Automatic harness to T56
11-01-2009, 07:52 PM
#1
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Automatic harness to T56 I have a harness from an automatic and I built a relay box for a standalone but want to run a T56. What relays or other mods do I need to make to this harness to run a T56? Do I need a T56 computer or will either work? It is a '98 motor and I need to buy a computer soon. Also, I saw a 00' computer and harness online for $200, should I just buy it and convert the motor over to a 2000 model?
11-01-2009, 10:19 PM
#3
The only thing electronic on the T56 that is absolutely needed is the VSS. Plug should be the same from the automatic. There are 2 solenoids on the side of the T56. One is the skip shift, which you probably don't want functioning anyways. The other is a reverse lockout. The computer in its factory function will inhibit reverse engagement over a programmed vehicle speed. It does this by electrically turning OFF the rev lockout sol. So with no power applied, you can not shift to reverse. Some people have just wired this solenoid to a key power, or rigged a micro switch on the shifter if they like the safety aspect of it.
One side of the solenoid goes to 12v+ key. PCM supplies GROUND on other side of solenoid.
On 1999 and UP PCM, the pin location is C2-RED Pin 44.
On 1997,1998 LS1 PCM, the pin location is C1-RED Pin 42.
Computer needs programmed for the change in VSS pulses, Automatic trans had 40 pulse per driveshaft revolution, the T56 only has 17 pulses. Also changes to how the PCM controls the idle is needed, this prevents the PCM from quickly trying to change idle speed when you start to let out on clutch. By putting a manual trans calibration in your pcm takes care of both of those.
One side of the solenoid goes to 12v+ key. PCM supplies GROUND on other side of solenoid.
On 1999 and UP PCM, the pin location is C2-RED Pin 44.
On 1997,1998 LS1 PCM, the pin location is C1-RED Pin 42.
Computer needs programmed for the change in VSS pulses, Automatic trans had 40 pulse per driveshaft revolution, the T56 only has 17 pulses. Also changes to how the PCM controls the idle is needed, this prevents the PCM from quickly trying to change idle speed when you start to let out on clutch. By putting a manual trans calibration in your pcm takes care of both of those.
11-02-2009, 04:55 AM
#4
You can shift into reverse without having the lockout powered up. You just have to overcome the spring pressure against the shifter. It will work fine without being plugged in, and will have enough pressure against the reverse position that you won't accidently hit reverse while moving.
