Maybe it's all in my head, but after making a 3.25 hour trip today, I feel like my speedometer is inaccurate around the 70-90 mph range. The lower ranges feel right, but when I get it up to 70 and then accelerate from there, the speedo will read 90, but it really doesn't feel like I'm doing 90. I mean, I had a bunch of other people going "90" along with me and I really don't think that's what was going on. Is it possible for the speedometer to LOOK like it's working, but be off?

I haven't changed tires or wheels, but I HAVE removed the instrument cluster (about a month ago) while installing my remote start unit. I'm thinking that maybe I did something to that little cable that runs down alongside the steering column?

 

Also, I just did the instrument cluster diagnostic test (hold down the trip button while you turn the ignition on) and I don't think it was trying to tell me that it noticed any problems. hehehe...the test was pretty cool...went through some steps and then the needles all moved in unison...kinda fun. Anyway, I don't know what it does if it thinks there's a problem, but I don't think it tried to tell me that.

So could this still be happening, or is it all in my imagination? I'd like to know before I enlist someone to drive alongside next to me going 75+ mph to see what's up. Thanks, y'all!

 

around here, on I-95 going to florida, a big truck like ours doing 90 would be nominated to lead a convoy, guess you were shaking the trees.....

what did overhead console say for MPG?
my 4wd slurps diesel above 75mph....i rake the leaves!

best way is mile markers & stop watch,
or cell phones with another car
hth?

 

To test your speedometer drive at constant speed over a marked one mile coarse, use the mile markers, and time it in seconds.
Divided the number of seconds into 3600. This will give you your actual MPH.

I try to do it over 3 to 5 miles and I get a more accurate reading. But when you do this you must divide the seconds by the number of miles first.

If you know someone with a laptop and a GPS receiver then you can get your actual MPH that way over a much shorter distance.

Radar also works. Just make sure you know the person holding the gun!!!!!!!!!!! .

Good luck.

 

HAHAHA! Yeah, that's what I'm saying...I don't think I was really going that fast. Sure, I sometimes roll going 84 (and even 89 at times), but this felt more like 74-79, but my speedo said more like 92. Odd. I'll try the mile marker timing trick.

 

what was your tach at?? if you were around 2200 you were prb doing 70-75 but if you were around 2750 rpms I would say 90+ but that is with mine I have 3.5 gears.

 

Well, I did some quasi-scientific testing last night and here's what I came up with. See if y'all can figure out what I should do.

Shown Speed........Actual Speed
67.5 mph...................66.6 mph
80 mph......................77 mph
85 mph......................81 mph
90 mph......................85.7 mph

Now this may not seem like that big of a deal, but since the dang cruise control on these trucks only lets you set it up to "85 mph", that means I can only go 80/81 mph and use the cruise. Speaking of which, is there a way to override that cruise control governor?

What should I do about the speedometer being inaccurate? Am I expecting too much accuracy out of this instrument?

 

You'll never get one of those fancy little pieces of paper with all the writing on, and the you owe this much at the bottom

Unfortunatly, mine goes the other way at 60mph on the spedo I'm doing 68 per the little screen readouts along the road.

Rick

 

Anybody, anybody?

 

Well, it looks like, from your numbers that the difference is incremental(?)

.9
3
4
4.3

The speedometer is all electronic.

I think the simplest solution would be to get a 1/2" to 1" smaller tire.


phox

 

If you are still running stock or the same size wheels and tires the speedo should be nearly correct.

I think your problm could be corrected by a reflash but not 100% sure, or a different gear on the sending unit. Something you should talk to your dealer.

Mine reads one mph over actual speed above 25 mph up through 75. Haven't tested it above and below those speeds. I am using GPS to verify my speed now but will not take my eyes off the road at high speeds when I do exceed 75. and below it doesn't matter.

 

You guy use the speedo??? I replaced mine with a radar detector a couple of trucks ago.
You do have a valid point though that the dealer owes you warranty if they use your odometer to determine it's duration. I can remember people suing for gettin tickets because of uncalibrated speedo's in my hometown before. Don't know if they ever got anywhere though.

 

My truck sets the cruise at 90.

 

well, look on the bright side of it ! maybe your odometer is clocking less miles than actual too i don't have the answer to your problem--just wanted to add that my truck originally had 245 75 16 tires and ive been running 285 75 16 tires for a long time and every time that i pass a radar equipped sign or use a buddys gps it never reads inaccurate.

 

You can go to the dealer to get a reflash under warranty if you need to but u r putting less miles on the truck This way.