I have 41,500 miles on a 98 Z28 a4, no noticable problems but I went ahead and had the tranny FILTER changed and fluid changed instead of the GM recomended flush ONLY. I feel this was a good idea and since having this done it seems smoother all around. Maybe this was in my mind ONLY but some friends of mine have told me this was a waste of money AND it may cause problems.............ANY IDEAS here????
NOT synthetic just GM fluid....

 

I was about to change the tranny fluid and filter at a local garage when the Chevrolet dealer gave me some good advice. Have the tranny "Power Flushed" at your Chevrolet dealer. They do not replace the filter however they use a vacum line which actually removes the fluid from the torque converter area as well. The "Power Flush" actually uses hydraulic pressure to clean out your ENTIRE transmission system. This allows a greater amount of NEW transmission fluid into your system including fresh fluid in the torque converter area. If you drop the pan, you only change a minimal amount of fluid. The cost of a "Power Flush" at your Chevrolet dealer should be around $185.00, but well worth it. You should do this every 15,000 miles and change the differential at the same time which is an additional $80.00, or save the money and do the rear your self, but the tranny should be done with the "Power Flush" machine. The tranny runs and shifts like she just came off the lot!!!!