Having a 4-speed automatic with a 3.55 ring and pinion have had me contemplating how to go about alternatives that would provide better fuel economy.
My first thought was to swap out the 3.55s for taller 2.73s but which would significantly lower my cruising RPM, but would also make the engine work that much harder off the line.
I'm worried it would trade better hwy mileage for potentially worse performance in the city. So, this got me to thinking about the possibility of swapping the gears in conjunction with a swap to a 5 speed manual.
I've put together a comparison of cruising speed RPMs between different setups and the total gearing ratios. (Current setup in red)
If I did a swapped to a 5-speed with 2.73s I would only lose about 8% of gearing in 1st with the differences between 2nd and 3rd being negligible. It would also further reduce cruising RPM in 5th gear.
To put in perspective, doing the 2.73 swap along would result in a 23% reduction in gearing.
Thoughts?