The 1999–2000 Toyota 4Runner 4WD with the 3RZ-FE 2.7-liter four-cylinder (chassis family RZN185) is the facelifted phase of Toyota’s third-generation mid-size SUV. It sits below full-size body-on-frame trucks and above compact crossovers, pairing a rugged ladder frame with a part-time four-wheel-drive system and low range. Our focus here is the four-cylinder 4×4 configuration sold during these two model years with either a 5-speed manual or 4-speed automatic. Shoppers choose it for durability, serviceability, and lower running costs versus V6 models, accepting modest straight-line pace. This guide explains what this specific variant is like to own and maintain today: how it’s built, the numbers that matter, common issues and fixes, practical service intervals, real-world driving behavior, and what to inspect before purchase. If you want a dependable daily that also handles trails, forest roads, snow, and light overlanding—without the complexity or thirst of bigger engines—the RZN185 4WD deserves a careful look.
Quick Overview
- Proven, timing-chain 3RZ-FE four-cylinder; straightforward access and long life with regular 5W-30 oil service.
- True part-time 4WD with low range; optional locking rear differential on select builds; excellent trail manners.
- Simpler and lighter than V6 4×4; slightly better front-end wear and easier cooling system service.
- Caveat: modest highway passing power; expect more downshifts and plan merges at elevation or with roof loads.
- Typical interval: engine oil and filter every 5,000 mi (8,000 km) or 6 months; brake fluid every 2 years.
What’s inside
- Detailed Overview — 4Runner 4WD (1999–2000)
- Specifications and Technical Data — RZN185 3RZ-FE
- Trims and Options, Safety and Driver Assistance
- Reliability, Common Issues and Service Actions
- Maintenance and Buyer’s Guide
- Driving and Performance
- How 4Runner Compares to Rivals
Detailed Overview — 4Runner 4WD (1999–2000)
The facelifted third-gen 4Runner polished a proven formula. The RZN185 pairs a longitudinal 2.7-liter inline-four with a part-time 4WD transfer case (high/low) and a front differential that engages only when selected, keeping wear and fuel consumption in check during 2H driving. Many trucks use Toyota’s vacuum-actuated front-axle disconnect; hoses and solenoids should be inspected on older examples. Rear axles are typically open; select years/trims offered a factory electronic rear differential lock, a worthwhile upgrade for rough terrain.
Chassis engineering is classic Toyota truck: a boxed ladder frame for durability, double-wishbone front suspension with coilovers, and a four-link solid rear axle with coils. Hydraulic rack-and-pinion steering (unusual among body-on-frame SUVs of the era) provides a tidy on-center feel and predictable response. Brakes are front ventilated discs and rear drums; ABS availability depends on trim and build. The cabin seats five with foldable rear benches and the signature roll-down tailgate glass that makes long cargo and in-cabin airflow simpler than most rivals.
The 3RZ-FE engine emphasizes reliability over spectacle. It uses chain-driven dual overhead cams, shim-over-bucket lifters that hold clearances for many miles, and multi-point EFI. Rated at 150 hp (110 kW) and about 240 Nm (177 lb-ft), it moves the 4Runner confidently at city speeds and on graded trails. Highway passing demands planning—especially with roof racks, all-terrain tires, or elevation—so drivers learn to keep the tachometer in the engine’s midrange for brisker response. Owners who favor simplicity, easy access, and long-term parts availability gravitate to this drivetrain; regular preventive maintenance beats performance add-ons in value per dollar.
Compared to the period V6 4Runner, the four-cylinder 4WD is a little lighter over the nose and often cheaper to own: no scheduled timing belt service, less heat to manage, and modestly lower insurance and fuel costs. The trade-offs are familiar to truck owners: slightly longer braking distances than modern disc-all-around SUVs, some wind sensitivity at freeway speeds, and drivetrain noises that reflect robust hardware rather than luxury isolation. Those are features, not flaws, for buyers seeking mechanical honesty and trail-friendly gearing.
