ECU swap when changing from 700R4 to 4L80e

[Dezertracer]

Does anyone have experience swapping a 350 TBI/4L80e ECU and wire harness (91 Suburban 2500) into a 350 TBI/700R4 (89 Blazer) with a 4L80e transmission swap? Seems like a cost-effective alternative to a standalone controller for the electronically shifted transmission.

What is a good source for the schematics and ECU pinouts on a 91 Suburban 2500 ECU?

The mechanical to electric speedo conversion will be an additional issue.

 

[Chevman88]

I'm going through something similar (th400 to 4l80e) and I ended up just getting the TCI standalone controller. Keep your existing ecu for the engine and you'll need to splice a few wires for the standalone.

Problem with trying to use factory is that you'll run into compatibility issues through the various iterations of 4l80e unless you get the harness, ecu/tcm, and transmission from the same vehicle.

 

[sweetk30]

if you have both vehicles just swap the whole harness over no splicing or rework needed for electric speedo .

and search the archives here injection section for eagle mark write ups . he was a GOD at this stuff ........ r.i.p. brother

 

[imiceman44]

Does anyone have experience swapping a 350 TBI/4L80e ECU and wire harness (91 Suburban 2500) into a 350 TBI/700R4 (89 Blazer) with a 4L80e transmission swap? Seems like a cost-effective alternative to a standalone controller for the electronically shifted transmission.

What is a good source for the schematics and ECU pinouts on a 91 Suburban 2500 ECU?

The mechanical to electric speedo conversion will be an additional issue.

If you have the complete harness that came with the 4l80e I would use that.

 

[Wes Harden]

There was a wiring update mid-late 90's for the 4l80e.