In the current 700r4 I've had zero issues with the 3-4, and is not a racing application, K1500/towing/4x4. Decided not to go with Sonnax Smart Drum or 4L79 or variant for cost and custom parts availability. Will install Sonnax reinforcement kit- but was wondering what parameters are met with deciding to go with their HD backing plates vs GM 4L60E thicker backing plates? There's very little info in search and I think Sonnax make some great parts- but they like promoting them also.

 

I used these same parts. you have to use the 4L65 set of frictions which includes an extra friction vs 4l60. an extra friction is a good thing.

https://www.sonnax.com/parts/4544-he...king-plate-kit

Designed for use with GM high energy clutch pack with seven .067" frictions and six .095" steels, this kit can be used to upgrade OE 700-R4 and 4L60-E five-friction or six-friction clutch packs to seven frictions, or to improve stock, seven-friction clutch packs in 4L65-E and 4L70-E units by reducing backing plate flex.

i think i used GPZ clutch setup for 4L65E. ended up having to pick up a couple frictions in a thicker thickness to get the perfect stack (0.080? 0.105"?, don't recall exactly) Few bucks from local supply house.

this is in my OBS 4x4 4L60E and I use it for towing. I also used the reinforcement kit.

 

I guess they work.......until they don't
Been told that the thicker oem backing and apply plates will work well for my power- will use BW or GPZ in that clutch pack with the reinforcement kit as well. This is for a 89 K1500 which I'm slowing working towards a 24X 0411 conversion.