Depends on usage and expectations.
37's with 4.56 almost duplicates the stock 30" tire with 3.73; at least mechanically, it doesn't compensate for the additional rotating mass, rolling resistance, etc.
The above chart is for a 68RFE.
Personal experience?
I ran my current 37s with 4.88, ran terrific when towing, got great mileage, etc. (essentially equal to stock tires on 4.10s).
As an experiment, I dropped back to my prior 4.11s ( same as stock w/3.42); for daily driving - empty, I like the drivability better, 1st is useful, shift points are where i would expect, and it grabs 6th right as im hitting 55.
Still, fuel economy is down by about 4mpg.
It gets better hwy mpg in 5th, LOL.
Keep in mind, im in the PNW, so we rarely exceed 65-70; users in TX/FL, etc., who do 90 everywhere will have a different experience.
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