First of all i dont recomend putting any additives in that transmission.Most of the time those cars shift hard is because of a bad pressure regulator in the valve body.You have to replace the valve body and air check the clutches with compressed air.Before you do that do you have any codes in the computer?If you havent checked you need to do that now.You also will have to do a pressure test on the transmission its best to do a step pressure test but you cant do that without a scan tool without the special test software.You have to atleast do a high low pressure test but you will have to buy a transmission pressure tester.I recomend the otc one that does oil and transmission fluid pressure thats the one that i have I got mine at http://www.tooltopia.com its reasonable about 60 something i think.You will also need a air compressor and a rubber blow tip nozzle to air check the clutch packs later.

Answered by saturntech9 (expert)
23,388 answers provided