The 6F55 trans employed in the SHO platform has proven itself to be quite stout, and takes a decent, repetitive pounding.
Earlier years, mostly 10's-12's, did present minor issues, in which TSB's were issued. IIRC, something about check balls in the valve bodies needing replacing or something.
Power wise, the engineers whom developed the SHO platform, I spoke with in person during one of my (now several) tours of the CAP assembly plant, stated in a general sense, that the 6F55 did not start presenting failures until "around the 720hp" mark. 720 at the crank that is.
I have run mine with the "lower" of two track files I have (lower being 525awhp / 680 crank) and have not experienced any problems.
The trans & ptu are about the only things that I haven't modded in my SHO, & I was, up until this past Spring, daily driving it, drag stripping it. Not to mention all the "spirited" driving whilst running into the occassional prey out on the street that fell victim to it's prowess and fortitude. Lol. I now reserve it's use mostly for shows, or track use. Remember, the SHO's are a somewhat rare animal out there.
Anyhow, regular maintenance in the form of fluid changes is tantamount to longevity. An accelerated schedule is highly suggested, especially when one starts increasing the power and torque curves, as it's peanuts in comparison to outright replacement.
Their have been quirks along the way which were reported/experienced, but in the grand scheme of things, overall they are uncommon.
Hope that sheds some light into your query, and good luck if you decide upon picking one up. Welcome aboard!
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