[69coupe]

I'm looking for some guidance on a speedometer problem I'm having related to a transmission swap.

I have a '69 Mustang that I have swapped out an FMX and installed a "correct" toploader. Due to the swap I needed to change the speedo cable as well as the driven gear to match up with the toploader.

The problem is that the cable is now turning the wrong direction for my speedo ... it's turning counter clockwise (looking from the driver's seat) instead of clockwise. The speedo does not register unless I am going in reverse!

I have double checked that I have the correct cable and driven gear, so now I'm stumped.

Any suggestions would be a great help.

Thanks

 

[jay67fast]

I suggest you re-check your speedometer driven gear. All the info I can find shows that the driven gear for an auto trans is a right hand gear, and for the 4 speed it is a left hand gear. Logic says that the opposite hand gears turn in opposite directions, so if your speedo is only operating in reverse, then you have the wrong type driven gear in there now.
Hope that helps,
Jay67fast

 

[69coupe]

Thanks for the information.

My research showed the same thing so I checked my receipt for the part and it is listed as a LH gear. It may be possible that I got something different than what I paid for ...

Does anyone know if it is possible to actually install a RH driven gear and have it mesh up properly with the drive gear? If not then I must have the correct gear in there since it is turning the cable. If it is possible to put either the LH or RH gear in and have it mesh, then maybe I do have the wrong gear. I hate to pull the cable out for no reason if only a LH gear will actually fit in.

If I do have the correct gear and it is turning the wrong way ... then what?

This is frustrating!

 

[jay67fast]

I recently changed rear end gears and had to change the driven gear. In fact, I did so yesterday! I had the old gear out and the new gear in in less than 20 minutes. It took longer to jack and support the car than it did to change the gear! It's only one bolt to come out, you can check the gear without removing the gear from the cable and re-install it in less time than it took me to reply to your post. Then you can order what you need and replace the present gear when you reeive ithe new gear from the vendor.
The point is: if the gear in your tranny now is a left hand gear, then you need a right hand gear. If the gear in your tranny is a right hand gear, then you need a left hand gear. What you're trying to do is to reverse the rotation you have now.
Keepme posted on the results.
Jay67fast

 

[69coupe]

Found the Problem ...

Thanks for the advice jay67fast ...

I removed the speedo cable only to find that my new driven gear had been demolished! It was the correct LH gear, so this was puzzling.

I removed the tailshaft and found that the drive gear was incorrect ... it was the one used for a three speed transmission that has the speedo cable entering from the driver's side of the tailshaft instead of the passenger side. It would mesh ok with my old RH gear, but would rotate the wrong way. When I originally put in the LH gear it chewed it up because it did not mesh properly.

The solution is to get the proper drive gear and another LH drive gear.

I bought the transmission used and had it rebuilt ... somewhere along the line someone put in the wrong driven gear. A giant pain in the rear, but at least now I know what was wrong.

Thanks again for you responses.