TECHNICAL SERVICE BULLETIN: TRANSMISSION FLUID APPLICATION GUIDE - This bulletin has been revised to include additional information. New/revised sections of this bulletin are indicated by a black bar in the margin area. This bulletin provides information relating to the correct transmission fluid type and fill quantity requirement for each Kia model. A flush is required ONLY when a transmission is replaced, and the transmission oil cooler is transferred to the new transmission.
full bulletin at NHTSA ↗2018 Kia Sportage powertrain problems
moderate 15 complaints filed with NHTSA · avg repair $2,500 · see powertrain across all vehicles →
Complaints
15
Recalls
0
Avg fix
$2,500
When does it fail?
Of the 15 powertrain complaints filed for the 2018 Kia Sportage, here's the actual mileage breakdown — failures cluster heaviest at 25,000-50,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
No new NHTSA powertrain complaint has been filed on this vehicle in over 4 years — the issue may be aging out of the active population.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering powertrain on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
This bulletin provides information relating to the correct transmission fluid type and fill quantity requirement for each Kia model. A flush is required ONLY when a transmission is replaced.
full bulletin at NHTSA ↗PITSTOP: AWD SYSTEM CONCERN DUE TO TIRE CIRCUMFERENCE - This Pitstop provides information regarding potential concerns with the All-Wheel-Drive (AWD) system due to tire sizes of differing circumference. Some customers may complain of a chatter sensation felt in the drivetrain of the vehicle and/or the failure of drivetrain component(s). A difference in tire size (width, aspect ratio, construction, rim diameter etc.) may be the cause.
full bulletin at NHTSA ↗TECHNICAL SERVICE BULLETIN: TRANSMISSION FLUID APPLICATION GUIDE - This bulletin provides information relating to the correct transmission fluid type and fill quantity requirement for each Kia model. A flush is required ONLY when a transmission is replaced, refer to applicable vehicles in the chart starting on page 2.
full bulletin at NHTSA ↗TECHNICAL SERVICE BULLETIN - PARTIAL REPAIR OF 4WD COUPLING - This bulletin provides the procedure information regarding the partial repair of the Four Wheel Drive (4WD) Coupling Assembly, Pressure Sensor, Actuator Motor or 4WD harness on some 2011-2020 Sportage (SL, QL) and 2013-2020MY Sorento (XMa, UMa) 4WD vehicles for a concern regarding: ï· Oil leakage from the 4WD coupling assembly ï· 4WD Malfunction and MIL lamp ON with DTCs ï· Abnormal noise or vibration while driving
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
Owners of 2018 Kia Sportages report a spectrum of powertrain failures that create genuine safety hazards. Engine knock appears early in ownership and can escalate to catastrophic failure; one owner faced a $10,000 replacement when the engine seized from low oil after warning lights appeared simultaneously. A related fuel pump failure caused repeated fuse blowouts (12 in three months), battery drain that killed multiple batteries, and roadside stalling—yet the fuel pump replacement failed within 50 miles of warranty expiration.
Transmission problems dominate the complaints. Owners describe the transmission intermittently slipping out of gear at 30–40 MPH and highway speeds, causing RPM surges while the vehicle coasts powerless, creating acute collision risk during merges. Some cars slip into neutral without warning, losing all response to throttle input. Others downshift violently into first gear and jerk harshly before re-engaging. A transmission failure was documented at 64,456 miles.
Loss of motive power and stalling occur with little warning—no check engine light in many cases. One owner's vehicle shook violently on startup and lost speed rapidly while overheating. Poor acceleration response is chronic; owners report the car barely moves when hard acceleration is attempted, especially uphill, with fuel economy dropping to 11 MPG. Dealerships consistently fail to diagnose these issues during test drives and offer no remedy without reproducibility in their shop.
Same Kia Sportage powertrain reports on nearby years: 2017
Failure modes owners describe
Engine Knock and Failure
Owners report engine knock that leads to catastrophic engine failure. One owner experienced an oil light and multiple warning lights, requiring a complete engine replacement. Another reported persistent engine knock followed by complete engine failure at 64,456 miles. A third noted the knock occurred immediately after purchase and remained unresolved despite multiple dealership visits.
When: Reported around 44,000 miles in one case; another at 64,456 miles; one owner with unknown mileage but immediately after purchase
Symptoms owners cite: Knocking noise from engine bay; Oil light illumination followed by battery and check engine lights; Vehicle deceleration and loss of power; Engine overheat issues
Codes mentioned: P0101 or related fuel system codes (implied by fuel pump failure diagnostics)
Repairs/costs cited: One owner faced $10,000 engine replacement cost; another required fuel pump and injection pump replacement in September 2020
Recalls/TSBs owners mention: Recall mentioned in narrative #1 (specific recall number redacted); narrative #2 states owners were told a recall existed but was supposedly already fixed
Transmission Slipping and Loss of Power
Transmission intermittently slips out of gear or loses engagement, causing the vehicle to coast without power response despite engine revving. Occurs at highway speeds and during acceleration, creating hazardous merge conditions. Symptoms include RPM surging while speed remains unchanged, and no warning lights. Dealers cannot replicate the issue and offer no remedy.
