[Ironangel]

Anytime you get a chance to read any of Clinebarger's posts or comments you should take them to heart! He was directly involved in the development of the Turbo-Hydramatic transmissions when these trucks were still rolling off the lines. Just thought I'd throw that in since you posted that old thread. You have to be careful who you listen to on these forums. He taught me via this forum, how to rebuild a Turbo-350 so I'll pass along a bit of that knowledge...Your on the right track with the Superior Solutions shift kit. I was about to point you in their direction, compare the price, bet you paid more?https://www.ebay.com/itm/TH350-TH400...item3f0ef6bb1e The fact that your trans. quit shifting after you installed the lighter springs indicates more of a problem than just the lighter spring change. Did you back out that adjusting screw in the modulator? Remember that the modulator works in conjunction with the governor by holding off shift points by raising line pressure. I'm suspecting that the present screw adjustment in the modulator has rendered the governor useless with the light springs installed. Back that screw out and try it again...1/4 turns make all the difference in those red stripe modulators...Let us know what you find. I have some notes out there in the shop (somewhere) on tuning governor for a 69 L34 396 BBC as I dialed one in to make both shift points occur at 5900 rpm @ WOT in the truck shown in my avatar. (72 C/10 SS COPO) "Modulated pressure & Governor pressure work against each other on the shift valves....Adjusting the Modulator allows Modulated pressure to overcome Governor pressure at a higher manifold vacuum & hold-off upshifts...
If you lower Governor pressure via springs...It WILL do the same thing, But without the side effects of higher Modulated pressure." Gospel!