what year 4R and what size tires are you running?
are you happy with new gearing and RPMs on the road?
I'm planning in 4.88 on the '21 Taco.
Here are my 4R specs...
Tires:
Current = 285/70R17 K02 (specs out to 32.7")
The stock 2018 4R I believe would have been 31.6". IMO a 4.88 regear would be a bad match for that stock tire, especially for mpg. I've always ran with the ~33.
Diff:
Current = 4.88
Was = 3.73
2018 4R trans ratios (stock 5-speed):
3rd gear 1.400
4th gear 1.000
5th gear .716
RPM vs gear and road speed on ~33" w/4.88 regear (from 3.73)
3rd @ 45 mph = 3160 (was 2415), 745 rpm gain
4th @ 55 mph = 2758 (was 2108), 650 rpm gain
5th @ 65 mph = 2334 (was 1794), 540 rpm gain
The 4.88 and ~33" works well for me especially when towing the 3000 lb. patriot up a hill. The 2700-3200 RPM range seems to be the sweet spot power wise depending on grade. So 3rd and 4th gears are hitting that range.
Regarding cruising in 5th gear, it's still a useful OD gear and does not hunt excessively between 4th and 5th on slight throttle change. However, if you have that ECO meter/gauge thingy in your cluster, it's not going to be in that happy range as frequently.... unless you are running larger than 33".
Lastly, 1st gear is short lived starting out from a stop. If you are very light on the throttle you'll be in 2nd gear mid intersection, perhaps 3rd after fully crossing the intersection. First time I pulled away from a stop light when I left ProGear, I almost rear ended the guy in front of me. Had a bit more spring in its step than what I was prepared for.