This service bulletin provides information on some vehicles that may rock or move slightly forward or rearward while in Park at start up after cold soak. This condition may be accompanied by a clunk noise. This is a slight movement that is more often seen visually, rather than felt, when viewed from the outside and using the auto-start feature, if equipped.
full bulletin at NHTSA ↗2007 Chevrolet Trailblazer powertrain problems
moderate 14 complaints filed with NHTSA · avg repair $2,500 · see powertrain across all vehicles →
Failure mileage
Complaints
14
Recalls
0
Avg fix
$2,500
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.
GM is receiving damaged (cracked or broken) transmission cores returned to the reman facilities. The damage is being caused either in the removal process by the technician, or inadequate packaging or shipping. This bulletin advises the dealers to be more careful not to damage the transmissions during removal and to package the core properly for return.
full bulletin at NHTSA ↗This bulletin provides information on the harmful effects of water or ethylene glycol in transmission fluid.
full bulletin at NHTSA ↗This service bulletin provides technicians with information to help identify the differences between what is considered a fluid leak, and what is considered fluid seepage.
full bulletin at NHTSA ↗This Warranty Admin service bulletin provides guidelines for Dealers Not Required and for Dealers Required to Contact the PQC for engine or transmission assembly replacement and explains the PQC process, GWM Transaction submission, vehicle service record retention and proper handling of assembly returns for Canadian Dealers only.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
Fourteen complaints from 2007 Trailblazer owners describe powertrain failures spanning throttle control, transmission reliability, and component corrosion. The most consistent problem is transmission cooler line corrosion starting as early as 59,000 miles—lines rust through, leak fluid, cost $150–$500 to replace, and rust again within three years. GM acknowledges this in TSB PIT-4722 but won't cover repairs on 2007 models.
Power loss during acceleration is another recurring safety issue. One owner's vehicle dropped from 2000 RPM to 500–600 RPM mid-acceleration despite foot on the throttle; the dealer replaced the PCM, but the problem returned within two months. Another experienced complete transmission failure at an intersection.
Throttle hang—where engine RPM sticks around 2000 when downshifting—plagues multiple owners. One documented the issue with vehicle logs showing the engine overspeeding relative to the transmission input shaft. GM told him the vehicle is acting as designed, despite acknowledging other owners report the same problem.
Transmission failures range from catastrophic (no drive or reverse) to creeping quality issues after rebuild (hard shifts, hesitation, gas pedal sticking). Shift lever inadvertently moving from Drive to Neutral, bad front axles with binding gears, and the torque converter locking hard on hill climbs round out the cluster. Dealers struggled to diagnose intermittent faults, sometimes dismissing problems as driver error or customer responsibility.
Same Chevrolet Trailblazer powertrain reports on nearby years: 2005 · 2006 · 2008
Failure modes owners describe
Throttle hang and improper idle control
Engine RPM hangs around 2000 RPM after acceleration when driver needs to slow down, causing extended high-idle periods (up to 16 seconds reported) and difficulty decelerating. AC compressor engagement can worsen the issue. Owner documented the problem with logs showing engine speed raising above transmission input shaft speed, indicating a mechanical or electronic control malfunction.
When: During deceleration after acceleration; problem appears across different driving conditions
Symptoms owners cite: Throttle hangs at ~2000 RPM; Difficulty slowing down despite braking; Extended high-idle periods during deceleration; Engine RPM hunting around 1650 RPM ±75 RPM; AC clutch engagement correlates with worsening; Brake-required to slow from 2000 RPM hang-up
Repairs/costs cited: No successful fix documented; owner sued GM (settlement paid) but problem remained unresolved
Recalls/TSBs owners mention: GM stated the vehicle is acting as designed; GM Service Request # 71-661522934 filed under "HIGH IDLE"
Sudden power loss during acceleration
Vehicle loses power unexpectedly during acceleration, with RPM dropping from ~2000 to 500-600 RPM even with throttle applied. Problem recurs after dealer repair (PCM replacement). Diagnosed intermittently, making dealer diagnosis difficult. Safety risk noted when vehicle loses power during street crossing and turning scenarios.
When: During acceleration; first occurred in January 2010, recurred in March 2010 after PCM replacement
Symptoms owners cite: Sudden loss of power during acceleration; RPM drop from 2000 to 500-600 RPM while pressing gas pedal; Intermittent problem difficult to replicate; Problem reoccurs after PCM replacement
Repairs/costs cited: Powertrain Control Module replaced at dealership; repair failed to resolve issue
Recalls/TSBs owners mention: GM Case # 71-810026931; GM customer service initially refused to dispatch specialized technician without owner paying for second dealership visit and associated costs
Transmission cooler line corrosion and leakage
Transmission cooler lines corrode prematurely and leak transmission fluid. Problem occurs even on low-mileage vehicles (59,000 miles reported). Lines corrode again within 3 years of replacement. TSB exists covering 2000-2006 models, but coverage status unclear for 2007. Dealer initially blamed customer (blamed snow in muffler) during diagnosis delay of 19 months.
