but you would put in a shift kit that will stress the seals more with worn out fluid, well 12qts any way dropping the pan doesnt even get half out. I want a serious reason not to flush a trans with old/bad fluid with new after "X" amount of miles? I had a trans with 12,000miles burn up, miles mean very little to transmissions(to a degree, abviously 1,000,000 miles is going to have a signifcant amout of wear) fluid condition, temp and amount of abuse are how transmissions should be serviced. Also the best way I can describe it is would you after 100,000 miles just change the filter and 1 qt of engine oil, I hope not.
shift kit only increases line pressure in the trans, witch tightens up the clutch packs, a good thing, and transmissions run on ATF "trany fluid" not oil, once your fluid is all brown and burn up, its already on its way out, and if you remove all the fluid and put new fluid in there, it will most likely stop working, very fast.
why? because all the clutch material thats in the brown burn fluid is all thats holding the trans together, so dropping the pan and replacing 8 quarts its a nice trade off, and the shift kit will tighten up the shifts for ya.
but like i said if its brown its already on its way out, cars with lots of miles and burnt up brown fluid, some never leave the shop bay after a flush some get lucky and its fine for a while, so flush it you want, but best left alone.
if you got over 100,000 miles and the fluid is nice and red and dont smell, by all means do a flush, the fluid tells the whole story here. red fluid means someone took care of the car and had the fluid changed over the years, brown fluid means neglect and abuse.
and if you blew a 12,000 mile old trany up you really beat the crap out of your car, or the last owner did, well someone did lets say that.
and im sure it blew due to hot operating conditions from beating on it. heat is one of the killers for a automatic transmission, next is not doing regular fluid and filter changes.
