21 hours ago, BearCreekBum said:

I'm out of ideas.

Looks like you are stuck buying a new mux unit and not sure if it is depends on right or left unit. I know the rear mux is a different part number.

After you get the new one send the old one to @justgary and let him see if he can fix for you to have a spare. He loves to take things apart.

thanks.  I ended up moving the buttons to the left MUX and just unplugging the right one for now.

Bump on this one.  I have a 2008 24 LSV that suffers from same issue. Any updates on this?  Would like to know how much length of cable was needed when anyone did this successfully too.

Plenty of room to open the rear hatch when hooked up. 
 

I would suggest you drive to your Ford dealership and take a look at the Expedition MAX. In my experience, it is a far superior tow vehicle and I would argue nicer interior as well. At least until GM finally introduces the new full size SUVs (which have a front end very similar to the current GM 1500s which are polarizing at best). 

Like UWSKier said, try one of the other plugs in the dash - they all have the same signal.     I'm not sure how to decide if it's bad or not but if you decide to buy another one here is a good price on one:  https://www.bakesonline.com/gauge-speedometer-60-mph-black-white.html

A couple articles for you @DGAZ

the first says for new boats, but is helpful for used as well.

Don’t forget that you may need more than just the boat!

Don’t forget to post pics!! We like pics.