NHTSA Complaint #10390385 — 2005 GMC SIERRA 2500

GM STATES THAT DEXRON-VI IS FULLY BACKWARDS COMPATIBLE WITH ALL DEXRON-III APPLICATIONS. MY VEHICLE IS A 2005 GMC SIERRA K2500HD, WITH AN 8.1L GASOLINE ENGINE AND ALLISON 1000 TRANSMISSION. AFTER PERFORMING A ROUTINE SERVICE ON MY TRANSMISSION (FLUID DRAIN AND REFILL), REPLACING THE DEXRON-III WITH DEXRON-VI, I NOTICED THE SEALS AND GASKETS LEAKING FROM AROUND THE TRANSMISSION. UPON FURTHER RESEARCH, I FOUND THAT THE SYNTHETIC DEXRON-VI IS NOT COMPATIBLE WITH CERTAIN SEALS INSTALLED IN ALLISON BRAND TRANSMISSIONS. ALLISON TRANSMISSION DOES NOT APPROVE THE USE OF DEXRON-VI IN ITS TRANSMISSIONS DUE TO THE SEAL INCOMPATIBILITY (ALLISON SERVICE TIP #1099P). ANOTHER ALLISON DOCUMENT (SA5429EN) LISTS TWO SERIAL NUMBER CUTOFFS, PRIOR TO WHICH CONTAIN SEALS INCOMPATIBLE WITH DEXRON-VI. THE SITUATION HAS YET TO BE RESOLVED - GM DENIES ANY POSSIBLE INCOMPATIBILITY, AND WILL NOT WARRANT ANY DAMAGES, WHILE ALLISON REPRESENTATIVES HAVE TOLD ME THAT THE PROBLEM IS A DIRECT RESULT OF DEXRON-VI. THE ESTIMATED COST TO REPLACE ALL OF THE SEALS IN THE TRANSMISSION IS $1,900.00. *TR