Redneck C4 2 years and counting. Never been into it. Ran their 3500 stall for about a year and a half. Ran some 10.5s @ 128 w/ my HCI 302 w/ a MP T70, 3.27s. New 351 setup, same tranny, same convertor just restalled (tightened it up, was blowing through it), spragless, 3.08s 10.1 @ 141 w/ crappy 60' do to slipping traclok.
I run 2 tranny coolers seriesed together, 1 is a B&M super cooler in the factory foglight location and another cheaper one like from Advance b/w the intercooler and radiator. I never see higher than like 170*and thats highway driving. I drive 7 miles to work and the needle doesnt even rise lol.
Im not saying the TH400 isnt a superior tranny, cause it is. But saying "every" C4 wont hold up to some power isnt entirely true, well so far it has worked for me. But there are definately many factors. Parts used, builder, etc.
1967 Mustang Coupe
1990 Mustang GT Turbod DD
1987 Mustang GT Turbod-9.75 @ 140mph gone but not forgotten