4l80e swap

[Zacklee420]

So I just did a 4l80e swap in my 95 gmc (was a 4l60e that took a ****) everything is hooked up right but my rpms are way out, 2700/100kph the trans is out of a 97 so the input speed sensor behind the housing on the driver side isn't hooked up. I'm wondering if that sensor is causing the high rpms and shuddering when under load or if there's something else

 

[stutaeng]

Yes.

You need to repin the harness at the transmission connector, add/hookup the additional speed sensor and reflash your ECU for the correct transmission.

Not sure how you would reflash your ECU on your truck being a TBI...not familiar with TBIs. Someone else will know.

 

[Zacklee420]

Yes.

You need to repin the harness at the transmission connector, add/hookup the additional speed sensor and reflash your ECU for the correct transmission.

Not sure how you would reflash your ECU on your truck being a TBI...not familiar with TBIs. Someone else will know.

I have a new computer for this engine/trans combo both harness had green plug so i didn't think I'd need to re pin anything

 

[Supercharged111]

I have a new computer for this engine/trans combo both harness had green plug so i didn't think I'd need to re pin anything

You need to repin at the trans, not the PCM.

 

[df2x4]

As others mentioned, you definitely need to do some repinning. Scroll down on this page to the image that says "4L60E to 4L80E Wiring Conversion."

https://sites.google.com/site/sloppywiki/everything-ls/4l80e-info

That page is referencing newer LS PCMs so the input speed sensor wiring info is irrelevant to your application, but the transmission connector repinning still applies. If you don't want to mess with it there are a couple companies that sell adapter harnesses for the transmission connector, but they're expensive for what they are. I used one from Nelson Performance on my red truck.

To find which two PCM pins the input speed sensor needs to connect to, you'll need to look up the PCM pinouts for your truck. They can be found in the GM factory service manuals, which are available for download here.

https://www.gmt400.com/threads/88-98-service-manuals.43575/

 

[Zacklee420]

Everything works except I have no overdrive I've poured through forums trying to figure out why. It did come with a 3000-3400 stall converter but I don't see that preventing me from having overdrive

 

[Zacklee420]

You need to repin at the trans, not the PCM.

Both plugs were green the only pin I had to change was for the tcc solenoid but after I did that when I drove it the trans almost cooked