When: Immediately after purchase while under warranty in one case; occurs intermittently throughout ownership
Symptoms owners cite: Transmission slips out of gear at 30-40 MPH; RPM revs while speed doesn't change; Loss of power during acceleration and merging; No warning lights or messages; Engine revs but transmission doesn't respond; Vehicle coasts without motive power for several seconds
Repairs/costs cited: No repairs completed; dealer stated inability to diagnose without reproducibility
Recalls/TSBs owners mention: No recall or service bulletin issued per owner reports; Kia escalation department contacted but offered no resolution
Transmission Downshift and Jerking
Transmission unexpectedly downshifts into first gear causing vehicle to jerk violently and briefly lose motive power before slamming back into gear. Owners also report abnormal RPM fluctuation while driving uphill or downhill, and burning odor from under hood.
When: Unknown mileage in one report; occurred during hill driving
Symptoms owners cite: Unexpected downshift to first gear; Vehicle jerking and loss of motive power; Slamming back into gear; RPM fluctuation on grades; Abnormal engine revving; Burning odor from engine bay entering cabin via A/C
Repairs/costs cited: Independent mechanic replaced thermostat and driver's side window electric switch but failed to resolve transmission issue
Transmission Slipping to Neutral
Transmission unexpectedly slips into neutral during driving at highway and low speeds, causing RPM to surge while the vehicle loses motive power. Occurs when accelerating and during turning, presenting serious collision risk. No warning lights illuminate before or during the event.
When: One case at 37,000 miles; others at undisclosed mileage
Symptoms owners cite: RPM surges suddenly while car appears in neutral; Loss of motive power during acceleration; Occurs during turns at low speed and highway driving; RPM goes very high then drops and car returns to drive; No acceleration response when pressing gas pedal; No warning lights
Repairs/costs cited: No repairs completed; dealers could not duplicate the failure
Recalls/TSBs owners mention: Manufacturer notified in at least one case; local dealers aware but unable or unwilling to diagnose
Fuel Pump Failure with Electrical Drain
Fuel pump shorts out causing repeated fuse failures (12 fuses over 3 months) and complete battery drain that has killed multiple batteries. Vehicle dies on the road and refuses to start. After fuel pump replacement in September 2020, symptoms returned within 50 miles of warranty expiration, leaving owner stranded.
When: Started at 44,000 miles; replacement attempted at around 50,000 miles; recurred immediately after
Symptoms owners cite: Repeated fuse failures (12 in 3 months); Battery drain killing multiple batteries; Vehicle dies at stops and during highway driving; Loss of fuel pressure; Engine won't start; No fuel delivery after restart
Repairs/costs cited: Fuel pump and injection pump replaced in September 2020; issue recurred within 50 miles and 1 day of warranty expiration; fuel pump diagnosed as shorting out and causing fuse failure
Loss of Motive Power and Stalling
Vehicle stalls unexpectedly during driving and loses ability to accelerate, with power capped at 20 MPH or less. Check engine light illuminates. One owner also reported the vehicle shaking violently on startup with rapid speed decrease and overheating.
When: One case at 46,300 miles; others at undisclosed mileage
Symptoms owners cite: Vehicle stalls during driving; Unable to accelerate above 20 MPH; Check engine light illumination; Loss of motive power; Violent shaking on startup; Rapid speed decrease; Overheating; Loss of power going uphill
Codes mentioned: Check engine light
Repairs/costs cited: One owner required unknown engine repairs and was told driveshaft replacement needed but warranty had expired; another owner told powertrain control module needs reprogramming
Recalls/TSBs owners mention: Manufacturer notified in at least one case
Poor Acceleration Response
Vehicle fails to accelerate in a timely manner when starting from a stop or at low speeds. Occurs intermittently. When attempting hard acceleration, vehicle barely moves and loses speed, especially going uphill. Fuel economy drops to 11 MPG.
When: Intermittent throughout ownership; one case at 64,456 miles
Symptoms owners cite: Delayed acceleration response from stops; Minimal power when pressing gas pedal hard; Loss of speed and power on hills; Severely reduced fuel economy (11 MPG reported); Engine rev but speed doesn't change
Codes mentioned: P0101 or related powertrain control codes (implied)
Repairs/costs cited: One owner told powertrain control module needs reprogramming
Transmission Not Shifting Correctly
Transmission fails to shift smoothly or at all, with improper shift points and jerky engagement. One owner reported transmission failure at 64,456 miles with the shop discovering complete transmission failure occurring rapidly.
When: At 64,456 miles in one documented case
Symptoms owners cite: Not shifting correctly; Improper shift points; Jerky transmission engagement; Complete transmission failure
Repairs/costs cited: Shop diagnosed complete transmission failure requiring replacement
Synthesized from 15 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 2 most recent
Intermittently, the car’s transmission slips out of gear completely, around 30-40 MPH. It gets back into gear after a few seconds. At times, it has presented a safety risk especially when attempting to merge on a highway in a short merge lane. When the slipping occurs in this situation, the car no longer accelerates and merging into traffic becomes very problematic and increases the risk of a…
I bought this car in may of 2020 with 44k on the odometer. Three days later I was on a 3400 mile road trip on the highway when I started hearing knocking from the engine bay. I took it in and had them listen. They told me it was completely normal. The knock went away for about 400 miles then came back. I took it in to 4 different dealerships. I got told there had been a recall on the motor but…
Had powertrain trouble with your 2018 Kia Sportage?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the powertrain problem on the 2018 Kia Sportage?
It's a documented issue but not catastrophic. 15 complaints have been filed. Repairs average $2,500 and most owners catch it before it causes a breakdown.
At what mileage does the powertrain typically fail?
Based on the 15 complaints filed, powertrain issues most often appear around 40,575 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $2,500 for powertrain repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to powertrain?
No active recalls currently cover powertrain issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2018/Kia/Sportage.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.