Bigger tire and Gear Ratio question.. Please help
Dear All Jeap owners,
I'm new to this.. I have 2011 Jeep JK unlimited 4 door Auto. Just replaced stock tires and wheels(255/70R18) to 315/70R17 and new ATX wheels size 17". Still have Stock Gears (3.73). Please help me to understand this.. Do I need to regear and go smaller.
After fixing my tire size using Superchip flashcal to 34.50" and my speedometer is showing correct speed.
I noticed the current Gas millage is 14 miles/Gal in City. I didnt try the Highway drive yet.
Today I took Jeep on highway and using cruise my RPM on 70MPH was showing around 1800 RPM, but after driving few miles may be 7-8 miles the RPM increased to 3,000 ?? Is it called down shifting? If yes then why after 5-10 miles .
While increasing speed to 70 MPH the rpm increases to 3,000 RPM and the stable at 1800 for around 8 miles before it goes back to 3,000 RPM.
Please explain me about this behavior.
second do you think if I go for re gearing, Jeep will give me better Millage ? in City and Highway both ? is 14MPG bad in city after the bigger wheels?
What should be a good gas millage with this setup on Highway?
Thanks in Advance..
Note: I have already purchased a Yukon 4.88 Gears but didn't install yet .. waiting for your advice..
Last edited by anjum69; 05-03-2013 at 09:41 AM..