V6 engine issue, I think??

Then why does my speedometer sayes im going 70 and my GPS sayes im going 72, please explain .

 

My truck is stock, my gps matches right up.

 

thanks for the input guys....thought i might of need a tune up or re-gearing...

 

Regearing will not affect your speedo, only the ratio between how fast your drive shaft is spinning and how fast the axle spins. You need to have a dealer take a look at your other issue if it really is a problem with the truck.

 

Gearing. Tire size. Speedometer Calibration. Take your pick.

 

ALL speedometers are a little bit off due to the analog nature of it. Every one reads just a little bit different. I used to work as a technician that made aftermarket speedos and other stuff for cars. I forget what the specs are but SAE specs allow a small deviation in the readings.

 

For speed, GPS is one of the most accurate device you can get.

It uses doppler shift by using the satellite signal carrier waves. Like police radar gun which it uses its own laser.

GPS never transmit information. They're only receivers.

Every 20 minutes, they may download almanach if needed, but otherwise, it uses satellite signals only, which they are already present (satellites always transmitting it).

You need a module to transmit information, usually by cellular (like cellphone), and this is used to record speed or position, like some paranoids parents that put GPS devices in son/girl's car.

You can also use satellite signal to transmit your position when your are in woods far far away, where cellular isn't reachable (ie: SPOT device).

Because of doppler shift method, steep grades doesn't affect speed measurements.

Easy to verify: initialize your max speed data in statistics page. Drop your GPS on something that won't break it apart and see the results

Tried on a 8% steep grade and speed reading on my GPS was accurate, meaning that speed difference was same between GPS and speedo.

Accuracy is around 0.12 mph according to the studies.

US Army use GPS to know the speed of missiles. Soldiers also used civilian gps devices during "desert storm" war (around '90). During that time the S/A was deactivated. Military GPS weren't available at that time and were overpriced.

Planes uses GPS and also other measurements devices.

Speed reading delay is 1 second for low end GPS receiver. However, you can notice a delay or inaccuracies during hard acceleration or hard stop (sudden speed changes), but in those situation, you don't usually read your speedo/GPS, you're concentrating on the road.

Speedo in cars are rarely precise. Example: going from 35 PSI to 30 PSI can affect your speed reading.

 

NTSB. up to 4% off. Dealer gave me that line and then I looked it up. My speedo is Fast. 70 is 64. Just gets old going from my truck to my car. My car is spot on.. When it is time for tires I will just go up one size and that shooed help some.

 

My speedo is off by about 2mph when compared to my UltraGauge, and that's reading direct from the truck.

 

My truck speedo is faster by anywhere from 3-5 mph compared to gps. The faster I go the bigger the difference. My 99 Dodge Durango was almost right in line with the gps.

 

^ This. It's common for the Tacoma speedo to read fast due to the digital to analog conversion (reads 65, actual speed 61: reads 43, actual speed 40, etc...these are mine with stock tires/gearing using radar).

BTW, the FSM lists the acceptable error for the speedo: