1999 Acura SLX Problems: 2 Issues Every Owner Should Know
1999 model year · NHTSA recalls, manufacturer TSBs, and owner forum reports · Updated May 2026
According to Au7o's research across NHTSA recalls, manufacturer TSBs, and owner forum reports, the 1999 Acura SLX has 2 documented known issues. No issues are rated critical, indicating generally reliable ownership. Across all issues, repair costs range from $300 to $2,000. DIY maintenance guides at au7o.io.
All 2 Known Issues
On the 1996-1999 Acura SLX, in August 1996 Consumer Reports published rollover test results showing the 1996 Acura SLX (a rebadged Isuzu Trooper) tipped onto two wheels during avoidance-maneuver testing at low speeds. Consumer Reports issued the rare 'Not Acceptable' rating and publicly demanded Isuzu and Acura halt sales and recall the vehicles. The story was front-page news and devastated SLX/Trooper resale value for the rest of the production run. Acura/Isuzu pushed back, and NHTSA reviewed the issue but declined to find a defect — no recall was ever issued. The SLX continued to sell through 1999. Despite the no-defect ruling, the rating affects buyers searching for 'is the SLX safe' or 'Acura SLX problems' even today. Used buyers should know the body-on-frame chassis IS taller and narrower than typical Acuras, and rollover characteristic differs from car-based SUVs. The fundamental physics are unchanged from a 1996 Trooper.
Common Symptoms
- Vehicle leans noticeably in normal-speed cornering
- Tendency to skip/hop in tight low-speed turns with rear axle
- Two-wheel tip during emergency avoidance maneuvers (the original CR finding)
- Wandering or instability in crosswinds at highway speeds
How to Fix
There is no mechanical fix because there's no mechanical defect — the Consumer Reports finding was a stability characteristic, not a failed part. Buyers and owners should: (1) know the vehicle's center of gravity is high; avoid emergency lane-change maneuvers above 35 mph if possible. (2) Keep the suspension and tires in spec — worn shocks and underinflated tires make rollover more likely on any tall SUV. (3) Use the OEM-spec tire size; oversized off-road tires raise the center of gravity further. (4) Modern stability control didn't exist on the SLX — drive accordingly. Used-buyer tip: the SLX/Trooper market is depressed permanently because of this story, which makes well-maintained examples a relative bargain — but go in eyes-open about the handling envelope.
What Owners Are Using
Parts and tips from 0+ owners who fixed this issue
- TipIf you're buying used, know that NHTSA reviewed and declined to find a defect — but the body-on-frame chassis is genuinely tall and narrow. Drive accordingly: no emergency lane changes above 35 mph, keep tires at spec, keep shocks fresh.
- NoteDon't fit oversized off-road tires. The SLX is already at the edge of stable proportions; lifting it or adding 33+ inch tires makes the original CR finding more accurate, not less.
- TipUsed-buyer angle: the rollover story permanently depressed SLX/Trooper market values. A well-maintained one is genuinely cheap for what it is — but go in knowing the handling envelope and avoid spirited driving.
On the 1996-1999 Acura SLX, the SLX is a rebadged Isuzu Trooper, and inherits the same drivetrain failures that plague the Trooper. The rear differential develops a high-pitched whine, primarily under load at highway speed, caused by ring-and-pinion wear from imperfect gear mesh. Once the whine starts it progressively worsens; if ignored, the gears can strip. Separately, the Borg-Warner transfer case used in 1998-1999 SLX/Trooper has documented seal-leak and bearing-wear failures. CRITICAL FLUID NOTE: do not assume any specific fluid spec without checking your service manual — early sources circulated incorrect fluid specifications for the Borg-Warner transfer cases used in these vehicles. Always verify the correct fluid by manufacturer documentation or a Borg-Warner technical lookup before topping off — using the wrong fluid is a known cause of accelerated failure.
Common Symptoms
- High-pitched whine from rear axle under load (50-65 mph cruise)
- Whine that changes pitch with throttle (worse on gas, quieter coasting)
- Transfer case howl or grinding in 4WD only
- Fluid leaking from transfer case seals
- Vibration through the floor at highway speed
- Burnt or metallic-smelling rear diff fluid on inspection
How to Fix
REAR DIFF: If whine is noticed early, change the gear oil to fresh 80W-90 GL-5 and run a friction modifier. This will not stop existing wear but can slow it. Once whine is pronounced, the only durable fix is a remanufactured rear axle assembly ($800-1,400) or a rebuild of the existing ring and pinion ($1,200-2,000 at a specialist). TRANSFER CASE: Verify the manufacturer-spec fluid is being used — DO NOT default to motor oil or ATF without confirming. Check fluid level every oil change. If the case is whining or has external leaks, source the correct Borg-Warner rebuild kit by part number from your vehicle's exact model year + transmission combination — multiple BW transfer case variants were used across SLX/Trooper years and the parts are NOT interchangeable.
What Owners Are Using
Parts and tips from 0+ owners who fixed this issue
- NoteThe BW4422 transfer case REQUIRES 5W-30 motor oil — NOT gear oil, NOT ATF. Wrong fluid is the #1 killer. Most quick-lube shops get this wrong. Check the owner's manual or service manual before allowing any shop to top it off.
- UpgradeBW4422 transfer case rebuild kit (BK4422) — covers seals, bearings, chain on the 1998-2002 SLX/Trooper/VehiCROSS transfer case. $300-500 in parts. (Transmission Parts Distributors #BK4422)
- TipCatch rear diff whine early — fresh GL-5 80W-90 with friction modifier won't reverse wear but can buy 10-20k miles of grace before a rebuild is mandatory.