definitely annoying
Crashes / Fires:
0 / 0
Injuries / Deaths:
0 / 0
Average Mileage:
29,788 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.

2006 GMC Sierra 2500 transmission problems

transmission problem

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2006 GMC Sierra 2500 Owner Comments

problem #4

Jan 152008

Sierra 2500 4WD 8-cyl Diesel

  • Automatic transmission
  • 36,500 miles


Transmission cooler line leaking transmission fluid at an aluminum crimp that connects a rubber hose to the transmission cooler; an inferior design. As such, a transmission oil leak is a fire hazard. I am aware of two car fires that were caused by leaking transmission cooler lines. The last one involved a Ford Taurus station wagon where the owner had the transmission rebuilt by his local transmission shop (a national franchise transmission repair shop) and they cross-threaded the lower cooler line at the transmission. The transmission fluid leaked on to the exhaust cross-over pipe and the car burned to the ground on the side of road in the interstate. The owner's insurance company subrogated against the transmission shop for the damages. Fortunately, no one got hurt, but they came close.

- Owings, MD, USA

problem #3

Jan 032008

Sierra 2500 8-cyl Diesel

  • Automatic transmission
  • 30,000 miles
I have a 2006 GMC 2500hd that has 31000 miles on it. The transmission cool er lines are leaking and the dealer has been notified about this problem. The new parts are on backorder, meanwhile the truck leaks transmission oil on the ground which could be a potential fire hazard alone with an environmental hazard. Many GMC 2500hd owners are having this problem. This is not yet a recall but needs to be addressed.

- Breaux Bridge, LA, USA

problem #2

Jan 302008

Sierra 2500 4WD 8-cyl Diesel

  • Automatic transmission
  • 27,650 miles
Went to GMC dealer because truck has a transmission oil leak. Technician noted that all three transmission oil cooler line are leaking. According to internet forum (dieselplace.com/forum/showthread.php?T=202078), this is a know defect on the 2006 Silverado and Sierra trucks equipped with diesel engine and allison automatic transmission. Several owners have had 2 or more incidents. Replacement lines are no better than the originals. I am an engineer and have been involved in vehicle fire investigations in the past, some were caused by leaking transmission cooler lines dripping on hot exhaust pipes and manifolds. This is a potential fire hazard! this requires a new design for these transmission oil cooler lines.

- Lansing, MI, USA

problem #1

Jan 182008

Sierra 2500 4WD 8-cyl Diesel

  • Automatic transmission
  • 25,000 miles
I have a 2006 GMC Sierra that has had transmission lines replaced and that keep having to be replaced because of hose leaking every year.

- Waretown, NJ, USA

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