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 Hummer H3 powertrain problems
severe 15 complaints filed with NHTSA · avg repair $2,500 · see powertrain across all vehicles →
Failure mileage
Complaints
15
Recalls
0
Avg fix
$2,500
1injury
When does it fail?
Of the 15 powertrain complaints filed for the 2007 Hummer H3, here's the actual mileage breakdown — failures cluster heaviest at 75,000-100,000 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 9 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 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 PI bulletin advises the technician on the proper way to install the pistons in an engine.
full bulletin at NHTSA ↗This service bulletin provides a vibration analysis worksheet the technician can use in conjunction with the appropriate Vibration Analysis-Road testing procedure when diagnosing vibration concerns.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2007 Hummer H3 powertrain generates a cluster of interconnected failures that owners describe as returning problems despite repeated repairs.
Cylinder head cracking is the most common complaint. Owners report cylinder #5 misfire codes (P0300) appearing between 44,000 and 66,000 miles, linked to compression loss and small cracks in the head. One owner attributes this to soft metals in the cylinder sleeves and cites the same problem occurring in pre-2007 H3 and Colorado models. Repair costs around $4,500. Even after replacement, one owner's check engine light returned within weeks.
Transmission failure is widespread and unpredictable. Slipping and incorrect shifting can start as early as 25,000 miles without triggering codes—dealers refused service until gears actually failed. One owner faced transmission replacement at 65,000 miles, then needed another at 103,000 miles. Another experienced transmission fluid so hot it melted the filter and sprayed boiling coolant from the dipstick (causing second-degree burns). Torque converter clutch solenoid codes appear repeatedly.
Radiators crack in the top tank near the motor, typically between 46,000 miles and within months of replacement. When radiators fail, coolant contaminates the transmission oil cooler, destroying the transmission. One owner paid over $2,000 for a refurbished transmission and new radiator after this cascade failure.
Other recurring issues include broken valve springs (as early as 30,000 miles), blower motor resistors melting, PCM failure, and electrical gremlins. Owners consistently report dealers acknowledged these as known issues but refused warranty work.
Same Hummer H3 powertrain reports on nearby years: 2006
Failure modes owners describe
Cylinder Head Failure / Compression Loss
Multiple owners report misfire codes and loss of compression in cylinder #5, diagnosed as cracked cylinder heads. Owners attribute this to soft metals used in cylinder sleeves. Occurs typically between 44,000–66,000 miles. Repair cost cited as approximately $4,500.
When: 44,000–66,000 miles
Symptoms owners cite: Check engine light with cylinder #5 misfire code (P0300); Sudden reduced power; 90% compression loss in affected cylinder; Small crack in cylinder head
Repairs/costs cited: Cylinder head replacement; costs reported around $4,500. One owner reports multiple repeat repairs after dealer work.
Recalls/TSBs owners mention: No recall or TSB mentioned by owners. Owners note this mirrors 3.5L engine problems in pre-2007 H3 and Colorado models.
Transmission Failure / Slipping
Owners report transmission slipping, incorrect shifting, and complete transmission failure. Some failures occur without diagnostic codes, preventing early dealer intervention. Occurs from 25,000 miles onward. Multiple owners required transmission replacement or rebuild.
When: 25,000 miles and beyond; some failures at unknown mileage
Symptoms owners cite: Transmission slipping badly; Incorrect or delayed shifting in 1st and 2nd gears; Transmission slamming in reverse; Reduced power / stability control warning lights; Independent vehicle deceleration
Codes mentioned: Speed sensor pass/fail code, Torque converter clutch solenoid code
Repairs/costs cited: Multiple owners required transmission replacement or rebuild. One owner paid for transmission replacement at 65,000 miles, then faced second replacement need at 103,000 miles. Repair costs not consistently cited.
Recalls/TSBs owners mention: No manufacturer recalls or TSBs mentioned. Owners cite this as a known issue on Hummer forums.
Radiator Cracking / Leaking
Owners report cracked radiators developing leaks, typically in the top tank near the motor or frame lip. Occurs between 46,000 miles and within 10 months of replacement. One new radiator cracked again after only 10 months and 8,000 miles.
When: 46,000 miles; recurring within 10 months of replacement
Symptoms owners cite: Coolant leaks from top tank; Dried coolant spray across engine; Overheating that forced emergency pull-over; Cracks forming at frame lip or motor mounting area
Repairs/costs cited: Radiator replacement; one owner reported spending over $2,000 for refurbished transmission and new radiator when radiator failure contaminated transmission with coolant.
Recalls/TSBs owners mention: No recalls mentioned. Owners identify this as a known defect on Hummer forums. Dealers refuse warranty work on out-of-warranty vehicles.
Transmission Contamination from Radiator Fluid
When radiator fails, coolant leaks into transmission oil cooler, contaminating and destroying the transmission. Occurs as secondary failure after radiator cracking.
When: After radiator failure
Symptoms owners cite: Radiator fluid present in transmission; Transmission failure following radiator leak; Transmission oil cooler not operating correctly
Repairs/costs cited: Full transmission replacement required. One owner paid over $2,000 for refurbished transmission and new radiator. Radiator coolant damage not covered under warranty.
Recalls/TSBs owners mention: None cited; owners report this as a known issue on Hummer forums being ignored by dealers.
