The Stovebolt Site Forums The Shop Area Driveline Speedo bullet

Has anyone adapted a speedometer cable bullet to an SM 420 tranny?

Thanks!

Sorry about my ignorance, Saluki, but what is the "cable bullet"

Maybe you are referring to one of the "speedometer gears"?

"Speedometer gears include both a drive gear and a driven gear. The drive gear is located on the transmission's output shaft. The driven gear is positioned in a removable housing that is typically located in the transmission's tailhousing." (from TCXI automotive)?

I think I now know what the "bullet" is, Saluki (I did a Google search).

I only know Stovebolt gears - I think the "bullet" is an integral part on one of the original gears?

I think that you need a gear set (drive & driven) that matches your drive-train gear ratio (and your transmission attachment hole). Someone will correct/clarify this, I hope.

The bullet is the adapter part that goes into the transmission housing that you hook the speedometer cable into.
Sorry I was not clear. It is a newer version that holds the driven gear. I also saw on eBay (I think) an SM 420 driven gear housing that appeared to have a plastic gear instead of the old metal gear.

IF that is possible I could replace the drive gear and driven gear. I currently have a 4 tooth drive gear and a 13 tooth driven gear that is a bit too slow. So I either change the gears or get an adapter to speed it up.

Earlier discussion on this: https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=921081

I'm interested in this subject. I have a piece of paper with the speedometer reading to the actual speed written on it; not convenient but it works.

I have been using a GPS and I do understand the easiest thing to do is get a ratio adapter. I was just curious if anyone knew of a modification that I might also use.
With the number of 420 trannys out there I thought there might be another option.

Thanks for the link Gord&Fran, I also have a 54 1/2 ton.

If I knew what plastic gear would fit that old adapter, I would also change the drive gear. I could put in an 8 tooth drive gear and a 22 tooth driven gear.

There seems to be lots of gears for automatic transmissions and the 4 speeds found in muscle cars. But we have the SM420...

I'm still not settled on the ring and pinion gears in our truck. We might make a change there so I'm not too anxious to get the speedometer reading corrected now. Plus, our speed limits are in Km/h so I'm kind of used to doing conversions in my head.

I don't know if they are all the same but my speedometer is adjustable. Kind of trial and error but I was able to dial mine in pretty well.