I'm looking at adding a turbo to my 2001 Chevy 1500HD and the common upgrade for the 4L80E transmission above 500HP is to add an HD2 shift kit. Is there anything in that kit that I can't do tuning in HPT? The only thing I see is the pressure relief valve, which is weird in the HD2 kit and I was planning on using the Sonnax boost valve, which does the same thing, instead. Pressures and shift times are easy enough to change in HPT, so what am I missing? Thanks.
Last edited by pknowles; 10-25-2019 at 08:10 PM.
Phil K.
02 Camaro SS 5.7L LS1
01 Silverado 1500HD 6.0L LQ4 4L80E 78/75 turbo with Flex Fuel
The thing is, with a stock trans, if you set Shift Timing to 0.00 and raise shift pressures, logging 'time of latest shift' will show it still takes .300-.350 seconds from start to finish. That's as fast as all the little stock-sized holes in the separator plate and various valve body passages will let the pistons apply.
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