no..a shift kit firms up the shifts, on a tune without a shift kit an servos the tuner just bumps the line pressure if i remember correctly. im not a tuner by any means. i think the servos an 1 washer will be just right for you. remeber that 1 washer and those servos will help. risp up your tranny even though you put a stall. the more washers the harder the shift. so IMHO id do JUST 1 washer, the servos, the 4th gear servo an w.e else you have. change the seperator plate while your in there to a Sonnax hardened one. i think thats who makes it i can verify when i get home. the OEM one is soft an wears the holes out causing a soft shoft or a shift problem.
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2008 GMC CCSB 6.2/6L80e swap
Gen IV 5.3/60e swap 1994 ecsb W/T