What do the guys that know about valve body's and clutch engagement think about adding this to an older unit? Seems conterintuitive but then I was reading that it helps with harsh downshifts and that's what caused my 456 shaft to give up.

 

I did it on mine when I rebuilt it per the GM TSB. So, I am pretty sure that along with all the supposed Sonnax "upgrades" and "fixes" they advertise are mostly just hyping not so existent problems. So after I rebuilt it seemed like it was more "luxurious" and the driving experience was improved because of less clunks and clanging especially like you said when coming to a stop, especially in certain faster than normal stops right after upshifting in stop and go driving scenarios. I am sure now this was just placebo. The thing about these its always so random when it wants to do clunks and clangs. The accumulation of backlash with mine being an AWD amplifies the clunks and clangs more I think especially when the transmission wants to do a low throttle/coasting upshift/downshift when the drivetrain is transitioning in a neutral floating state which then when you get a transmission shift and the on-coming/off-going isn't perfectly synced then you get a really fast torque reversal that reverberates through the drivetrain.

So basically, it didn't seem to do anything with me just trying to observe it although of course when I initially did it seemed to be better shifting but that was probably placebo. For as cheap as the parts are I would buy the new separator plate GM part number and throw in the extra checkball while you are there. In theory the design change seems logical. If I remember I think it had something to do with the release of the low/reverse clutch after the solenoid that controls it turns off? or maybe it was something else? I didn't think it had anything to do with the 456 clutch but I need to go re-research it and see.

 

I don't know but I would do it if it would fix whatever the heck is going on with mine.

Getting on the brakes lightly while turning into a parking lot from road say 20mph or so then lightly getting on the throttle to turn back the opposite way down an isle and its like the truck hesitates (not really revving like its slipping I don't think) and then shifts and goes on like normal. Sound like the same thing this solves?

If it matters 5.3L/6L80 with 4.56s and 33" tires.

 

No, it gets rid of harsh downshift. I added it, just got it back today. Seems to shift down harder into 2nd and 1st now so whatever...

 

@smokinlmm You already got your trans back in?

 

Just got it back together yesterday, just in time for that stupid hurricane.

 

That seemed rather quick

 

I bought the stage 4 parts and had my local guy install it.