I just put in my t56 into my 91z28 today and need to know how the wiring gets hooked up. i already checked the board and with no luck. my car has an electric speedo. where do the wires that where connected to the t5 go on the t56.

 

the speed sensor plug on the t56 is different than what is on your car. you just have to splice the wires and connect them. also, i think you might have to get a converter box to convert the signal so your speedo reads correctly

 

You need a speedo interface...
http://www.dakotadigital.com/products/interface.htm
Instructions say to use output #4 or #5 depending on the year. I had to use output#3 to get it to work.

You need some plugs too... My backup light connector fit, I just spliced in some wires to lenghthen it - it's the plug in the middle of the passenger side of the tranny. The shifter connector is for the reverse lockout... mine's wired in with my line lock on my hurst T-handle with the red button - it's the big solenoid up near the shifter. The speedo plug is the small connector under that. The CAGS doesn't get hooked up - it's the big solenoid on the drive's side in the middle of the tranny.

12101857 1 Shifter connector
12101899 1 Speedo Connector
12085485 1 Back up lamp connector.

This list came from here: http://www.salleechevrolet.com/Chevy...ons/gmt56.html

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'89 Formula - Thunderchicken - 355 Vette L98/T-56/3.45 9-bolt/black/t-tops - the fun car!
'90 GTA - The GTA - 5.0 LB9/TH700/3.27 9-bolt/black/t-tops/tan leather - the cruiser.