speedometer reading approx 10mph slow all of a sudden

[black_demon69]

speedometer reading approx 10mph slow all of a sudden (SOLVED FOR NOW)

94 ranger 4.0l 4x4 3.73 gear ratio m5od trans 1354 transfer case.

ok i have made no changes to gearing tire size etc. the only thing i have fixed in last week was the throttle cable..

any input would be nice as i need some direction (i did find tech article but not sure it applies here)

could it be cable dragging or speed sensor? bad speedometer?

i am going to pull gear and check color and wear will post pic when done

 

[ab_slack]

How do you know it is suddenly reading slower? Compared to what reference and was the comparison with whatever reference over extended period before and after?

I changed tires once and Dayton Ohio changed from being 600 miles from here to 660 miles and my fuel economy went up from 22mpg on that trip to 24mpg (good thing since it was a further drive). But you said you didn't change tires.

 

[black_demon69]

How do you know it is suddenly reading slower? Compared to what reference and was the comparison with whatever reference over extended period before and after?

I changed tires once and Dayton Ohio changed from being 600 miles from here to 660 miles and my fuel economy went up from 22mpg on that trip to 24mpg (good thing since it was a further drive). But you said you didn't change tires.

rpms on tach i know where they sit at when traveling at 80 MPH (normally about 2900 rpm at 80 MPH on speedo) currently about 3500 rpm when speedo reads 80MPH

also my GPS unit in my truck

 

[black_demon69]

pink tooth count 19 looks like its got some wear

 

[ab_slack]

if just the tach I would wonder about the tach, or the trans (if auto).

But GPS if it holds consistently different, yes the speedo. GPS speeds sometimes get weird but not for too long usually.

80mph pretty much rules out being stuck in low range. lol

 

[black_demon69]

if just the tach I would wonder about the tach, or the trans (if auto).

But GPS if it holds consistently different, yes the speedo. GPS speeds sometimes get weird but not for too long usually.

80mph pretty much rules out being stuck in low range. lol

update

pulled and checked speedo gear you can see pic above it has a little wear
pulled cluster and cleaned and lubricated worm gear in the back of speedo
pulled speedo cable and cleaned and lubed

speedo now reads about 3 MPH fast which is acceptable and about the way it was however it bounces just a little probably the gear i'll have to see if i can locate 1..

according to some information i found online it should have the 18 tooth yellow gear for the 3.73 ratio. the 19 tooth pink gear is for 3.90 ratio. not sure how accurate the info is though..


80 MPH low range LOL at first thought i had left it in 4th but that wasn't the case it was in 5th.