How do I find and replace the speedometer cable? It is intermitently working. The speedometer needle tends to "bounce" around a lot.

Right off the bat it sounds like a broken speedometer cable. As the cable spins from the gearing of the transmission it is clicking against the broken part of the cable running to the speedometer gauge. The frictional clicking is what's causing your needle to bounce around. Since the cable is probably broken and cannot spin long enough to move the odometer numbers. Raise your vehicle safely and disconnect the speedometer from the transmission. then see if you can pull the cable out of the housing. If only a portion of the cable comes out, then that should answer your question. Be careful when you disconnect the speedometer cable from the transmission as not to lose any small pieces that cause the drive mechanism to work.

The needle bounce may be related to the cable, it may be broken or just needs lube.
Remove the speedometer cable, locate the connection at the transmission and unscrew it, then locate the connection at the rear of the speedometer, remove the cable from the car, pull cable out of plastic housing and see if it comes out in two parts, if it does then cable needs replacing.
You will see the cable has two ends, is the cable is broke replace it, a broken cable will sometimes spin and not spin causing needle to jump, also a binding cable will do the same, if cable is good then spray wd40 in to cable and spin by hand. note; if cable is binding you will need to work it so it does not break. good day

There is a plastic helical gear in the transmission, where the speedometer cable attaches. Start there. Usually 2-3 bolts that hold it in, when it comes out, some fluid will escape. Check that gear for wear, and broken splines. Then follow the cable up to the cruise control module. Some cars route the speedometer cable to the cruise control transducer, then to the firewall to the instrument cluster. That transducer goes bad. Thats what happened on my 81 olds. The speedometer would bounce around at speeds less than 15 mph. I replaced that transducer and it is steady now.

Sounds like a broken speedometer cable. The bounce around erratically, because the cable is still connected under the hood and still spinning. Even though its broken the two ends make contact and still causes some movement of the speedometer.

Usually runs from the transmission through the firewall and into the back of the gauge cluster.

check speedo cable for tightness at both ends,1 on trans 1 back of dash.if tight replace the cable,they can bind or strstch in liner causing speedo bounce.

Most likely your speedometer cable is bad. Good luck.

you probably need to replace the cable or the speedo

The "needle at 20MPH" is a sure-fire indicator -- it's the speedometer head. This is a common problem in this year.

I haven't found a fix other than replacing the speedometer head, sorry.

the speedo cable needs to be replaced,they wear out internally and start to jump arounr inside the sheathing

Hi.
It's a common fault with the cables.

If you can take it apart when you remove it, Then use petrol to clean it, let it dry, then use a thin oil like 3 in 1 and re-assemble.

If this still produces the same effect - Replace the whole thing - it won't get better.

(I restore Land Rovers - this is a common fault)