The 2020 Infiniti QX80's 7-speed automatic transmission handles the substantial power of the 5.6L V8 while also managing towing duties up to 8,500 pounds. When this transmission begins slipping—engine revving without corresponding acceleration—the heavyweight's drivetrain needs attention.
Understanding Transmission Slip
Slipping occurs when the transmission's clutches or bands can't maintain full grip under power. Instead of transferring all engine torque to the wheels, some is lost as the clutches spin against each other rather than locking firmly.
Symptoms of Slipping
- Engine RPM rises but vehicle hesitates before accelerating
- Delayed engagement when shifting from Park to Drive
- RPM flare during gear changes—revs spike between gears
- Loss of power while climbing hills or towing
- Transmission warning light or messages
- Burnt smell from transmission fluid
Common Causes
Low or Degraded Fluid
Transmission fluid serves multiple functions: lubrication, cooling, and providing the friction properties for clutch engagement. Low levels or degraded fluid can cause slipping.
Worn Clutch Packs
The clutch friction material wears over time. Heavy towing or spirited driving accelerates wear. Once material is gone, clutches slip under load.
Faulty Solenoids
Electronic solenoids control hydraulic pressure to clutch packs. Failed solenoids can result in insufficient pressure, causing slip.
Valve Body Issues
The valve body directs hydraulic pressure throughout the transmission. Worn passages or stuck valves affect clutch engagement pressure.
Torque Converter Problems
The torque converter's lockup clutch can slip independently, creating symptoms similar to transmission slip.
Repair Costs
| Repair | Parts | Labor | Total |
|---|---|---|---|
| Fluid service | $150-$300 | $150-$250 | $300-$550 |
| Solenoid replacement | $200-$500 | $400-$700 | $600-$1,200 |
| Valve body replacement | $600-$1,000 | $500-$800 | $1,100-$1,800 |
| Transmission rebuild | $2,000-$3,500 | $2,000-$3,500 | $4,000-$7,000 |
| Transmission replacement | $4,000-$6,000 | $2,000-$3,500 | $6,000-$9,500 |
Before Major Repairs
Start with fluid level and condition check. Many slip complaints, especially intermittent issues, respond to fluid service. Confirm internal damage before committing to major rebuild.