The increased temps, accelerated wear, and soggyness are all things you get with pwm...and you get worse fuel economy too

Those things go away with the on/off style lockup

 

Yes the PWM torque converter is backwards compatible.

Why would you have reduced fuel economy? With The TCC ON/Off you will have less slipping therefore better economy. IIRCC the PWM was more for comfort than anything. With a higher stall TC and the TCC set up to be ON/Off, the TCC lock up will more feel like another shift. You don’t get that feel so much with PWM.

 

I have read some magazine articles and websites that have said that PWM on/off causes harsher shifting and reduced fuel economy. I'm not saying i'm correct - remember i'm a complete amitaur here, just been doing lots of research on the subject because I've always been fascinated with Auto transmissions operations (secretly wish I could get into the industry to be honest)

Taken from the Sonnax website:
"...on/off operation had some shortcomings. Switching the TCC abruptly can result in a harsh apply sensation and adds unnecessary stress to driveline components. And while fuel economy improves with TCC operation, it can be increased further with a different control process. For these reasons the PWM control strategy was introduced. This control scheme eliminated the on/off feature in favor of a gradual apply/release function."
Source: https://www.sonnax.com/tech_resource...-modifications

This is just one source of several I have read, happy to provide more sources if you want. This is the reason why I thought using the reamer tool would make sense.

So my question is, is the sonnax website wrong and lieing to the public to try and sell their expensive tool?

TIA

 

i have had the TG kit and the sonnax kit....been so long since i had the TG kit i cant remember how the shift quality was on the TCC lock up was...but i never really enjoyed the TG kits shift quality overall ......but i can remember how the sonnax kit was.....very firm.....now i have installed the sonnax over sized valve with the sonnax shift kit and i can say the firmness is less harsh than before.....still firm mind you but more to my liking at least

my .02

 

The PWM application where you might gain some fuel economy is when the TCC will partially apply at rpm where it could not normally apply on/off because it would bog/feel very harsh.

Any time any tuning is done this is changed anyway because of the other reasons ive mentioned earlier.
Also, at cruise speed, with PWM there is always about a 40 rpm slip introduced on purpose. why? Couldn't tell ya...but that's straight from the gm principles of operation manual. So, I think what you might lost at partial throttle low speed apply...you'll probably gain at cruising speed.

Long story short...on/off is the way I will always build my units. I know many others agree. If you want to do it your way, that's totally cool by me. Just make sure the bore vacuum checks good and make sure you have a good cooler and change the filter more often because the converter clutch will wear faster with pwm

 

Keep in mind when they say "harsher shifting" they mean relative to stock, which is designed to be almost imperceptible. There are shifts where it's like someone rear-ended you and will definitely cause premature failure of hard components, usually because there's a problem with the transmission but there are certain combinations of parts where you can do that yourself. I don't remember which brand it was but there was a servo that I've seen not recommended for use unless you've upgraded certain hard parts like the output shaft because of how harsh the shifts become.