As the subject suggests - I have recently had a full trans fluid flush on my 2000 model VTII Commodore LS1 (40000miles) with the 4L60E transmission. When I mentioned this on another forum http://www.ls1.com.au I had a reply from a member stating he believed he toasted the transmission in a similar type of car with the same box as he did the conversion to synthetic fluid at 30000miles.

Apparently when he approached Mobil - the manufacturers of the synthetic fluid he used, they claimed that you should only change from mineral to synthetic early in the life of a transmission, less than 8000 miles otherwise you will cause a premature end to your trans - here is a quote from the thread:

"no mobil didnt accept responsibility,they just suggested that maybe coz the box was run with mineral for that period and that i put synthetic it friction proofed the clutches and that you need special clutches to run with synthetic"

Does anyone have any informed comments or thoughts on this?