I am having speedometer issues:
It is reading a slower speed then the actual speed, it is off by about 7%. The truck is stone cold stock. (Tire size is factory and it has the stock rear)
What I think is happening is:


The VSS on the rear isn't picking up a full signal. I think the rear fluid could be changed and a new ABS VSS pick-up sensor replacement could solve this issue?


This is confusing to me since the VSS is part of the ABS system but I think it is also the signal that sends the speed to the pcm and then to the dash?
This is not an electronic display that can be programed from the dash and there isn't a gear drive on the output shaft of the automatic tranny.
Do you think I am on the right track??????

 

97 should have a speedometer cable going to the trans. The electronic speedo came out in 99.

 

Not true. It's driven by a VSS on the transmission, not the one on the rear.

The VSS gear is on the drivers side of your trans toward the mid/rear, a bracket with a 10mm bolt holds it in place, unbolt and pull out being careful to not damage the O ring. You need to replace the gear with one with a different tooth count.

http://www.transmissioncenter.org/Fo...eter_Gears.htm

 

This one is electronic

 

I thought the one on the tranny was to control the shift (more an input then an output)

 

The one on the tranny controls both the ECM and the speedometer/odometer. Now, I'm finding stuff that says that the V6 is electronic but the V8 is gear-driven. This is 97 and 98 only, 99+ is all electronic.

 

Oh yes, it can be confusing
The tranny was just rebuilt so I know there isn't any gear drives on this one. My logic says it is the VSS on the rea that is the issue. I am thinking the oil has a lot of contaminates in it from farm use with out an oil change. The metal contaminates might be altering the magnetic pick up????
I am going to change out the sensor and old oil and see what happens. If it doesn't correct the speed at least I know I have new clean fluid in the rear.
I love my old farm truck so it isn't going anywhere unless the speeding tickets add up.
LOL

 

I do know for a FACT that the VSS on the rear axle does NOT drive the speedometer. The one on the transmission does, the question is whether it's gear-driven or magnetic.

 

I changed it out anyway and changed the gear oil. The oil had a little water in it.
And as you said the speedometer still has the same issue so I'll try that sensor next.
It still baffles me on why the speedometer would work but not read the correct speed? I get it if the needle is bouncing around or stops working completely. But to be off by about 12% just isn't making sense to me.


Thanks for your help and I 'll post weather or not replacing the VSS on the tranny does the trick
All I can do is remove and replace

 

Before replacing it, remove it and see if it has a gear on it. If it does, get a different gear.

 

You are dead on
It is a gear driven to electronic drive
I'll have to put a small gear in it to speed up the reading on the cluster.
Thank you guys

 

That may fix your shifting issues in your other thread.............

Did the site I linked help you with figuring out which gear to order?

 

It looks like the link will get me what I need. I just need to count the teeth on the gear

 

Mine tooth count is 21 (purple) and that looks like most teeth I can go? The speed is reading slower then the actual speed so I am think I need a smaller gear?
I might have that wrong and I need less teeth

 

Yes, you need less teeth.