Like I stated above, with the ZZP shift kit installed and with a 28,000 lbs GVW trans cooler installed which does all of the transmission cooling now (no lines into the radiator), I have had zero problems since early December 09. I used the 1/2 inch spacer recommended by ZZP on the 1-2 spring in the accumulator and also a 1/2 inch spacer on the 2-3 spring in place of the 3/4 inch spacer recommended by ZZP on the 2-3 spring since I wanted to have the softest shifts that could fix the problem which it did. I would have tried the 3/4 inch spacer on the 2-3 spring if my set up did not fix the problem. My transmission has 100,000 miles on it. I think that your assessment that the springs in the accumulator weaken with age and heat is correct and the reason for the hard shift problem in these transmissions most of the time, not the PCS solenoid replacement recommended by many trans shops and very expensive, assuming everything else is in good condition in the tranny which in my case, I knew was correct. Change the fluid to Dexron VI (Supertech frm Walmart is the cheapest), change the filter, and I would recommend the biggest tranny cooler in the grill separate from the radiator which heats up the fluid unnecessarily, and I expect 10's of thousands more miles from my 4T65E. Let us know how you make out!
