rpms vs nv4500

[powermad]

so the previous owner of my truck swapped in a built nv4500. im running 33 inch tires and am not sure of the gear ratio in the rear end. its a 1997 auto 4x4... i drove by a mph detector and it says i was doing 50 in a 40mph zone. and the speedometer read 40mph. ive also been warned for speeding.. 85 getting on the freeway when my speedo read 65. is it possible for my speedometer to be off that much? how can i fix it?

 

[powermad]

not sure why i wrote rpm vs nv4500...

 

[estrada5.9]

Sounds like you need to do some math

Figure out stock tire size revolutions per mile

Figure out tires you have now revolutions per mile

Figure out the percent difference and ba-da-bing apply that to whatever speed your going

or

Change gear in t-case to fix speedo.

 

[lorendiesel5.9]

You can figure it out on here just click on the HP calculator link at the top of the page.

 

[madmikeismad]

20 off is pretty extreme. With 37s and stock gears mine was 15 high at 70 on the speedo

Sent from my phone.

 

[estrada5.9]

You can figure it out on here just click on the HP calculator link at the top of the page.

Hows peoples gonna stays mart if we yous al dis techknowlogees?

 

[8lugdeezul]

Easiest thing would to just use the calculator on the site, if not you could always get your build sheet.
Contact Dodge

 

[Tpull123]

Here is a picture from my gearing calculator sheet (it made me break it into two pictures). I also have the NV4500, with 33" tires with the 12 valve. It should give you a MPH for each gear and RPM you are at. THere is two columns, one figured with 3.73 gears and one with 4.10 gears, so you should be covered either way:Cheer:.

 

[Big Blue24]

The overdrive gear ratio in an automatic is 0.69. The overdrive ratio in an NV4500 is 0.74.

Your rear gear ratio is likely 3.54 or 4.10.

Most 285/75/16 (33") tires are somewhere between 32.6 and 33.1 inches tall.

Using the above information at the HP calculator on this site, you should quickly be able to calculate speed vs RPM.