speedometer inaccuracy

[TagAllen]

I don't recall if the speedometer was inaccurate before I swapped the 4l60 for the 4l80. Does the vss from a 95 4l60 give the same type/speed signal as a 96 4l80? Such as number of pulses per mile? I do know the vss looked different from one trans to the other.

 

[someotherguy]

Yep, same pulses per mile. How inaccurate is it, and is it fairly consistent across the range?

You're a 1995 so it's the last year you can easily DIY mod the DRAC to recalibrate the speedometer. A little more work to dig the DRAC out from its hiding spot under the PCM's shelf behind the glovebox, but it's still easy to get to. Little white plastic enclosure a bit smaller than a deck of cards, under the black plastic PCM bracket.

If you have re-geared, or different size tires from stock, you'll need to do this if you want accurate speedo. Pretty easy work if you can do simple electronics soldering, and it's literally just a couple bucks in parts for the DIP switch(es).

Richard

 

[TagAllen]

I actually have a adjustable buffer. I purchased it because I thought my tires were causing the inaccuracy. I checked my rear gears and my tire size and set it to what I thought was correct and it still came out the same amount of inaccuracy as the stock buffer. I believe it is about 8 mph off at highway speed I don't know if that is constant at town speed.

 

[Raspi454]

My 98 k1500 305 4l60e is reading about 5mph more than I'm actually going and it's bothering me. Did it when I bought the truck, and still does it, after just having the trans rebuilt last week. Any help would be appreciated. Afaik everything is stock

 

[Erik the Awful]

Buy a slightly smaller tire next time?

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tiresize.com

 

[vort97]

Yep, same pulses per mile. How inaccurate is it, and is it fairly consistent across the range?

You're a 1995 so it's the last year you can easily DIY mod the DRAC to recalibrate the speedometer. A little more work to dig the DRAC out from its hiding spot under the PCM's shelf behind the glovebox, but it's still easy to get to. Little white plastic enclosure a bit smaller than a deck of cards, under the black plastic PCM bracket.

If you have re-geared, or different size tires from stock, you'll need to do this if you want accurate speedo. Pretty easy work if you can do simple electronics soldering, and it's literally just a couple bucks in parts for the DIP switch(es).

Richard

Is it much different for a 97??? I have instructions and swich setting chart,, but you just made e wonder,,,,and to begin with,, cant imagine why it would be off by 20 90@ 70.

 

[df2x4]

Is it much different for a 97??? I have instructions and swich setting chart,, but you just made e wonder,,,,and to begin with,, cant imagine why it would be off by 20 90@ 70.

'96+ don't have a DRAC. As far as I know the speedometer reading is 100% controlled by the PCM in the '96+ trucks. For your '97 you'd need to find someone with JET DST or TunerCAT software to modify the tune.