Specifications and Technical Data — RZN185 3RZ-FE
Engine and Performance (gasoline, naturally aspirated)
| Item | Value |
|---|---|
| Code & layout | 3RZ-FE inline-4, DOHC, 16-valve, timing chain |
| Displacement | 2.7 L (2,693 cc) |
| Compression ratio | ~9.5:1 |
| Induction & fueling | Naturally aspirated; multi-point EFI |
| Rated power | 150 hp (110 kW) @ ~4,800 rpm |
| Rated torque | 240 Nm (177 lb-ft) @ ~4,000 rpm |
| Emissions/diagnostics | OBD-II |
| Fuel requirement | Regular unleaded |
| Fuel tank (usable) | ~70 L (18.5 gal) |
| Highway at 120 km/h (75 mph) | Often near EPA combined when stock; lifts/AT tires reduce economy 5–20% |
| Aerodynamics (context) | Cd mid-0.4s; frontal area ~2.7–2.8 m² |
Transmission and Driveline (4×4)
| Item | Value |
|---|---|
| Transmissions | 5-speed manual (R150F); 4-speed automatic (A340F) |
| Transfer case | Part-time 4WD; 2H / 4H / 4L; low range ~2.57:1 |
| Front axle engagement | Vacuum-actuated disconnect (many builds); inspect hoses/solenoids |
| Rear differential | Open; factory electronic locker available on select trucks |
| Final drives (typical) | ~4.10–4.56, build-dependent |
| Crawl character | With manual + low range, excellent throttle modulation and control |
Chassis and Dimensions
| Item | Value |
|---|---|
| Frame | Boxed ladder frame |
| Front suspension | Double-wishbone with coilover, stabilizer bar |
| Rear suspension | Four-link solid axle with coils, stabilizer bar |
| Steering | Hydraulic rack-and-pinion |
| Brakes | Front ventilated discs; rear drums; ABS availability by trim |
| Wheels/tires (factory) | 15–16 in; common sizes 225/75R15 to 265/70R16 |
| Wheelbase | 2,675 mm (105.3 in) |
| Length | ≈ 4,653–4,656 mm (183.2–183.3 in) |
| Width (body) | ≈ 1,690–1,730 mm (66.5–68.1 in) |
| Height | ≈ 1,715–1,740 mm (67.5–68.5 in) |
| Ground clearance | ≈ 230–260 mm (9.1–10.2 in) depending on tire/suspension |
| Curb weight (4×4 I-4) | ≈ 1,700–1,760 kg (3,750–3,880 lb) |
| GVWR | ≈ 2,380 kg (≈5,250 lb) |
| Turning circle | ≈ 11.6–11.9 m (38–39 ft) |
| Cargo volume (up/down) | ≈ 1,260 L / 2,260 L (≈45 / 80 cu ft) |
Fluids and Capacities (service planning)
| System | Specification & Capacity (typical) |
|---|---|
| Engine oil | 5W-30, ~4.8–5.5 L (5.1–5.8 qt) with filter |
| Coolant | Toyota Long-Life (red) / Super Long Life (pink), total ~7–9 L |
| Manual transmission (R150F) | 75W-90 GL-4/GL-5, ~2.3–2.6 L |
| Automatic (A340F) | Toyota Type T-IV / Dexron III, drain/fill ~2.0–3.5 L; overhaul ~7–9 L |
| Transfer case | 75W-90 GL-4/GL-5, ~1.2–1.5 L |
| Front differential | 75W-90 GL-5, ~1.1–1.3 L |
| Rear differential | 75W-90 GL-5, ~2.5–3.0 L (locker may require friction modifier per label) |
| Brake fluid | DOT 3/4; flush every 2 years |
| Power steering | ATF Dexron II/III (per cap) |
Selected torque values (commonly used):
- Wheel lug nuts — 113 Nm (83 lb-ft)
- Front caliper brackets — ~122 Nm (90 lb-ft)
- Differential drain/fill — ~49–59 Nm (36–44 lb-ft)
- Engine oil drain plug — ~39 Nm (29 lb-ft)
- Spark plugs — 18–22 Nm (13–16 lb-ft) (aluminum head; follow plug maker guidance)
Performance and Economy (4×4 3RZ-FE)
| Metric | 5-MT 4×4 | 4-AT 4×4 |
|---|---|---|
| 0–60 mph (typical ranges) | ~11.8–12.8 s | ~12.0–13.0 s |
| Top speed (indicated) | ~95–100 mph | ~95–100 mph |
| EPA mpg (city/hwy/comb) | 15 / 19 / 17 | 16 / 19 / 17 |
| Comb L/100 km (approx.) | ~13.8 | ~13.8 |
| Tow rating (braked)* | Up to 2,268 kg (5,000 lb) when properly equipped | |
| Payload (typical) | ~400–550 kg (880–1,210 lb) | |
| Roof load (dynamic) | ~75–100 kg (165–220 lb), rack dependent |
*Plan conservative speeds and increased following distances; an auxiliary trans cooler is wise on automatics used for towing.
