Was having issues with my speedometer jumping around after hitting about 55-60 mph when the outside temperature was cold, not as bad when the temperature started warming up, mainly summer. After things warmed up mechanically, it would settle down some. Replaced speedometer cable and gear on the end of cable, but still doing the jumping, just 2 or 3 mph instead of the 10 or so mph before. On a couple of occasions while set on cruise of 65 or 70, would jump to like 75 and just stay there until slowing down. Could the speedometer itself be bad or also was told there was another gear in the tail housing of my auto that the other gear set into. Any help would be appreciated.

 

What year Ranger?

 

Sorry, its a 94

 

Yes, there are two gears

"drive" gear is on the tail shaft, it is a worm gear, it is held in place on the shaft by a ball in a "hole", the worm gear has a slot that slides over the ball

The "driven" gear is the one you pull out and change to calibrate speedometer.

Drive gear is not all that hard to replace, you drop the driveline, then remove the large flange nut, it is on very tight, thats the hard part
Pull out the seal and you will see the Drive gear, you can push it out via the speedometer cable hole.
You do need a new seal but they are not expensive.
I have never done one on an A4LD 2WD automatic, so you may need to pull off the tail shaft housing, which isn't that bad either

Ford speedometer Drive gears look like this: http://htsmall.dearbornclassics.com/...u/64-36372.jpg
Or this: https://i.ebayimg.com/thumbs/images/...kEd/s-l225.jpg


But what I would do FIRST...............
get a reversible drill and hook it to the speedo cable, I can't remember which way it turns, but turning it backwards won't hurt it, you do that every time you drive in Reverse, lol.
Any way run the drill up to high speed on speedo and see if it is rock solid or wavering.
If it is solid then you will be changing the Drive Gear
If wavering then speedo is the issue

 

Okay, so what you are saying, I need to hook a drill to the speedometer cable on the transmission side and give it a good spin. Can't recall, but do I need to take gear off to access that end of the cable?

 

You can leave gear on and spin it with the drill just be careful not to damage the plastic shaft or you will have to replace the gear

 

Okay, thanks. Will try that first, plus I have several gears as spares.