285/75-16" no intentions of going taller, If you think you might go 4.88's. Who I bought front diff from went taller and 4.88's.

I know gearing questions have been beaten to death on here, but I have a question I can't seem to find a conclusive answer to. I just bought an '02 SR5 V6 4WD automatic that has stock 15" tires on it. I want to move up to at least 31" tires because the 225/75R15's look pretty pitiful.

I don't plan to do much off-roading with the truck. It's most likely going to be my daily driver. I did the spin test and concluded I have 3.73 gears. From everything I've read, only 2WD 4Runners had 3.73. I was expecting 3.91 or perhaps 4.10. Have any of you ever seen/heard of a 3rd gen with 4WD and a v6 having 3.73 gears?

I just bought some used 17" wheels that came off a 2010 4Runner. I was thinking about getting either 265/65R17 or 265/70R17 tires. Now that I know I have the highest gears, I'm wondering if I should stick to a more modest size in the 30-31" height, maybe something like a 245/70R17 (30.5").

Here's a picture of the style wheels I picked up (for $50!):

4 cylinder 5 speed 4x4 elocker got 4.56 (ultra rare) and 4 cylinder automatic 4x4 16" wheels got them too, can't confirm yet but 15" wheels might have got them.

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So V6 Auto 4X4 but it had 15" wheels and 225/75R15? That's a super odd combo. My 4 cylinder 2wd 5 speed with 15's came with a 3.73 rear diff but I've seen no indication that a front diff with 3.73 ever existed until now.

Regardless a set of stock 4.10s would be all you need to make it very close to right with anything from a 30-32" tall tire. Stock diffs can still be had regularly for 100$ a piece.

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I know 4.10s would be optimal for stock 31" tires, but my real question is whether there are any major downsides to using my current 3.73s with modestly larger tires. I wonder how noticeable the power loss will be. I'm not really looking into re-gearing at the moment.

I haven't put the new wheels on yet, so I'm wondering if it's worth it for a purely cosmetic upgrade. Sounds like very few people will have experience running 31s on 3.73 gears since my combination is so rare.

It's going to be subjective either way. I can say I'd personally be fine with it more than likely, but would still spend the 200$ and a few hours to make it "right". I run 35" tires on my Tacoma that's got an automatic and 4.10's and it doesn't really bother me, a lot of people on here would be a different story.

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I guess there's no real harm in putting the 31's on and seeing how it drives. I can always pop in some 4.10s in the future. Where's the best place to pick up some 4.10 front and rear diffs?

Search Craigslist for local partouts Facebook marketplace, local junkyards. They're everywhere in my area I could find probably 10 sets within 30 miles right this second.

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My V6 2wd Auto came has the 3.73 gearing. I am running 31” KO2 and it’s kinda doggy when you accelerate. It’s not really bad but you can feel it. I leave the OD off when driving around town. It actually saved me a bit of gas and better throttle response since it doesn’t drop into 4th gear.
But I do have a new diff with 4.56 gearing and a Yukon locker from ECGS waiting at home for install. Can’t wait to get some free time!!!

So you’re saying turning off overdrive saved you gas? How did staying out of 4th gear get you better mpg?

With OD off I am not mashing down on the gas in 4th to keep that speed going. Ya, the rpm is lower but the pedal is further down. On the fwy, ya OD is on of course. This is just something I noticed in my truck with 3.73 gearing.

Trying to accelerate when the torque converter is locked at 1500 RPM's is going to be a bit of a drag. No power down there so it will waste fuel.

You sure you don't have the 3.90 gears? Anyway, I did the opposite while I was in process with my 4WD swap. I put in the rear 4.10 diff while I still had the 29" tires. There is definitely a large change in performance and highway RPM. You'll probably want the OEM 4.10's once you step up to the larger tires - but luckily there should be a ton of 4.10's out there and available for you.

You will probably also want to get some sort of speedo calibrator (I used one from Dakota Digital). The speedometer is driven off the ABS system, so changing your tire size (but not diff ratios) will affect the speedo.

-Charlie

Charlie,
I did the spin test with a co-worker here at my shop. I counted the driveshaft rotations while he counted the rotations on the tire. He spun the tire 20 times and I counted just over 37 rotations of the driveshaft.

I may do it again today to double check. I can't find a single source that says 3.73 was an option on any 3rd gen V6 4WD auto 4Runners even with stock 15" wheels. I should have 3.91 according to every reliable source I've found.

I may be buying some 245/75R17 tires this weekend to go with the 17" 5th gen wheels I picked up. These tires are 31.5" tall but obviously narrower than the stock 265/70R16 31's. Think I will be ok with this size. Is a taller tire harder to turn than a wider wheel like say a 265/65R17?

No, that's no problem. You will notice the lack of brakes... The 16" wheel trucks have bigger front rotors and calipers and bigger rear wheel cylinders. I still need to upgrade my brakes, especially since my wife daily drives the 4Runner sometimes...

It is also possible somebody swapped a rear diff and not the front. Do you get any binding in 4WD on hard surfaces driving in a straight line?

-Charlie