Run 4.88 gears if you put 33s on a 5th gen 4Runner, and 5.29 if you go to 35s. The factory 3.73 (V6) or 4.30 (some packages) ratio leaves the 1GR-FE V6 hunting for gears and the transmission shifting constantly once you add tire weight and diameter.
The 5th gen 4Runner uses an independent front suspension with a clamshell front differential and a solid Toyota 8" semi-float rear. Both ends carry the ring and pinion, so a re-gear means setting up two differentials — and the IFS front clamshell is one of the more demanding setups to get a correct gear pattern on. This is not a first-time differential job. If you have never set up gears before, pay a shop that has done Toyota 8" clamshells specifically.
The reason you re-gear is tire diameter. Stock 4Runner tires are roughly 30–31" tall. Going to a 285/70R17 (about 32.7") or a 285/75R17 (about 34") drops your effective gearing and forces the V6 to work harder, especially in the higher-altitude climbs around Phoenix and the Mogollon Rim. A 33" tire on factory gears feels noticeably sluggish and the transmission downshifts on grades it used to hold. Re-gearing to 4.88 restores the factory drivability you had on stock tires. For 35s, 5.29 is the right target.
You probably don't need this if you stay on 32" or smaller tires and mostly drive pavement — the penalty is mild and the cost is real. Re-gearing makes the most sense once you are at 33"+ and using the truck off-road regularly.
A complete re-gear needs a ring and pinion set for both axles in the same ratio, a master install kit (carrier and pinion bearings, crush sleeve or solid spacer, shims, seals, marking compound), and the setup tools: dial indicator with magnetic base, a press for the bearings, a case spreader for the front clamshell, and an inch-pound torque wrench for pinion preload. Budget marking compound and patience for multiple pattern checks per axle.
1. Drain both differentials and remove the carriers, recording existing shim thicknesses as a starting reference
2. Press old pinion bearings off; press new races into the housings
3. Set pinion depth using the master kit's pinion shim, then check the gear pattern with marking compound — adjust shim until the contact pattern is centered on the tooth flank
4. Set pinion preload with the crush sleeve (rear) or solid spacer plus shims (preferred for repeatability) to the inch-pound spec
5. Set carrier bearing preload and backlash (0.005"–0.008" typical for the Toyota 8") using the side shims
6. Re-check the pattern under load, confirm backlash, then reassemble
7. Repeat the full process on the front clamshell — the case spreader is required to seat the carrier
8. Refill with the correct gear oil (75W-85 or 75W-90 GL-5; add friction modifier if running a clutch-type LSD/locker)
The front clamshell is where most home setups go wrong — the pinion depth and the spreader procedure are unforgiving, and a bad pattern howls or fails early. Always match ratios front and rear exactly; a mismatch binds the drivetrain in 4WD and destroys gears. Break in new gears gently: 500 miles of varied driving with no towing and a 30-minute cooldown after the first highway run, then change the oil to flush break-in metal. If your 4Runner has an electronic rear locker, re-gearing does not affect it, but confirm the carrier you keep is correct for your ratio split (most 8" carriers cross the 4.88/5.29 break, but verify).
Gears and a master kit run about $800–$900 in parts for both axles (Nitro Gear 4.88 set around $540, master install kit around $280). Professional setup of both differentials runs $900–$1,700 in labor depending on shop, putting a turn-key re-gear at roughly $1,400–$2,600. DIY drops it to parts cost plus tools, but the clamshell setup risk is real — a botched front pattern costs more than the labor you saved.
| Part | Vendor | Est. price |
|---|---|---|
| Nitro Gear 4.88 Ring & Pinion Set (Front Clamshell + Rear 8") | Nitro Gear & Axle | ~$540 |
| Nitro Gear 5.29 Ring & Pinion Set (Front + Rear) | Nitro Gear & Axle | ~$560 |
| Master Install Kit (front and rear, bearings + shims + seals) | Nitro Gear & Axle | ~$280 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.