Anyone here using a 700r4/4L60e with the Sonnax close ratio gear set planetary unit? Has a much more favorable spread to the gearing for performance applications. And said to be able to take a healthy amount of power. https://www.sonnax.com/parts/3734-2-84-ratio-input-carrier-kit
Imo that's beginning to be diminishing returns. That's $700 ? Still have the 3-4 beast shell upgrade if you're serious about it lasting. If you need the strength go to 4l80e and buy the controller with that $700. It has the th400 gear ratio, only downside is a.75 od. I've run a 700r4 so they can last a while behind moderate power, but by your second refresh you could buy a 4l80e.
I think the sonnax smart shell is far better than the beast. Last few beast shells I bought came boxed in a package with Chinese writing, and is noticeably lighter than they use to be. Raybestos Z-PAC is probably the best setup for the 3-4 clutches. The problem with the aftermarket 8 or 9 clutch kits it the thinner clutches and steel plates. The thin plates don’t radiate the heat as well, causing them to warp. The raybestos kit has 11 one sided frictions, adding more clutch capacity with thicker hair plates. I haven’t used the sonnax gearsets yet, but I have to agree with the above comment. You can build a 4L60 with all the fancy frictions, input housings, gearsets, servos, band, etc, and it will still be weaker than a stock 4L80 with a shift kit. If you absolutely have to have overdrive, assuming you can make it fit, a 4L80 is the way to go. Use the money you would spend for the gears for the controller.
You might get the gear spread but you still only have the other internals to do about 5-600hp. The stuff just isn't that robust. As above, if you want reliable and longevity, 4l80e or th400 with a gear vendors. If the car is light enough a powerglide and gear vendors is a nifty setup to get the overdrive.
