Odd wire into bottom instrument panel (speedometer?)

[Rangerang]

1990 Ranger: I'm replacing the instrument cluster & I've found an odd tube going into the bottom of the panel into the speedometer just under the 85mph mark.
The replacement cluster has NO fitting for this and I can't see a way to disconnect it.
The white cable has a thumbwheel on it with a tiny wire going into the cluster. It looks like the thumbwheel is meant to adjust the tiny wire. The tubing goes down
to the steering shaft, around it to the driver's side & a right angle turn to go down the shaft into oblivion. What is this? How do I remove it?

Also, the replacement cluster has four tabs behind the tachometer, IGN, SIG, GND, & 8CYL. I have an 8 cylinder Mustang engine so the "8CYL" is of interest.
Is this a separate SIG input or should it be tied high(12V) or low(GND) to make it correct for 8 cylinders?

Reasons for replacement are:
1) Fuel gauge always reads empty, could be the slosh module. I have a rail mounted fuel pump so the in-tank pump is just the sender. It's well grounded (after
some fixes) & is righteously correct. It's all good up to the gauge.
2) The oil pressure gauge (just a switch) bounces & sometimes actually rotates. I haven't checked the pressure switch; it could be intermittent.

I have a breakout box which may only give access to the tach signal; the others are probably direct. But that should be of use to find how to make the tach
good for 8 cylinders.

Thanks for any answers.

 

[RobbieD]

The only thing that comes to mind, from your description, is the linkage for an auto trans gear indicator; as shown here:

 

[pjtoledo]

the thumbwheel adjusts the shifting indicator. the other end has a loop attaching to a bracket that moves with the shifter.

 

[Rangerang]

Thank you, that's it. Maybe my replacement cluster is from a manual trans?
Now, what to do with it? The shifter reads as correct as it will get; I'm missing "D",
it goes from 2 to OD probably due to the swap.
I don't see how the one end goes to the shifter since it goes into the instrument cluster.
I never noticed that the other end comes out at the indicator.

I have the shop manuals but can't quite make out what page you have open.

Thanks.

 

[Rangerang]

Doh, just noticed my replacement cluster doesn't have PRNDL.. Wrong cluster.

 

[Snoranger]

Doh, just noticed my replacement cluster doesn't have PRNDL.. Wrong cluster.

The manual cluster has a blank plate that snaps in place of the PRNDL… just swap it from your original cluster. It should take you more time to read this sentence than it should to swap them.

 

[Rangerang]

I can always use just the gauges.

 

[Rangerang]

Just saw your reply. Looks like a plate at the bottom unbolts & go from there.
Thanks again.

 

[Rangerang]

Found it in my manual under "Steering Column"; NEVER thought to look there. You've made my day.
Thanks you, thank you.