2001 peterbilt speedometer help

I just had to buy a new speedometer cause the old one quick working. My old one was a white back 80 mph and the new one is an 85 mph. I set the dip switches according to the chart but it is way way off. At 70 mph according to my gps my speedometer reads on 20 - 21 mph. Can anyone help me. the chart says to set the dip switches as follows 2,5,6,9,10. I have 11 r 24.5 rubber 3.25 rear's and an 18 speed. Thanks for any help in advance.

 

Try setting the dip switches the same as the speedo you took out.

 

i did that as well and i would be doing 30 and the speedometer would be reading 85

 

I'm assuming that the new speedo is a "peterbilt" one. I'ld call a dealer and talk to parts or service and have them figure it out. The new speedo isn't a direct replacement of the original so if they gave you a different one, they should figure out how to set it up I would think.

 

You need to set it for being driven off the ECM. There should be a setting in the instructions to allow for it.

 

My ecm read out on the dash is off by 4 mph as well. so its not entirely correct itself.

 

You need to contact the manufacturer of the speedometer or google them for installation instructions. Peterbilt parts guys don't have a clue how to set speedometers and on an 01 model it won't have anything to do with your ECM. There is a sending unit on the back side of your transmission but it won't run through the ECM. The ECM has no idea how fast it's moving down the road. Just the rpm speed it's keeping.

 

Heavypete if you can send me those installation instructions I could probably tell you how to set it

 

My speedo for my kw was same way has dip swicthes on back when i replaced it i slowly walked up the mph to meet what my tach and gps read. Did first setting by book to get starting point then went up from there. hope that helps you got mine within 1mph.

 

thanks all got it figured out finally.