nj02z

iTrader: (6)

Are there performance gains (ET wise) to be had by switching to a built trans from a stock trans ? If anyone has picked up some Et with the switch how much? Or are you just gaining some reliability?

NorthTexasConverter

It wildly depends on who/how the transmission was built and what transmission in question. You're definitely gaining a lot of reliability getting a built transmission over ANY stock transmission, even a TH400 or a 4L80E, and depending on the the parts used, there may be marginally improved ETs. Some transmissions can be setup with aftermarket gear ratios which, depending on the setup, will definitely improve ETs.

mrvedit

A stock trans with a stock tune might take 1/2 (500 ms) second to perform a shift and power is lowered during the shift to preserve the trans. You aren't accelerating much during the shifts.
In contrast a well-built trans can shift in less than 100 ms with a proper tune; you will be accelerating almost the whole time.