New Speedometer Question

[elimin8tor65]

Im in need of a new speedometer. The one Im looking at buying says its the one Im gonna need. The only issue im not sure about is where it says "Speedometer 0-85 MPH W/O Speed Sensor Chevrolet C10 1981-1987". What is a speed sensor with regard to my speedometer needed for? All im doing is replacing the gauge. My old one worked fine, I just broke the needle and also want a newer looking gauge. Do I really need a new speed sensor? Thanks​

 

[YakkoWarner]

I know on the squares that use TBI, there is a speed sensor that relayed the vehicle speed to the computer. If your truck has a carb instead of a TBI, its a pretty good bet you won't need to worry about the speed sensor.

 

[Zelph]

Should be a little green box mounted behind the cluster.

 

[Gander]

I know on the squares that use TBI, there is a speed sensor that relayed the vehicle speed to the computer. If your truck has a carb instead of a TBI, its a pretty good bet you won't need to worry about the speed sensor.

VSS was on the back of the speedo for at least a couple of years before the 1987 TBI squarebodies. I think back then it was pretty much just a speed sensor for cruise control but not sure. Pretty sure it was on there back of the speedo for at least a couple of years prior to the 1987 TBI trucks

 

[ali_c20]

VSS is connected to the ECM and gives input needed for fuel, EGR, torque converter lockup and other things afaik.
Speedos with VSS and VSS buffers are available online.

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[WesN]

1981-1983 use a mechanical/electric resumeable cruise control with speedo cable in and out. 1984 and up use an electronic cruise control which would require a VSS tied in with no speedo cables attached to the cruise control.