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I forgot to mention the OEM/ Stock 1 - 2 Shift Valve-Train design of the 4L60E Transmission Family...
The PCM and 1 - 2 Shift Valve-Train allow for an Up-Shift from 1st to 2nd Gear; when the Gear-Selector is in the Manual 1st-Gear Range.
In many scenarios, this is a good thing... as it helps protect both the Engine and Transmission from Over-Speed/ Revving.
The TransGo 4L60E HD2 "Shift-Kits/ Reprogramming-Kits" , provide a replacement 1 - 2 Valve-Train that does away with the Stock-Function/ Safety Feature that I mentioned above.
This is what TransGo means, by saying that 1st-Gear can now be held to any RPM (engine speed).
The TransGo 4L60E HD2 1 - 2 Valve-Train does have its place... I do like to use it when I convert the 4L60E to a Full-Manual Forward-Shift Valve-Body without the use of any Shift-Solenoids. I do Retain the EPC solenoid that operates with a TPS.
^^^ Is why...
In earlier threads about installing the TransGo HD2 kits, I have repeatedly suggested not performed step 5 (on Page 2) the HD2 instructions. The stock 4L60E/PCM provides some protection against overrevving on a downshift. Why take it away. You can tune the 1->2 upshift RPM and make it as high as you want.
^^^ Is why...
In earlier threads about installing the TransGo HD2 kits, I have repeatedly suggested not performed step 5 (on Page 2) the HD2 instructions. The stock 4L60E/PCM provides some protection against overrevving on a downshift. Why take it away. You can tune the 1->2 upshift RPM and make it as high as you want.
I of course agree.
It is much safer for the Engine and Transmission (with someone driving that does not understand what there are actually doing).
This feature has been around for a VERY long time...
Even the THM400 1 - 2 Shift Valve-Train is designed this way.
And again the TransGo THM400 "Shift-Kit" does away with this safety feature (just like the THM700-R4 and 4L60E).
If the customer has a Competition (Drag Racing) License or understands how the Transmission actually operates...
I have no problem removing this safety feature.
I normally ONLY remove it, when I convert these Valve-Bodies to "Full Manual-Shift" operation.
TransGo offers "Out-of-the-Box" parts and instructions to convert the THM400 and THM700-R4 units, to be Forward-Patter Full-Manual Valve-Bodies.
TransGo does NOT offer this for the 4L60E... except for rewiring the Shift-Solenoids and Pressure-Manifold-Switch.
I make my own version of a "Full Manual-Shift" 4L60E Valve-Body... It is completely HYDRAULIC, with no Shift-Solenoids.
Only the EPC solenoid remains.
These Valve-Bodies have been a HOT-ITEM for me!
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