1979 Jimmy Speedo Cable

[Rockstar Tendencies]

I need to hook up the speedo cable on my Jimmy how do I do this? Thanks

 

[Molson02536]

I need to hook up the speedo cable on my Jimmy how do I do this? Thanks

Here is a short breakdown of the speedo cable system:

The speedo cable goes into the back of the speedometer head (in dash), then goes down to the tranny tailshaft. There is a plastic speedo gear which slides onto a square end of the speedo cable down at the tranny tailshaft, and it rides on another plastic gear INSIDE the tailshaft. The tailshaft speedo gear is held on to the shaft by 2-3 small metal clip type retainers. If you have OE cruise control, then there is an actuator or transducer mounted on your left inside fender. The speedo cable from inside your dash (back of speedometer head) runs to this actuator, then a 2nd speedo cable runs out of it down to the tranny tailshaft. These cruise control actuators/transducers were used up until 1982 & can also "go bad".

The cable would attach directly to the speedo gear fitting. You won't have a ratio adapter box. It goes in between the speedo gear output on the trans and the speedo cable. Some 77-79 trucks had a ratio adapter box from the factory, like the dually version with the dana 60 rear end. unless the rear axle was changed to a non-standard ratio.

First, disconnect the cable from the speedo and drop it down till you can see or at least feel the end of the cable. After you pull the cable off the trasmission, connect a drill. You can test the cable and speedo by spinning the cable with a drill slowly and see if the inner cable turns. If the cable turns, you know your problem is in the speedo head.

If it doesn't turn, get the rear wheels off the ground and disconnect the cable at the transmission end. Now turn the driveshaft by hand and watch the end of the gear that the cable fits into to see if it turns. If the gear turns, you could have a problem with the cable, or else the square hole where the cable fits in the end of the gear might be bad. If it doesn't turn, remove the gear fitting and look for damage on both the drive and driven gears. You can see the drive gear if you shine a flashlight into the hole you took the gear fitting out of. Broken gears are common and I would check the gears.

Good luck and hope this helps. http://www.compnine.com/largeimg/000000T4-11.gif

 

[Rockstar Tendencies]

Thanks I'll try this