I have a 1997 Ranger with a 2.3l engine and a 5 speed trans. I recently purchased it and found a couple of the gauges were not working. I replaced the complete cluster with one from a 2001 Sport Trac. It solved all the issues I had except one: The speedometer and Odometer are erratic. This is the same issue I had on the original cluster. It will register 20MPH when you get up to around 35mph, but never goes over 20mph. I have replaced the speed sensor, and the plug that attaches the wiring to the sensor. No help there, still does the same exact thing. So, I am at a loss what to check next. Any help would be appreciated!

 

It could be the DRIVE gear inside tailshaft housing is worn down, on a manual transmission this worm gear is changeable, its 7-tooth

What did the DRIVEN gear look like when you change the VSS sensor unit?
Was it tight on its shaft, can't slip

 

The gear was nice and tight on the shaft and the teeth were all intact and did not appear to be worn.
This is a 5 speed manual trans. Would it have to be removed to replace the gear in the tailshaft?
I can do OK using the tach for my speed, but HATE when something is not working correctly!

 

No, just the tailshaft housing needs to come off, but.................

Did speedometer work before the cluster swap?
If it did then replacement cluster has the issue

There is just 1 speed signal wire from VSS to the cluster, speedo/odo share that signal, its a grey/black wire on pin1 of center connector(12 pin connector)

Same grey/black wire is also connected to computer and cruise control
If you have cruise does it work?
If you have an OBD2 reader see if you can watch speed signal the computer is seeing?

Bluetooth OBD2 reader is under $15 and works with any vehicle 1996 thru 2023 so not a bad tool to "have in the box"

1997 Ranger diagram below
You may want to check that connection on new cluster first before looking at transmission gear as those rarely have issues

 

The speedometer did exactly the same thing prior to the swap, so I think I can eliminate the cluster as the cause. The sensor has two wires going to it and I have replaced the connector end for the sensor on these wires (mostly because I broke the two retainer clips that were VERY brittle) No cruise, just a very basic truck. When I had the cluster out prior to replacing it I cleaned the connections on both the cluster and the harness connectors as well as inspected them closely for any damage.
I am very much leaning towards the gear in the tail shaft as the truck has 300K+ on it. As far as I can tell the trans case has never been opened.
I will look into the OBD2 reader as well. Thanks!

 

OK

Just to be sure you can used a drill on the driven gear and spin it up, and have some one watching the speedometer(key ON) to make sure it goes up with drill RPMs, and past 20MPH, lol
Can't remember which way it spins for speed signal, clockwise or counter clockwise, but doesn't hurt anything to spin it backwards, you do that each time you back up, but speed will only register on speedometer turning in one direction

You have an M5OD-R1 transmission aka M5R1

DRIVE gears are not expensive, seen here: https://www.allstategear.com/M5R1-Sp.../m5r1-169w.htm

There is a small ballbearing in a hole in the output shaft, it usually won't fall out when you pull off the old gear, but be aware its there and if it has come out then that may be why DRIVE gear is slipping
In above link you can see the slot where ballbearing sits in the gear

You do need a jack to hold up transmission/engine since you have to remove the rear transmission mount to remove the housing, take the cross brace out