If you're going to do just the Sonnax valve and tricumulator springs, here's a tech bulletin from Sonnax about what else they have available for the 4R100's.
http://www.sonnax.com/tech-articles/TB-VOL1-NO6.pdf

An FTE-sponsor source of the kit we need for ours is:
http://www.puredieselpower.com/catal...-kit-p-85.html

BTW, I did just the Sonnax and springs about four years ago and am still quite pleased with the much better shifts. I have not felt the need for more, though I don't tow heavy and have nothing to compare mine to. I know there are better performers out there, but I haven't needed anything at that level.

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