Misfire / Ignition Coil / Spark Plug Issues
Recurring check engine lights with misfire codes in cylinder #5. Owners replaced spark plugs and ignition coils multiple times without permanent resolution. Appears linked to underlying engine problems (cracked head, valve spring issues).
When: 44,000 miles and recurring thereafter
Symptoms owners cite: Check engine light with cylinder #5 misfire; Multiple misfire codes returning after parts replacement; Check engine light returning days to weeks after dealer clearing code
Repairs/costs cited: Replaced all five ignition coils and spark plugs; problem recurred. Multiple dealer visits failed to resolve.
Valve Spring / Rocker Arm Breakage
Valve springs (rocker arms) break prematurely, causing leaking valves. One owner reports mechanic found other springs fatigued with looser-than-normal seating. Occurs as early as 30,000 miles. Known issue on 2006–2007 Rendezvous per service manager.
When: 30,000+ miles
Symptoms owners cite: Power loss while driving 50 mph; Misfire in cylinder one; Leaking valve problem; Broken/fatigued valve springs
Codes mentioned: Misfire in cylinder one
Repairs/costs cited: Valve spring / rocker arm replacement required.
Recalls/TSBs owners mention: No recall cited. GM service manager acknowledged spring problem exists on 2006–2007 Rendezvous.
PCM (Powertrain Control Module) Failure
Engine stalling and loss of ignition control due to PCM failure. One owner experienced vehicle stall at 25 mph with inability to restart. At 119,000 miles, another owner had PCM replaced.
When: 119,000 miles (documented); stalling can occur at any mileage
Symptoms owners cite: Vehicle stalls without warning while driving; Unable to restart; Ignition control loss
Repairs/costs cited: PCM replacement required.
Recalls/TSBs owners mention: Manufacturer notified per complaint.
Transmission Fluid Overheating / Filter Melting
One owner experienced transmission fluid so hot it melted the filter and pressurized the dipstick, causing hot fluid to spray out with force. Transmission shop owner with 20 years experience said he had never seen transmission get hot enough to melt a filter.
When: Early in ownership (3 days after purchase); 80 miles driven
Symptoms owners cite: Transmission slipping badly; Excessive transmission heat; Melted transmission filter; Pressurized, superhot transmission fluid expelled from dipstick
Repairs/costs cited: Caused second-degree burns to owner's hand; emergency room visit required. Transmission shop rebuild needed.
Shifter Sticking / Key Lodged in Ignition
At 119,000 miles, owner experienced key becoming lodged in ignition, draining battery. Shifter replacement required to resolve.
When: 119,000 miles
Symptoms owners cite: Key lodged in ignition; Battery drain due to stuck ignition; Shifter malfunction
Repairs/costs cited: Shifter replacement required.
Recalls/TSBs owners mention: Manufacturer notified.
Blower Motor Resistor Failure / Overheating
A/C blower motor resistor overheats and melts, disabling fan. One owner reports this is a known problem for Hummers. Another owner's blower threw hot air when set to cold.
When: 65,000 miles (documented)
Symptoms owners cite: A/C fan stops working; Blower motor resistor overheating and melting; Blower throwing hot air on cold setting
Repairs/costs cited: Blower motor resistor replacement; one owner mentions separate installation to resolve. No cost cited.
Recalls/TSBs owners mention: Owner reports this is a known problem for Hummers.
Emission System Leak
One owner diagnosed with emission system leak after multiple check engine light returns. Dealer attempted repair but leak persisted.
When: Unknown mileage
Symptoms owners cite: Repeated check engine light; Emission leak detected on diagnostic
Codes mentioned: P0300
Repairs/costs cited: Dealer repair attempted but failed; leak recurred within a week.
Electrical System / Battery Issues
Vehicle experienced complete computer system failure and self-discharging battery that drained over 6 weeks in the shop without diagnosis.
When: Unknown mileage
Symptoms owners cite: Entire computer system failure; Battery self-discharge; Vehicle stopping suddenly while driving (25–50 mph)
Repairs/costs cited: PCM replacement performed for computer failure; battery drain issue unresolved after 6+ weeks in shop.
Transmission Shifting Issues (No Code)
Owner reports trouble shifting; dealer visited four times and claimed shifting trouble is a normal condition, refusing to investigate or provide service.
When: Unknown mileage
Symptoms owners cite: Trouble shifting
Repairs/costs cited: No repair provided; dealer stated this is normal.
A/C Control Panel Light Failure
A/C control panel lights no longer working.
When: Unknown mileage
Symptoms owners cite: A/C control panel lights inoperative
Synthesized from 15 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 2 most recent
Radiator leaking, hood vent coming up, a/c control panel lights are no longer working
Rebuilt transmission twice cleaned throttle body replaced exhaust manifold two o2 sensors replaced the radiator the heater core a fuel pump relay and this engine light still will not turn off it says torque converter clutch solenoid I'm disgusted already gm fix ur [xxx]. Information redacted pursuant to the freedom of information act (foia), 5 u.s.c. 552(b)(6). *tr
Had powertrain trouble with your 2007 Hummer H3?
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 Hummer H3?
It's a meaningful issue. 15 complaints have been filed and the failure mode causes operational problems for owners. Repairs average $2,500.
At what mileage does the powertrain typically fail?
Across the 13 complaints that reported odometer mileage, most powertrain failures cluster between 44,000 and 85,000 miles, with the median around 70,000. A quarter of owners report trouble before 44,000; a quarter make it past 85,000. 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/Hummer/H3.
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.