HMMM Ive had a 700R4 in my suburban(5500#s) for years behind a 400hp 383 with a 300hp NOS fogger in the intake w?3.90limited slip. After I started building them myself they started living. Funny I never could get a pro built trans to live past a yr. The only thing I have ever had a issue with was the 3/4 clutch pack. I upgraded that with a commercial unit with 9 clutches instead of 6. and it is right in front. pull the pump and slide a new one in.
Built it with red line clutches, kollen steels, 10 vane pump and corvette servos/accumulators. B&M valve body kit. More weight and I pounded on that thing and raced it. But I would agree if youre having issues go to a 4L80E. you can do alot with that trans but not cheap.

 

That would be the way to do it. I built mine with sonnax springs, and green clutches. I didn't want to sink a bunch of money into an automatic when I really wanted a 5 speed. Good call on my part because the MTV up shift valve seized up in the VB after a couple of miles and annihilated my friction unit.
I just put in the order for my wildwood floor mount pedal and master cylinder, and my 6 puck ceramic clutch and pressure plate.

 

yep incorrect tv adjustment is a big killer of the trans. Too low pressure and its slips he clutches and burns em up fast. Another reason i like a 4l80. Car adjjust everything from line pressure, to shifts, lockup etc.. And its basically a t400 with overdrive and electronics. Or.... Could always stick o gear venders overdrive unit on

 

those gear vendors are more than i paid for my engine, trans, and supercharger setup/mods combined.

the TV cable was adjusted perfectly. the problem was the MTV upshift valve which is entirely different.

 

I looked into Gear Vendors for an underdrive unit, it was over $2500. Would be great to have 3:91 or 4:11's at the flick of a switch. But to rich for my blood.
Having said that it is on the list. Not much more than changing tranny and gear set. Both fun and economical settings.

 

So did we grab the t5 yet? I wanna see this beast with a manual, which is what I advised you to do several years ago if you remember