Quote:
Originally Posted by smogdave
I just have to figure out how to use a speedo cable in ther TH 400 with the speed sensor. If you have any ideas let me know.
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There is only one option for your '76 that I am aware of: get an
"2PRS" adapter from JTR. You can mount this anywhere along the speedo cable as it has the same male and female connections as the speedo cable. Wiring is dead simple as the 2PRS has only two wires: one side is grounded and the other wire connects to the VSS signal wire to the ECM.
I originally installed a 2PRS at the end of the speedo cable that hooks into my cruise control transducer because it was easy to get to and install, but my speedo cable is pretty long (or worn) and the speedo cable wind-up resulted in wildly fluctuating signals to the ECM at low speeds. By wind-up, I mean when the friction in the speedo cable builds/twists up and releases the tension at low speeds - if your speedometer needle swings back and forth (especially at low speeds), you have wind-up. To get a good low-speed signal, I ended up mounting the 2PRS at the speedo cable output on the transmission itself.
If you had a later model truck (which I do, but didn't go this route), you could also get an '87-'89 instrument cluster with the VSS optical sensor built in. This option also requires the green box thing and light pickup mentioned a few posts back.
Good luck,
Mark