S4 t2 engine, transmission, wire harness and ecu into a S5 NA shell?
 

How hard is it to put the full drive train and ecu and harness from a s4 t2 into a s5 NA shell?

my t2 was in a hit and run and now has frame damage but I found a clean s5 shell and wonder if I can swap everything over

If you do it the right way I would say about a month as you will run into little snags. It can be done in a week if you are technically strong and have proper tools. The whole rear sub frame can be taken out and that will resolve the T2 axle and diff swap. The dash harness and engine harness both enter the ECU; however the S5 and S4 have different harnesses. The other issues is moving and removing components that have not moved in years baking in heat. expect connectors to crumble, vacuum lines to break, and bolts to snap.

Everything should be fine on my t2 as it has been generally maintained. I'm concerned with the compatibility of the harness to the ecu. The physical moving of parts should go fine.

I know the dash harness goes into the ecu but I'm not really sure what they control. How do people get around this issue if they get an aftermarket ecu like a haltec?

the wiring harnesses conectors between everything are not compatible, so you would most likely have to do a lot of splicing, to mate the s5 body harness, to the s4 engine harness, and s4 ecu. it is doable, but you would want to be well versed in reading wiring diagrams, to compare things, to make it run.

Not terribly hard IMHO, but extremely time consuming, and you'll need to be very comfortable interpreting the FSM wiring diagrams for both S4 and S5 versions so you can pull off all the little S4/S5 integration details with the dash & HVAC/ancillary components. Since you still have the entire S4T2 drive train, ECU & all wiring harnesses going to your S4T2 ECU, you have all of the critical components you'll need. Basically you'll need to move all 3x ECU wiring harnesses (i.e., follow the 3 plugs that connect to your S4 ECU) from your S4T2 over to the S5 shell, then deal with a few differences where the S4 ECU harnesses connect to the "dash" & "body" harnesses. Off the top of my head I don't recall all the differences, but it's limited to things like gauges (tach, boost, coolant), idiot lights & HVAC connections. Since you have an entire S4T2 to scavenge from, it may even make sense to port over the entire S4 dash cluster, idiot light cluster, HVAC controls and associated wiring harnesses into the S5 shell.

Yep, either this or run a s5 engine harness, ECU, and OMP. I'd say the S5 harness is the easiest version

*I would have suggested that, but the OP said his wrecked shell (with the good drive train/ECU) was an S4T2, that he wants to transplant into an S5 NA shell - since NA, I assumed he didn't have an S5 T2 ECU or any of the S5T2 ECU wiring harnesses to play with.

I was wondering how complete this S5 that it's going into is. Easiest if it's a complete car is to get a S5 TII ECU to run it with and the just swap the TII drivetrain. The N/A wiring harness could be used by shortening lengthening the necessary wires. Below are the only differences I'm aware of beside length between the S5 harnesses.

Pin-----N/A-------------------------------------------Turbo
1U---AT Switch---------------------------------Mileage sensor no.2

2M---Solenoid Valve----------------------------Knock Sensor
------(Variable Dynamic
------Effect intake control)

3N----EC-AT Control Unit-----------------------Not Used

3R----6-port induction--------------------------Duty solenoid valve
-------system-----------------------------------(Turbo boost control)

You also may have to come up with a knock sensor since IIRC the S4 didn't have one, and of course the S5 ECU goes into limp mode without the OMP so you'd need that even if just tied off to the side.