Speedometer problem

Hey everyone, I have an 86 Wagoneer. (yes with wood siding).
Driving home the other day my speedometer started jumping wildly and making a lot of noise. I disconnected the cable under the dash where the cable attaches to the "stub" cable coming out of the back of the speedo.
I have a couple of questions....
First: I do have cruise control(never worked) and there is round plastic thing that goes between the speedo "stub cable" and the cable coming thru the firewall with 2 wires coming out of it.
Is this a sensor for the Cruise control?
Second: Has anyone ever had this happen to them?

I apologize in advance if this subject has already been covered but I did a search and didn't find anything.

Yes that's the speed sensor for the cruise control.

I had the mechanical speedometer cable on my 87 go bad and it started jumping the needle all over the place before it just broke and I had to replace the cable.

tlman said:

Yes that's the speed sensor for the cruise control.

I had the mechanical speedometer cable on my 87 go bad and it started jumping the needle all over the place before it just broke and I had to replace the cable.

Click to expand...

I've pulled the cable out and it "seems" to be OK.
Could it be I need to just grease the cable?

Lubricating it with light machine oil might help. Mine completely separated and I had to replace it though. You might have to do the same, it is pushing 20 years old after all.

tlman said:

Lubricating it with light machine oil might help. Mine completely separated and I had to replace it though. You might have to do the same, it is pushing 20 years old after all.

Click to expand...

You know, I hadn't thought about that. 20years old and all.

Did yours make noise when it bit the dust?

It could also be the gear in the transfer case bit the dust or has somehow come out of mesh.

woodnjeep

There is a TSB in the back of my 88 XJ manual about speedo cable noise and needle bounce. The TSB has you reattach the to the brake lines with a wire tie instead of the control arm bolt with the clip on the cable.

I went to the dealer and ordered a new cable in the past 2 months for my 88 XJ. The new cable came with instructions and told you how to fix the problem. The instructions with the new cable were a little different from the TSB included with my manual.

The new cable for a XJ with cruise was less than $35. i have cruise so I have a two piece cable, I purchased the lower half. If you don't have cruise then you buy the entire cable.

I also talked to my dealer mechanic and he suggest you play with the cable, you know move it up and down as you sit in the driver's seat, that will fix the needle bouce alot of the time. I just have not had time to try that.

HTH

Martin

I used wheel bearing grease on my cable. It worked to stop the wobbleing. However since then it's come back, must be all that nasty sandy mud we've got around here....

Wheel bearing grease is a bit too heavy for a speedo cable, but machine oil is way too light. I would suggest trying a light coating of regular (lithium) chassis grease reduced slightly with oil.

OK, so now I have a lot more to work with than before.
I knew asking the question here was a good idea.

Now if the weather would behave.
Just got my Rusty's HD Trac Bar mount and 6 inches of snow.
Along with freezing rain and below freezing temps.

A friend of mine who works at a machine shop got me a tube of grease that he says is specifically for speedo cables.

But I'll also check everything that everyone here has suggested.
Especially the position where the cable is tied down.
Thanks for all the advice.

Hoping to get this all done before the weekend. A bunch of us are going to Silver Lake sand dunes in Muskegon and I'm hoping to have everything ready by then. If not I'll have to take something else.
Cherokees (or Wagoneers as it is in my case) are so much nicer on road trips.
Again Thanks everyone, keep sending suggestions if you think of anything else and I'll let you know how it all comes out.

OK everyone. I went through and checked everything that you all suggested and it seems to be corrected.

The cable was attached to the control arm just like martin said.
So I repositioned that to the brake with a couple of zip ties.

And believe or not Mopar makes grease specifically for Speedometer Cables.(when I get a chance I'll take a pic and post it.)
A buddy of mine actually has a tube of this stuff. (He restores old mopars)
And according to him the cable was too dry. So I greased it up and reinstalled. Initial results look good but I only went around the block and haven' t gotten it to highway speed yet.

I check the Gear at the tail shaft and it looks OK.Thanks to everyone for all your advice.