I've got a 1983 F250 with the BW 1345 transfer case, and I just replaced the speedo gear in the transfer case because it was worn, as well as the driven gear because the speedometer was doing the herky jerky while going down the road. The speedo cable is also new. I got everything back together, and made it two miles before the speedo started jerking around again then just dropped to zero. When I pulled the cable from the T-case, the driven gear was toast. It was all mangled and worn down to sort of a cone shape. Does anyone have a clue what could have caused this? I'm about ready to just give up on having a working speedometer. Thanks for the help.

 

Are you positive they gave you the correct speedo driven gear? If it where me, and everything checks out as far as part numbers and such, I would go to the junkyard and see if it was possible to inspect a unit that is all together and has been working. I would eyeball everything and see how it compares to what you have. Something is not right at the gear area, you just have to figure out what it is.

 

I just replaced what was already there. Everything worked fine for the two miles I drove, and worked correctly. Our county roads are one mile apart, and the speedo counted it correctly.

 

I worked on a vehicle one time where the bushing in the speedo head was dry. It caused it to jerk, and possibly it could also cause drag and wear the gear? Just a guess.

 

Are you referring to the speedo head in the dash? I'm starting to wonder how easily the cable should turn. I can turn the driven gear with my fingers, but it does offer a bit of resistance. I wonder if that little bit of resistance would cause the driven gear to lose its mesh with the speedo gear on the output shaft. I have two turns in the cable. One at the frame alongside the T-case and the other in the engine compartment where it runs through the firewall.

 

Yes, at the speedo head. I seem to remember it turned ok unless I pushed in on the speedo head, which is what the cable seems to do when you plug it in.

 

I read somewhere that most speedo gears have the pitch of the teeth the same, but a few slant the opposite direction. Dont know if its possible to get the wrong gear installed but that would explain what ate the gear up so fast.

 

I guess my next step will be to se if I can get the cable to turn more freely and check out how easily it turns with it plugged into the head versus not.

 

I just spoke to the parts guy at my Ford dealer, and he said that I probably have the driven gear that's sloped the wrong way. It sounds like you may have nailed it Bashby. He said that the speedo will work for a short time before it gets ground into oblivion. Unfortunately, he said he doesn't have a 18-tooth gear with a left-hand slant. I currently have a right-hand slant. He can get a 19-tooth, left-hand which he said would throw my speedo off by about 3mph at 65mph. I don't much care about that as long as the speedo is working and close. Does anyone know who else sells these gears?

 

I found mine on ebay