Dip switch settings on a 379

Oh dear - I’m in the same position.
Old school 80mph speedo.
Changed rears from 3:70 to 3:55 24.5 LP.
Speedo reads 65 when running 70.

Amtek calculations were no good.

Old dip switch settings were 2,4,5,7,8,9.

Any ideas?

 

Ok, got it figured. @mtoo - charts are the fix!

Started at 690 ish, stopped and adjusted 6 or 7 times, until GPS matched dash.

Moved in increments of 7 steps at a time.

Thanks!

 

Thanks for this Chart helped me today. Got my new to me speedo spot on.

 

I'm thinking mine is 662HZ but how do I find my overdrive ratio to confirm? Does anything need to be changed in the ECM with Electronic Technician? It's a 95 KW with the 80MPH all analog speedo but electronic engine (3406e). Nothing digital on the gauge. 3.55 rears and 13 speed. Switching from LP24.5s to taller 11R24.5 on Monday.

 

I have an E model CAT. Do I need to change any settings in the ECM? Or is it all done with the dip switches?

 

That is the same ratio trans and tires I’m running. I used the chart to get it right after going from a 15 over with 3.36’s to this set up. I can’t remember exactly which one I used but it was way up the chart toward the faster ratios when I finally got it dialed in.


The ECM won’t affect your manual speedometer. However you need to change it in ecm so that the speed it reads and miles it logs remain correct.


A 13 speed is .73 overdrive may be why I had to move way up the chart I’m not sure. I was glad to have a starting point though

 

Thanks. Do you remember where the PPM setting was in Electronic Technician?

 

When I replaced my speedo it came with a guide for the switches. Have you tried googling the dip switch guide. Several come up. Also contact a speedometer shop and see if they can help you.

 

I ended up using the directions from the Ametek 900 series Speedometer and it's spot on. Very easy. All the numbers are in the formula. Just use your gear ratio and tire height to do the math. Now I need to find someone with ET that won't rape me just to update the PPM in the ECM. The dealer wants to bill me for an entire hour for a 5 minute job.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.ametekvis.com/-/media/ametekvis/download/technical-support/900_series_speedometer_calibration_switch_settings.pdf?la=en&revision=045e282a-22ad-4eab-bfb6-5b552e8f8145&hash=9329DC6289E3DBE7E013DDF08D63AA20&ved=2ahUKEwjXmsL4yt7xAhUEV80KHS1lBK8QFnoECAQQAQ&usg=AOvVaw2scjlEf-Mxg4EMiFF5kgdg