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NHTSA — Power Train Problems


really awful
Crashes / Fires:
0 / 0
Injuries / Deaths:
1 / 0
Average Mileage:
62,793 miles

About These NHTSA Complaints:

This data is from the NHTSA — the US gov't agency tasked with vehicle safety. Complaints are spread across multiple & redundant categories, & are not organized by problem.

So how do you find out what problems are occurring? For this NHTSA complaint data, the only way is to read through the comments below. Any duplicates or errors? It's not us.

2007 Hummer H3 drivetrain problems

drivetrain problem

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2007 Hummer H3 Owner Comments

problem #12

Apr 092016


  • 103,306 miles


The vehicle just lost power and almost lost ignition while driving 50 miles an hour. Diagnostic code state, misfire in cylinder one. Valve springs ( rocker arm) are breaking prematurely causing a leaking valve problem. Mechanic also noticed other springs were fatiqued causing a looser than normal seating. GM service manager mention a spring problem on 2006 2007 rendevous. One of the largest complaints with the Hummer 3 is this leaky valve syndrom which the dealers know about. Some occuring with the vehicle having only 30,000 plus miles.

- Southfield, MI, USA

problem #11

Nov 122014


  • miles
First the entire computer system stopped working. Had to replace thr PCM. Then my blower started throwing hot air when on cold. Had to install separate to resolve that issue. Had to re-build the transmission twice due to leak of coolant into the transmission. This truck has been a nightmare so far.

- Richmond, TX, USA

problem #10

Dec 012014


  • 94,000 miles
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).

- Houston, TX, USA

problem #9

Dec 212014


  • 53,018 miles


Noticed radiator fluid dripping underneath vehicle. Opened the hood and found radiator coolant had been blown all over interior engine compartment. Enough coolant remained in the reservoir to prevent overheating. I noticed the incident just in time.

- Severn, MD, USA

problem #8

Aug 182014

H3 5-cyl

  • 57,534 miles
My vehicle has a cracked radiator and according to other Hummer owners this is a common defect that happens to these vehicles. His over heating cuased me to pull over on a busy highway were I could of been hit and killed, total failer of vehicle electronics, GMC does not want to work on the vehicle that is not under warranty, because of the many problems wth this vehicle. This crack is were it is wearing near the motor.

- Palm Bay, FL, USA

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problem #7

Apr 012014


  • 85,000 miles
Less than 1 year ago, I had the radiator and transmission replaced in my vehicle. I have recently noticed the smell of antifreeze coming from my hood after long trips. The radiator that was installed in my vehicle 10 months and 8K miles ago has developed a crack in the top tank. There is dried coolant spray across the top of my engine and a crack forming right behind the lip of the frame of the truck.

- Deerfield Beach, FL, USA

problem #6

May 012013


  • 70,000 miles


My radiator tank cracked right across the top compromising my cooling system. This turned into a bigger problem as the transmission oil cooler was not operating correctly and eventually destroying my transmission. I had to spend over $2K to have a refurbished tranny and new radiator installed.

- Deerfield Beach, FL, USA

problem #5

Aug 022010


  • 44,000 miles
44,000 miles check engine light came on. Took to dealer I had a cylinder 5 misfire code P300 couple thousand miles later my truck was still showing multiple misfires. I had to replace the radiator because it was leaking and thermostat at 46,000, April 2011 at 65,000miles my transmission went out completely and had to be replaced July 2012 air stop working took to dealer they said I had to replace the fan blower motor resistor. Researched and founded this was a known problem for Hummer the motor gets to hot and melt causing the fan blower to go out. Several months later check engine light came on several more times took to the dealer said they couldn't find problem and cleared code my check engine light came on again so I took to auto zone diagnostic showed cylinder 5 coil multiple misfire so I had spark plugs changed alone with all five ignition coils. Couple months later check engine light came on again took it to dealer diagnostic test reveal code po 300 again and couple other codes dealer said my truck had an emission leak. Multiple misfire, cylinder 5 and a small crack in the head. I didn't understand how that magically happen. I paid the dealer to fix this on March 2014. A week later check engine light came on again. Took to dealer diagnostic showed emission leak apparently they didn't fix it the first time. Week later check engine light came on again took to dealer and diagnostic test reveal torque converter clutch said I need transmission replaced. I'm confused at this point the dealer put a newtransmission 3 years truck has never been over the road. I only drive locally. Now at 103,000 miles the dealer is saying I need another transmission. Something is not right here. After researching I've found thousand of Hummer owners experiencing the same problems I've experienced. Something needs to be done to protect consumers.

- Arlington, TX, USA

problem #4

Jan 262010

H3 5-cyl

  • 66,000 miles
I own a 2007 Hummer H3 with 66000 miles on it. It has been diagnosed as having a bad head due to the use of soft metals for the cylinder sleeve. Due to this, there is sudden reduced power. The cost of this fix is about $4500. My truck began with a check engine light on (autozone) said it was a misfire on cylinder #5. I went to the local dealer and asked them to look at the truck. They diagnosed it as a #5 cylinder having the compression leak of 90%. in looking on the internet (at Hummer forums), I observed that quite a few Hummer H3 owners were writing in about their experience with misfires and bad heads, at about the same mileage. I think this needs to be looked into and that GM should be ordered to do a recall. This is the same problem they had with the 3.5L engines they used in their pre-2007 Hummer H3 and Colorado. I am going to write my congress rep and ask that with the problems that GM is having right now, that this also be moved forward and that they order an investigation. Any other Hummer H3 owners with the same problems should do the same thing.

- West Bend, WI, USA

problem #3

Oct 292013

H3 5-cyl

  • 71,386 miles
I was driving on the express way when I noticed my engine rev real high. I looked at the RPM's and it was almost red lined. I let off the gas imediatly and came to a slow crawl and found that it would not shift out of second gear. Pulled it off the road and shut it off to get out to find that there was transmission fluid and radiator coolant pouring from the transmission. Had it towed to a mechanic to find out that the radiator was bad which caused the transmission and coolant to mix between the two. This causing the transmission to be destroyed along with the radiator. For this vehical being this low on miles this should have never happend. GM has made a faulty radiator and something needs to be done.

- Ravenna, OH, USA

problem #2

Jun 292013

H3 5-cyl

  • 84,278 miles
Had purchased vehicle 3 days prior from individual. Drove to el paso TX1 approximately 80 miles drove around town doing errands. Transmission started slipping badly, I pulled into a wal-mart and went to check the transmission fluid. Vehicle had a compression type dipstick. When I touched the lever on the dipstick it shot up approximately 8 inches and showered my right hand with very hot transmission fluid. This caused second degree burns to the palm and fingers, this made a trip to the emergency room necessary. The owner of the transmission shop told me that in his 20 years in the business he had never seen a transmission get so hot as to melt the filter. This one had melted the filter.

- Sierra Blanca, TX, USA

problem #1

Jul 032009

H3 5-cyl

  • 25,000 miles
This vehicle has had transmission issues since 25,000 miles. No code ever indicated so dealers would not investigate transmission until 1st and 2nd gears failed. Problem of incorrect shifting continued with several stops at the dealership. No code no service. Now the transmission slammed in reverse initiating a code (speed sensor pass/fail). After agreeing to replace the portion of the transmission that contains the shorted speed sensor, it was discovered the transmission was contaminated by radiator fluid. Now the radiator, not covered by warranty, also must be replaced with the complete transmission. Researching Hummer forums, this is apparently a known issue with the speed sensor and radiator contamination that is being ignored.

- Las Vegas, NV, USA

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