So I was driving on the highway today and everything was fine up until about 40 mph. At that speed and above my speedometer started making a whirring noise and the pointer started wiggling back-and-forth by about 15 or 20 mph back-and-forth, back-and-forth.

I pulled the speedo gear from the Dana 20 and it looked tight with all the gears in tact and then I pulled the speedometer and it looked and felt like it was attached correctly also. I thought it might be loose but it's tight.

Any ideas or experience with a jumpy speedo?

Pull the speedo cable and lightly grease it. Should take care of the problem.

How do I grease it?

Disconnect both ends then gently pull on the interior cable on the end that was connected to the TC. The cable will pull out of the sheath. Clean it with brake cleaner. Set yourself up with a little grease on your hands and as you are reinserting the cable back into the sheath, apply a little grease to the cable as your pushing it back in. Re-connect the speedo ends.

Awesome, I can do that.
Thank You!!!

Ok, I disconnected TC side and speedo side and backed it through the firewall. I pulled the cable out from the top, cleaned it off, sprayed some WD down the hole to clean that out.
Gloves on, squirted some grease on my glove and fed the wire from my glove back into the hole till it popped out the bottom.
Connect the top, connect the bottom.
Thanks again!

Working ok now?

Yep! Went to A&W and treated me to a Rootbeer Float!
Looks like I owe Moab Mike 1 too!
THANKS!!!

Huh, I'll have to give that a shot. Thanks, mike!

The only part I had a little trouble with is when pushing it down from the top, and the job was almost complete, the last couple inches kept getting hung-up (at the transfer case end) and I couldn't push it through by hand... I had to grab it and push it down with pliers and it popped right out.