Trying to figure out why my 85 F250s speedo and odo don't work. It was switched to carb and there's wires everywhere. Should I be looking at the trans or the rear for a speed sensor? I wanna replace that first to see f it solves the problem.

 

You have a speedo cable.
Look at the transmission tailshaft housing. (TC if 4x4)
There are plastic gears inside that may be worn out.

 

Easy replacement if they're worn out? If I have to pull the whole transfer case I'm not gonna bother with it.

 

Easy if the gear on the output shaft is not shot.

There should be a little 'fork' holding the cable in.

Which transfer case do you have?

 

Its easy as heck if you just need to replace the speedo gear, one bolt and a retainer clip. If the gear in the transfer case is worn you will need to disassemble it to replace it.

BTW check your cable as well, I've one kink up inside the rubbery housing which made my speedo jump around.

 

T18 I think? Does that sound right? I was just under there and now I forget.

 

T-18 is a four speed iron toploader gearbox.

You may have the Borg Warner 1345 or a New Process TC.

 

Really
First try removing the cable and spinning it to see if the cable or speedo is broken.

If the plastic driven gear on the end is mangled you need to match it for color and tooth direction.

If the drive gear is mangled, then you have to disassemble.