The speedometer cable in our 1972 145 4spd+OD passes through a firewall hole on the passenger side. The speed indicated was jumping around, so we replaced the old cable with a new one.

First, we were able to tie the old cable's end to a string under the dash and pull the cable free from the engine compartment side of the firewall, trailing the string along. Then we tied the new cable's end to the string and pulled it through the firewall to the right place under the dash. That was great, except that I lost hold of the cable end trying to mate it to the back of the instrument cluster, and it slithered back too far. So, tip #1, when the cable is close to being attached, tie it to something temporarily so it won't slither out of reach. (On my second try, I tied it by the firewall hole, in the engine compartment.)

Then, we had to figure out the proper routing under the dash. Tip #2, when sending the cable in through the firewall from the engine compartment, it has to pass around the far side of the heater enclosure. That's clockwise looking down from the roof. So, from the engine compartment, aim the cable's end through the firewall hole toward the top of the vertical face of the dashboard in the very center of the car, not along the firewall behind the heater. (This info is not in any of the manuals we have.)

Tip #3, remove the dash's ashtray and look and/or light through the hole. A flashlight and "long fingers" flexible grabber were useful to me. (Amazon calls it a "Flexible Claw Pick Up Tool Automotive Mechanic Shop". Don't search for "long fingers", heh.)

During my struggle, I looked online for advice and didn't find any. I promised myself to post when we succeeded. I presume this will also work for 142 and 144 models.

Keep 'em shiny side up. KGHN