Trims and Options, Safety and Driver Assistance
Trim landscape (1999–2000, four-cyl 4×4 emphasis):
- Base: Cloth seats, manual HVAC, steel wheels (often 15-inch), part-time 4WD with low range, power tailgate glass; ABS availability varies.
- SR5: The sweet spot for most 3RZ-FE 4×4 buyers. Adds alloy wheels, power accessories, roof rack, upgraded upholstery, and—depending on package—16-inch tires and appearance items.
- Limited: Typically paired with the V6 and more luxury features; a four-cyl 4×4 Limited is uncommon. If found, check equipment carefully—wheel/brake differences affect parts selection.
Option packages and mechanical tells:
- Rear differential lock (factory e-locker): Look for the dash switch; decode the axle code on the door jamb sticker to confirm.
- Gear ratios: Shorter ratios (~4.56) often accompany certain four-cyl configurations—good for trails and larger-than-stock tires.
- Wheel/rotor pairings: Some 16-inch packages use different rotors; confirm before ordering brake parts.
- ABS: If equipped, bleeding procedures and diagnostics differ from non-ABS; a fluid flush can markedly improve pedal feel.
Safety ratings (era-correct context):
- In period tests, this generation achieved Acceptable in the IIHS moderate-overlap frontal evaluation. NHTSA testing of the era used different protocols than today, including rollover assessments that tended to flag tall body-on-frame SUVs as higher risk relative to modern crossovers.
Safety systems and child seats:
- Dual front airbags, pretensioners, and an energy-absorbing column were standard by this facelift. These models predate LATCH; child-seat installation uses belts and approved locking methods per the owner’s manual. No modern crash-avoidance features (AEB, ACC, lane support) were offered, so tire choice, brake maintenance, and driver attention carry added importance.
Year-to-year notes (1999 vs 2000):
- Styling, interior trim, and equipment bundling were refined through minor package changes. Focus your inspection on build-specific items: ABS presence, axle code, wheels/rotors, and locker option.
Reliability, Common Issues and Service Actions
Overall verdict: The 3RZ-FE/part-time 4WD drivetrain is one of the most durable combinations of its era. Age, climate, maintenance quality, and modifications now dominate the fault pattern more than design weaknesses. Below is a practical map by prevalence and cost impact.
Common (frequent; low-to-medium cost)
- Lower ball joints (LBJs):
Symptoms: wander, toe change over bumps, front-end clunk.
Cause: wear from age/contamination; heavy tires accelerate it.
Fix: replace with quality LBJs; torque at ride height; align afterward. - Frame and underbody corrosion (salt-belt):
Symptoms: scaling on rear rails, body mounts, hitch points, tank straps.
Fix: internal inspection with borescope, remove scale, treat and coat; welded sections where advanced. - Rear axle seals contaminating drums:
Symptoms: oily backing plates, reduced rear brake bite.
Fix: seals/bearings as needed; clean/replace shoes and hardware; clear axle breather. - Cooling system age-outs:
Symptoms: radiator end-tank cracks, soft hoses, weak heater.
Fix: new radiator/thermostat/hoses; correct Toyota coolant; proper bleed.
Occasional (medium prevalence; medium cost)
- Valve cover and plug-tube seals:
Symptoms: oil smell, oil in plug wells, coil boot swelling.
Fix: valve cover gasket set; PCV valve/hose refresh. - Accessory belt and idler bearings:
Symptoms: cold squeal or bearing growl.
Fix: replace belts and noisy idlers; confirm pulley alignment. - A340F automatic shift quality (hot):
Symptoms: 2–3 flare, lazy lock-up, occasional shudder.
Fix: staged drain/fills with T-IV/Dex III (per dipstick cap); verify throttle cable (if equipped) and consider valve body service if persistent. - Manual shifter seat/bushing wear (R150F):
Symptoms: vague gates, excessive play.
Fix: inexpensive seat/bushing kit; quick DIY. - 4WD ADD (automatic disconnecting differential) vacuum issues:
Symptoms: delayed 4H engagement, lights flashing, or no engagement.
Fix: inspect/replace cracked vacuum lines, test solenoids, verify front-axle actuator movement.
Rare (low prevalence; high impact)
- Head gasket failure (3RZ-FE): uncommon, typically after severe overheating.
- ABS actuator leaks/failures: expensive; verify before parts-cannon decisions.
- ECU faults: rare; more often grounds/connectors corrode—clean and re-secure.
Driveline and chassis notes:
- U-joints and slip yokes: grease serviceable joints on schedule; address driveline clunk with lubrication and inspection.
- Transfer case and diff seals: age-related seepage—watch for drops on the driveway after long sits.
