I recently had a set of 295/75/16's mounted ony my otherwise stock 97 ram...

I know the newer trucks can be reprogramed electronically, however I was wondering if I could figure out which speedo gear i need and replace that. I know with the Jeeps that use NP231 and 242 t-cases you can. Can I simply get a new gear for my NVG241? If so, how can i figure out which one i need. I have 4.10 gears, 4x4 Auto, tires appear to measure just under 33in mounted on the truck with weight, but manufacturer claims 33.4

Is there chart floating around the internet somewhere I can find out which gear i need? Is the only way to get it fixed to have a shop recalibrate it? Dodge dealer said to take it to a speedo shop.


Any help would be appriciated. -Tim

Edit: Truck came stock with 245/75/16s

 

www.chromewheel.com

 

I had the same problem when i went to bigger wheels.I got on the freeway and ran the five mile speedo test,i was off by 3 tenth's.I went to the local speedo shop and told them how far i was off.They did a calculation and sold me a gear for 20 dollars.I put the gear in using their tools in the parking lot in about ten minutes,now my speedo is right on according to the markers.You may be able to do the same.Good luck

 

Tim,

DC makes a bunch of different gears that will correct the speedometer. You can also get them from Rickson wheels - They'll tell you what gear you need and they tend to have them in stock along with the o-rings. One tip, Don't twist the VSS unit when you re-install it or you'll cut the o-ring and have a potential leak point.

 

Your 97 sounds like it's set up pretty much like my 97...only difference is my spedo has been off since it was new! I'm reading five mph faster at speed. I've tested it several ways. My favorite is those ridiculous "your speed is" radars that the police set up. Usually they are mounted on a trailer and the cops leave them unattended in "targeted speed zones". I have found over several years that my truck and the radar trailers are very consistent- I'm always showing 4-5 mph faster that the radar machine.

I would love to here if you find a simple fix.