drive and driven gears.. Each drive gear can accompany an assortment of driven gears.. Thus providing for a wide range of tire sizes and differential ratios.. IIRC, in some of your past posts, you have a TH350 transmission.. Simply remove the tail housing.. Be sure to have a pan handy to catch the small amount of fluid.. No puller is required to remove the gear.. A "hand operated" clip is used to retain the gear.. The output shaft has a hole in it for a tab on the clip. The gear has a slot in the I.D. similar to a wide keyway to capture the clip.. Pinch the clip with your fingers and the gear will easily slide over the clip.. The clip doesn't come away with the gear, rather it remains on the shaft.

You must know the differential ratio or the computations will be inaccurate.. Remove the cover.. No need to "count teeth", as the tooth count is stamped on the edge of the ring gear.

Re: Help from you Tinker Types
 

Cutting a keyway with the world's smallest shaper is always an option ;-)

Might be able to get a grub screw in radially, but I like the idea of staking it to the shaft. Guessing the shaft is malleable, but the gear might be brittle

Like the others, I'm wondering how that press fit came apart all of a sudden

Re: Help from you Tinker Types
 

I agree with Rusty on trying to eliminate the speedo converter if possible.

If you don't want to pop the rear diff cover, you could jack up the rear end, mark the wheel and drive shaft and count how many drive shaft revolutions it takes for the wheel to make one revolution to get a ballpark ratio.

Or, when I had to change my 700R4 speedo gear after having my diff rebuilt into a 3.42, I drove it with the GPS speedo app to see how far it was off and got a gear to correct it (39 tooth brown driven gear in my case). I think the rule of thumb is 1 tooth for every 5MPH or 10%, but can't recall for sure. If your speedometer is showing a slower speed than you're actually traveling, then you'll need a driven gear with less teeth to "speed" it up.

Re: Help from you Tinker Types
 

Aha! I thought I saved the calculations when I swapped gears. My speedo was reading higher than actual since I went from 3.07 to 3.42. Speedo showed 80MPH while actual was 70MPH, a 14.29% difference. I added 3 teeth to the driven gear to slow down my speedo (roughly 5% per tooth, not every 5MPH). If you're lucky, your existing drive gear on the tail shaft won't need to be changed and you can just change the driven (pencil) gear that fits into the bullet, shown with the red arrow.

Re: Help from you Tinker Types
 

Do any of these look like yours?

https://67-72chevytrucks.com/vboard/...meter+gear+box