I know my '78 FJ40 has stock 4:11 gearing in the axles. Anyone know what the stock gearing is on a 2017 4Runner? For how big the owners manual is you would think it would be in there, but nowhere to be found!!!! A pic from today's run up Seven Springs Rd north of Phoenix.
This is a frustration for me. The rear axle is unique to only the 4runner and Prado 150/GX460. It's generally known as an 8.2. It actually IS a larger diff than the 8" or the "8.4", but only a little bit. They seem to be very stout. But there is almost no aftermarket support for R&P ratios. The only options are stock 3.73, stock Prado 150/GX 3.91 (no real point in swapping those), and then jumps all the way to 4.56. So you either have 3.73 or 4.56. No 4.10 or 4.30.
So... that kinda sucks. IMO 4.10 would be ideal and 4.30 would be really nice as well. I think 4.56 is too deep for a frequently daily driver. Even with 285 tires. But that's what you get to choose from unless you want to swap to another axle. Diamond makes a LC9.5 center section housing with all the outers reusing your stock parts. That would open up the range of Diff gearing. But it's a lot of $ for the sake of having 4.10 gears. Maybe sometime soon when Tacoma 8.75 rear axles are getting to junk yards we'll see a swap setup for them. They have 4.30 diffs and internal e-lockers.
The one consideration to think about though is that the RX350 and Highlander have very similar engines, much smaller tires, and have 4.39:1 differentials - but they also have 6 or 8 speed autos with extra overdrive gear ratios. If you work all the math out it's not too far off or 4.56 gears. So maybe 4.56 with taller tires isn't as horrible as it sounds? Not sure.