Me & My '59 Apache - The Story Begins

[B52bobardier1]

Hello,

I did not check the operation of the internal spinning cable for the speedometer because both ends were screwed down tightly - no looseness. I have only had this truck since last September and the cable appears almost new - installed by a previous owner.

That's an interesting question about the odometer miles wheels moving or not. I will have to check that.

I have a new "bullet gear" inside this transmission that did correct the speedometer error a little but only by 2-3 MPH. That drive gear that is deeper inside the tailshaft will require the removal of drive shaft and the tail shaft cover and I guess that is what I'm up against at this point. I have no idea which plastic gear is actually installed and I need to find these before I start this job. Its a TH350 transmission with a 3.08 set of differential gears and about 26 inches for a tire height.

Great advice above and I thank you.

Rick

[dsraven]

I have worked on a lot of city delivery trucks, back in the day, and a lot of them had speedo issues due to mileage mostly. some would have the normal square end on the inner cable but if that cable were pulled out a tiny bit the wear area could be seen where it actually was cobtacting and being driven, or was the driver, and often times that area was rounded off. the result was that the inner cable would sometimes move slightly inside the outer cable, and the square part would contact the drive mechanism, so the speedo would suddenly bounce or start to work. another common problem was that the cable would get a tight spot in it due to being pinched or bent to sharply. the result would be that the inner cable would "wind up" inside the outer, until it could overcome the torque required to turn inside the tight spot. this meant the speedo would bounce. sometimes the speedo mechanism would fail but the cable and trans gears were fine. it was apparent because the odometer was still working. some units had a gearbox adapetr attached at the trans to correct the ratio so the speedo would read correctly. these didn't fail often but it seems the steel used for the drive spindle was poor on some and would round off the square reciever part. possibly due to poor metal or maybe a worn out or poor set of internal gears with too much friction or too much friction in the whole cable set up downstream of the trans. sometimes, not that often, it would be due to worn out plastic gears inside the trans due to normal wear or from a hard to turn system downstream of the trans gears.
anyway, my point is, check all the parts before you send your speedo out so that when you assemble it for the last time it won't fail due to another part being "marginal"
the gears inside the trans can be checked visually for obvious problems by removing the cable adapter and looking inside the housing through that hole. turn the driveshaft so you can get a view of the whole gear as it turns. note the color of the gear because different gear ratios use different color gears inside there usually. the adapter is held in place by a U shaped retainer which can be removed so the adapter cab be pulled out. a trans shop or speedo shop should be able to tell you what gear set is required for your rear axle ratio and tire size thats on the truck. sometimes a ratio adapter may be required as well, which also come in different ratios

[dsraven]

speedo drive ratio adatper
https://mrspeedometer.com/products/r...ceat3BG5EC-SAI

speedo drive adapter for turbo 350, removed from trans
https://classictransmissionsolutions...GRyU-w9O20UxCe

https://classictransmissionsolutions...RRt86x7mPVfJGa

speedo drive gear calculator
https://www.tciauto.com/speedometer-...=AfmBOorfY4fqd

[Blackie]

Originally Posted by B52bobardier1

Hello,



I have a new "bullet gear" inside this transmission that did correct the speedometer error a little but only by 2-3 MPH. That drive gear that is deeper inside the tailshaft will require the removal of drive shaft and the tail shaft cover and I guess that is what I'm up against at this point. I have no idea which plastic gear is actually installed and I need to find these before I start this job. Its a TH350 transmission with a 3.08 set of differential gears and about 26 inches for a tire height.

Great advice above and I thank you.

Rick

I use this guide here for speedo gear calculations - but you will need the info above plus your drive gear ratio - they are colour coded so you should be able to yank the cable out and look inside the hole to figure out how many teeth on the drive gear ? https://www.tciauto.com/speedometer-gear-calculator