Our 1965 Clark Cortez motorhome’s speedometer needle was bouncing so much that a spring could have been attached to it.
What was troubling was that L and I were actually going about ten miles per hour … but our gauge could not decide if we were going speeds of zero, ten, or even twenty miles per hour so accuracy was not its strong point.
This discovery was made back in 2019 when we drove our Cortez for the first time to work on its brakes.
However, a working speedometer did not really matter when trundling around on the farm to fix more serious jobs, but one day — one distant day far into the future — we would love to actually go further than a mile in the Cortez and, therefore, we need to be know how fast (or more likely slow) we are going.
Plus, finding and fixing the cause of our bouncy speedo should have been easy … though all supposedly ‘easy’ jobs take far longer and, more often than not, turn into three different jobs.
To see exactly what was causing our speedometer problem, I set about removing our cable by jamming my hand behind the dash. After scrapping the skin off my knuckles during several tries, I learned this is a relatively easy job if you have baby-sized hands, double joints, or/and a high pain threshold. Therefore, L stepped in with her small hands and disconnecting the cable from the gauge. After that, I crawled under the Cortez to disconnect the cable from the transmission. This was a simple case of undoing the locking nut, though the task was unpleasant based on how oily and dirty the transmission was and how many spiderwebs, egg sacks, and mud dauber (English readers, think inch-long, kinda chill but still wasps) nests there were!
With both ends free, it was a case of pulling the cable through the cradle and out of our RV while taking note of the route — which L always supports because often I take things apart then struggle on getting them back together or remembering where they go.
Looking at the condition of the cable, the drive key (the end of the cable) was slightly worn, leading me to believe it was not engaging with the gauge.
Setting out to find a replacement, I researched digitized old documents on a Cortez Facebook page and found what was needed — a part number for a long 10-foot speedometer cable. Shortly after, one was ordered so we returned to the Cortez to install it.
I attached the cable at the transmission end while L threaded the cable through and up to the gauge.
Now we needed to test our work so I fired up the Cortez — which started for the first time, no messing (shocking, I know)! Unfortunately, as we inched forward in oursteel beast,the needle didn’t move on thespeedo gauge. Even pressing my foot on the gas petal lead to nothing. Bugger!
As usual, our ‘easy’ job became the opposite:Disconnecting the cable from the transmission, I attached the drive key to my electric drill to test if the cable was spinning and engaged with the gauge. With a quick whizz, the speedo burst to life as L excitedly screamed from the driver’s seat, confirming that our Cortez was going over 90 miles per hour! Happily, holding the needle steady at five miles per hour, this proved there was a problem at the transmission end, though I was puzzled.
Analyzing the original cable, we noticed the transmission drive key size was larger than the new one, which meant the new cable was still not being driven from the transmission. This also meant going home and researching again …
More ideas later, I purchased an adaptor to go from the drive key to the transmission. However, this did not work either.
Still more research later, we decided to have a custom cable made because the Cortez is a bit of an odd duck — like having a 10-foot long speedo cable with one end that’s a 0.155-inch square drive and the other end, a 0.104-inch square drive.
We are sure there is an ‘off-the-shelf’ cable out there … somewhere … but having one made turned a job that was a blackhole-of-time-and-effort into one that was simpler. Better yet, the company was great — They made it and shipped to us in one week!
Returning to our Cortez yet again, L installed the new cable within minutes and a short test drive later gave us a far steadier speedometer needle when driving.
Being honest, the needle is still not perfect — We checked the speed against Google Maps and were about one mile per hour off at 15 miles per hour — but I’m hopeful that a bit of a gauge clean will help that.
Now far more difficult jobs are ahead so be sure to subscribe to get notifications of when they are published!
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