- Shock/suspension bushings: polyurethane increases precision but can add NVH; quality rubber keeps OE ride.
Recalls, TSBs, and extended coverage:
- No widespread engine or frame recalls specific to this four-cyl/4×4 subset are typical, but always run an official VIN recall check and retain dealer printouts. Aftermarket accessories (lighting, tow hitches) may have recall histories—verify part brands and dates.
Pre-purchase documents to request:
- Oil/coolant/brake fluid intervals, differential and transfer case services, and any front-end rebuild work (LBJs, tie-rods, bushings). For automatics, ask for ATF service mileage and method (drain/fill vs flush).
Maintenance and Buyer’s Guide
Practical maintenance schedule (normal use; shorten for heavy towing, frequent short trips, dust, or extreme temps):
- Engine oil & filter: 5,000 mi (8,000 km) or 6 months; 5W-30.
- Engine air filter: Inspect 12 months / 15,000 mi (24,000 km); replace on condition.
- Cabin filtration: Many trucks shipped without a cabin filter; retrofit kits exist—inspect HVAC box annually.
- Spark plugs: Conventional copper ~30,000 mi (48,000 km); verify gap/torque; follow part-number guidance if using long-life plugs.
- Fuel filter (external): 60,000–90,000 mi (96,000–145,000 km); inspect lines for corrosion.
- Coolant: Red Long-Life 2–3 years / 30,000–50,000 mi; Pink Super Long Life 5–7 years / 100,000–150,000 mi—do not mix types.
- Drive belts & hoses: Inspect each oil change; replace 60,000–90,000 mi or on condition.
- A340F ATF: Drain/fill 30,000–60,000 mi; avoid power flushes on high-milers—use staged services.
- R150F manual oil: 30,000–60,000 mi if water crossings/dust; otherwise ~60,000+ mi.
- Transfer case & differentials: 30,000–60,000 mi depending on use; confirm breathers are free.
- Brake fluid: Flush every 2 years; service front caliper slide pins; adjust rear drums.
- Brake pads/shoes/rotors/drums: Inspect each rotation; replace to spec; renew drum hardware as needed.
- Tire rotation & alignment: Rotate 5,000–7,500 mi; align annually or after front-end work.
- Valve clearances: Shim-over-bucket is stable; inspect ~100,000 mi or if noise/misfire suggests.
- 12 V battery: Load-test annually after year 3; typical life 4–6 years.
Fluid specs & capacities (quick recap):
- Engine oil: 5W-30; ~5.1–5.8 qt with filter.
- Manual/auto/transfer/diffs: 75W-90 GL-4/GL-5 (boxes/diffs/transfer as specified); Type T-IV/Dex III for A340F.
- Coolant: Toyota LL/SLLC; Brake: DOT 3/4; PS: Dexron II/III.
Essential torque references:
- Lug nuts 113 Nm (83 lb-ft); oil drain ~39 Nm (29 lb-ft); diff plugs ~49–59 Nm (36–44 lb-ft); spark plugs 18–22 Nm (13–16 lb-ft).
Buyer’s inspection checklist (4×4 emphasis):
- Frame & rails: Probe rear kick-ups, body mounts, tank straps; borescope inside boxed sections for hidden perforation.
- Front end: LBJs, inner/outer tie-rods, control-arm bushings, front wheel bearings; steering on-center feel during test drive.
- 4WD system: On loose surface, verify 4H/4L engagement; listen for front-axle actuator; check ADD vacuum lines and transfer-case lever/linkage.
- Axles & brakes: Look for axle-seal seep; confirm parking brake holds on a slope; check rear drum condition.
- Transmission:
- Automatic: From a hot start, ensure clean 1–2 and 2–3 shifts and torque-converter lock-up; no flare/shudder.
- Manual: Smooth clutch take-up, no synchro crunch, no shifter buzz.
- Cooling system: Radiator end-tanks, thermostat housing, heater performance; no sweet coolant odor in cabin.
- Electrical: Rear window operation, alternator output under load, ground straps clean/tight.
- Body & seals: Windshield surround, roof rack mounts, tailgate garnish; door drains open.
- Tires/wheels: Avoid oversized mud-terrains on stock gearing—stress on LBJs/brakes and sapped performance.
What to seek/avoid:
- Seek: Stock or lightly modified SR5 4×4 with documented fluid services, refreshed front end, clean frame, and working 4WD. A factory rear locker is a plus for off-roaders.
- Be cautious of: Lifted rigs on heavy tires without matching gearing, undercoating that hides frame patches, neglected ATF on automatics, chronic overheating histories.
