Further update! I now have 20,000 miles on the 4T65E since installing the ZZP Shims, Dexron VI, and the 2 Long Double Stack Tranny coolers (18,000 GVW each!) outside of the radiator cooling. Today, I changed the fluid again with Syntec (Walmart) Dexron VI as well as the filter. About 6-9 months ago, I decided that I would purchase the Transgo shift kit and would replace the ZZP shims with the Shims and new springs for the 1-2, 2-3 accumulator since I felt that it was a more complete solution/kit than just the shims.
First, the transmission fluid (Dexron VI) looked really clean/good at this change-the fluid was really still looking very red (Like when fresh) and there was almost nothing in the pan-no metal particles/no silt. I was surprised!
I did remove the ZZP shims and installed the shims and new springs on the 1-2, 2-3 accumulator pistons from the transgo shift kit. Filled it up with 7.5 QTS of Dexron VI and went for a ride.
The 1-2 shift is definitely faster than before and so is the 2-3 shifts but unless you knew the difference before, you would not notice any harshness at all. It feels all very normal, unlike the transgo shift kit I installed last year on my 94 mustang GT convertible with the crap AODE automatic-that kit transformed the AODE into a very fast shifting auto with crisp firm shifts. Not the case here but not the objective either.
No harsh shifts as I would have expected at this point after the last 1.75 years since I started to attack this issue. I will keep all of you updated. Hope this helps!
