Quote:
Originally Posted by 98frontier
Hello, this is my first post as I just registered today, I was curious to know what kind of mileage increase I could expect if I were to install a 3.54 rear axle in my 1998 Nissan frontier in place of the 4.33 axle I have now, my engine is a stock 2.4 Dohc with a four speed auto, my truck is 2wd and I am running 235 75r15 tires in place of the factory 215 65r15.
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That is an 18% drop in rpms. Try reducing your speed by 18% (if you normally drive at 60mph, drive at 49mph) and see if your tranny is happy staying in your top gear with the converter locked up. If it is keeps downshifting or unlocking the converter, you will waste more fuel than if you left it as is.
This isn't a perfect test, since you will have higher loads from aero drag at the higher speed, but it should at least give you an idea if you can stay in your top gear with the higher geared axle.
Oh, picking up an Ultragauge would be a great idea. They are inexpensive and will tell you RPMs, instant and trip mileage, and a bunch more. The Torque app and a Bluetooth OBDII adapter also work well if you have a smartphone.