- Durability outlook: With corrosion managed and fluids on time, the 3RZ-FE/4×4 combination commonly exceeds 300,000+ miles (480,000+ km) on the original long block.
Driving and Performance
Ride and handling: The 4Runner’s ladder frame and coil-spring layout yield a compliant ride on broken pavement and washboard. With healthy shocks and bushings, body control is tidy and secondary motions are well-damped. Steering is moderate-weight with predictable on-center; worn LBJs or alignment drift are the usual culprits when trucks feel vague. Compared with V6 versions, the four-cyl 4×4 feels marginally lighter at the nose, aiding turn-in and reducing understeer at casual speeds.
NVH: At idle and cruise, the 3RZ-FE is smooth for a truck four; above ~4,000 rpm it sounds busy but honest. Tire selection sets cabin hum more than the engine does. Roof baskets and light bars add wind noise; if you value highway quiet, choose mild all-terrain tread and keep accessories streamlined.
Powertrain character:
- 5-speed manual (R150F): Best for response, grade control, and technical trail work. Shorter gearing with low range provides confident crawling without throttle surge.
- 4-speed automatic (A340F): Durable and smooth; kicks down decisively with a firm throttle push but will hunt on rolling grades if over-geared tires are fitted. Regular drain/fills improve feel; an auxiliary cooler is cheap insurance for towing or desert heat.
Real-world efficiency: Stock trucks typically return 16–18 mpg (US) mixed (13–15 L/100 km). At 120 km/h (75 mph), many see figures near EPA combined; add a roof rack, lift, or aggressive A/T tires and expect a 5–20% penalty. Short winter trips and ethanol blends further reduce mpg.
Braking: Disc-drum hardware means a bit more pedal travel than modern setups. Proper rear drum adjustment, fresh fluid, and lubricated front slide pins restore confidence. Higher-friction pads and stainless lines help for mountain driving but won’t magically shorten distances—tire compound still dominates.
Traction and control: The part-time 4WD system is straightforward: 2H for dry pavement, 4H for loose or slippery surfaces, 4L for steep climbs/descents or technical obstacles. Trucks with the rear locker walk up surprisingly difficult climbs on stock suspension. Tire quality and pressures are the biggest levers for off-road performance; a mild lift, skid plates, and recovery points are smart, reliability-friendly upgrades.
Load and towing: Properly equipped, tow up to 5,000 lb (2,268 kg), but comfort lives in the 1,500–3,000 lb (680–1,360 kg) range. Expect 25–40% worse fuel economy when towing or running fully loaded, longer stopping distances, and higher transmission temperatures (again: consider a cooler on automatics).
How 4Runner Compares to Rivals
Jeep Cherokee XJ 4×4 (4.0L I-6): Quicker in a straight line with a huge aftermarket. The unibody can fatigue at high miles with hard use; cooling systems need diligent care. The 4Runner’s ladder frame, timing-chain four-cyl, and rack-and-pinion steering often age more gracefully. For slow technical trails, a factory rear locker levels the field.
Nissan Pathfinder R50 4×4 (3.3L V6): More car-like ride from its unibody and a cabin that can feel quieter on freeway commutes. The timing belt adds periodic cost; parts availability is good but the 4Runner’s ecosystem is broader. Off-road, the 4Runner’s low range and aftermarket support usually win.
Ford Explorer 4×4 (’99–’01, OHV/SOHC V6): Abundant and budget-friendly to buy used, but the SOHC timing chain layout can be a service risk. The 4Runner tends to hold value better; steering feel and durability of front-end components age favorably on the Toyota with proper maintenance.
Bottom line: If you prioritize longevity, straightforward service, and true 4×4 hardware, the 3RZ-FE 4Runner remains a benchmark. If fast highway passes or frequent heavy towing are essential, consider a V6 alternative—or keep expectations realistic and gearing/tire choices conservative.
References
- Gas Mileage of 1999 Toyota 4Runner 2025 (EPA/DOE Database)
- 1999 Toyota 4Runner 2025 (Safety Rating)
- Scheduled Maintenance Guide 1999 (Owner’s Manual Supplement)
- Look up Safety Recalls & Service Campaigns by VIN 2025 (Recall Database)
Disclaimer
This article is for informational purposes and isn’t a substitute for professional diagnosis or repair. Specifications, torque values, intervals, and procedures can vary by VIN, market, options, and build date. Always verify numbers and procedures in your official Toyota service documentation and under-hood labels. If this guide helped, please consider sharing it with fellow enthusiasts on Facebook or X/Twitter to support xcar’s work.