1984 Subaru speedometer has gone awry! Reading 80+MPH while going 30MPH in actuality! Speedo hub at fault?

I found this and I am going to check it out and if I can, I will post the results. Gotta lot going on...  https://www.techsupportforum.com/threads/speedometer-reading-off.181997/

Seal on the transmission side of the cable has failed and it is pumping gear oil into the speedo head. 

GD

Thanks, GD. Tell me it ain't so... I tried to take out the instrument panel once and gave up. Guessing that's on the agenda again, along with a new cable?

You can buy yourself a cell phone holder for the windshield, and then you can download a speedometer app for either iOS or Android. Problem solved if you don't want to mess with the cable in the meantime.

I've got my Tom-Tom for that if needed. Thanks though.

I dug into it. I took the original and carefully pulled the "glass" then pulled the black "separator". Next, I removed the two screws that secure the head and did the same with the donor, eventually replacing the drier head into the original assembly in reverse order. All works now but reads 5 mph slower against a GPS Speedo. Tomorrow's another day...

5 hours ago, lrgvanman said:

... All works now but reads 5 mph slower against a GPS Speedo. Tomorrow's another day...

Usually, it could be caused by using slightly oversized tyres than what the factory specified to be used on that car.

Kind Regards.

That difference could be in the makeup of the speedo. Under the instrument cluster trim panel there will be a statement that says something like 1km = 660 rotations - but probably in miles for you. 

If these are different that’ll be where the speed reading difference is. 

Cheers 

Bennie

Actually the speedo  is okay and spot on with my Tom-Tom and the GPS black box is wrong. Thanks for all your help and suggestions. I took the speed head out of the "new to me" cluster and put it into the original cluster and all is good now.