When: Variable mileage; one case at 59,000 miles; recurring within 3 years of replacement
Symptoms owners cite: Transmission fluid puddles under vehicle; Visible corrosion on transmission lines; Oil spots on driveway; Lines rust out again after replacement; Rapid degradation despite repair
Repairs/costs cited: Line replacement cost ~$500 per owner; another owner spent ~$150 for lines, fluid, and filter; problem recurs requiring repeated repairs
Recalls/TSBs owners mention: TSB #PIT-4722 exists for 2000-2006 light-duty trucks (covers transmission oil cooler line corrosion); GM acknowledged the defect is known but refused warranty repair, stating it is customer responsibility; no recall issued
Transmission failure and loss of drive/reverse
Transmission fails completely, leaving vehicle with no power in drive or reverse. One case failed after only 2 days of ownership with just 95 miles on the odometer (15 miles at purchase). After GM placed rebuilt transmission in the vehicle, residual problems persist including hesitation and gas pedal sticking.
When: Very early in vehicle ownership; one case at 80 miles, another at 80,000 miles
Symptoms owners cite: No power in reverse; No power in drive; Complete transmission failure; Post-rebuild hesitation during acceleration; Post-rebuild gas pedal sticking; Post-rebuild feeling of near-stall during acceleration
Repairs/costs cited: GM replaced/rebuilt transmission in warranty; residual drivability problems persist after repair; rebuilt unit exhibits hesitation and sticking pedal issues
Recalls/TSBs owners mention: GM offered transmission repair or replacement only; refused vehicle replacement or refund; no TSB or extended coverage noted
Inadvertent shift lever movement from Drive to Neutral
Shift lever inadvertently moves from Drive to Neutral during normal driving without driver pressing the shift button. Vehicle loses power and acceleration when this occurs. Shift indicator display continues to show Drive position even when vehicle is actually in Neutral, creating confusion and safety hazard.
When: At 80,000 miles; occurred while driving 30 MPH
Symptoms owners cite: Shift lever moves from Drive to Neutral without button press; Indicator shows Drive while in Neutral; Loss of power and acceleration; Discrepancy between indicated and actual gear
Repairs/costs cited: Vehicle not diagnosed or repaired
Recalls/TSBs owners mention: Manufacturer not notified
Transmission hard shifting and torque converter problems
Transmission exhibits hard shifts in lower gears and inconsistent shift quality. Torque converter clutch locks up hard and unlocks unexpectedly when decelerating on hills. When ascending another hill, engine speeds up then re-locks with a jerk. Slow torque converter lock-up and harsh lock engagement reported.
When: During hill driving and normal shifting cycles
Symptoms owners cite: Hard shifting in lower gears (inconsistent); Slow torque converter clutch lock-up; Hard lock-up when it engages; Unexpected unlock during deceleration on hills; Engine speed increase followed by jerky re-lock on hill ascent
Transmission failure without warning at intersection
Transmission fails suddenly and without prior warning while vehicle is at an intersection, nearly causing a collision. Occurs in 2007 Trailblazer SS model.
When: At intersection; no prior symptoms reported
Symptoms owners cite: Complete transmission failure without warning; Loss of transmission function at safety-critical location
Multiple drivetrain system failures and 4WD malfunctions
Vehicle exhibits recurring Service 4WD light and stalling in 4WD operation. Later diagnosed as bad front axle with 5 binding gears preventing safe 4WD operation. Vehicle also experienced Service StabiliTrac light and O2 sensor failure. Owner reported feeling unsafe in vehicle; Chevy offered only partial body-systems warranty coverage, refusing buyback.
When: First 4WD issue January 2009; recurred November 2010 after 19 months of intermittent use
Symptoms owners cite: Service 4WD light illuminates; Unable to engage 4WD; Vehicle stalls in 4WD mode; Bad front axle diagnosed; 5 gears binding; Service StabiliTrac light illuminates and resets on restart; O2 sensor failure
Repairs/costs cited: Second dealership diagnosed bad front axle requiring repair; O2 sensor replaced
Recalls/TSBs owners mention: First dealership (3-day inspection) could not identify problem and blamed snow in muffler; Chevy offered only body-systems parts coverage under warranty and refused vehicle buyback
Synthesized from 14 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 0 most recent
Had powertrain trouble with your 2007 Chevrolet Trailblazer?
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 2007 Chevrolet Trailblazer?
It's a documented issue but not catastrophic. 14 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?
Across the 13 complaints that reported odometer mileage, most powertrain failures cluster between 58,324 and 89,286 miles, with the median around 65,000. A quarter of owners report trouble before 58,324; a quarter make it past 89,286. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
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/2007/Chevrolet/Trailblazer.
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.