Two problems related to transmission fluid leaking have been reported for the 2006 GMC Sierra 2500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2006 GMC Sierra 2500 based on all problems reported for the 2006 Sierra 2500.
I have a 2006 GMC Sierra 2500 with the lbz duramax and allison transmission. Two of the transmission coolant lines began leaking transmission fluid at the crimp ends in March of 2009. The truck only had 32,000 miles, but was 3 months beyond the 36 month warranty period. Service under warranty was denied. An on-line search reveals several others have complained about this issue and that the dealer installed oem replacement lines are no better (developing leaks soon after replacement), yet no TSB or corrective action has been issued by gm. Leaking transmission fluid is a fire and environmental hazard. The leaks are getting worse.
I own a 2006 GMC 2500hd duramax/allison crew cab. I took ownership in Feb of 2007 with 32k miles. Transmission lines were leaking at that time. Dealer replaced the lines under warranty. Now at 100k miles and same "new" lines are leaking once again. This is a flammable fluid and constitutes a potential fire hazard.