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Is that shift kit you mention Transgo 4L60E-HD2 ?The Sonnax fix requires a new oversized valve and a reamer to enlarge the bore. Most rebuilders just do what the YouTube video shows. Sometimes they use the long spring or sometimes they use a piece of tubing or anything between the two PWM/TCC valves. It's an easy fix that essentially stops the PWM (pulse width management) valve from working. The valve is constantly working back and forth so quickly that it's almost a vibration. That's why the bore wears out. GM likes their Torque converter clutches to have a controlled slip for smoother apply and operation. This creates problems down the road. Any transmission rebuilder with any sense will block the valve with any rebuild. Transgo has a slightly oversized valve and a stiff spring in their shift kits and they work just a good as Sonnax at a fraction of the cost. You will barely notice the fix except for a slightly firmer 3-4 shift. I did the Transgo kit to mine and I love the firmer 3-4 shift.
I don’t know about the HD2. It’s the cheaper kit though. It isn’t the reprogramming kit that can make it shift really hard.
Yes. HD2 is the reprogramming kit. Oops, I was wondering if this would be appropriate for a daily driver. Sounds like the answer is no.I don’t know about the HD2. It’s the cheaper kit though. It isn’t the reprogramming kit that can make it shift really hard.