Can someone help me with these questions I have?

[MrOverCast]

Okay so I have a 5.7 L31 vortec engine laying around with the wiring harness on it. I 4011 swapped the black box PCM thats was originally on the harness. I want to put the engine and harness in my 1985 chevy C20 pick up but i don't know if some things will work without them. here are my questions

Does the PCM need a speedometer signal to run properly
or a tachometer signal.
will the transmission shift into park drive etc with the mechanical shifter thats on my truck or do i need some sort of electric shifter

 

[yevgenievich]

As long as sensors in place, no speedo or tach in cluster needed. Shifter might be an issue with mechanical vs cable attachment if the one on newer trans is set up for cable. But not hard to adapt.

 

[MrOverCast]

As long as sensors in place, no speedo or tach in cluster needed. Shifter might be an issue with mechanical vs cable attachment if the one on newer trans is set up for cable. But not hard to adapt.

im looking to use a 4L80E

 

[yevgenievich]

im looking to use a 4L80E

Newer 4l80e used cable shifter, older was a rod. 91-93 4l80e valve body goes with 91-93 ecu. Also differences in cooler lines and number of speed sensors if 4x4 trans amongst other things depending on year.

 

[MrOverCast]

Newer 4l80e used cable shifter, older was a rod. 91-93 4l80e valve body goes with 91-93 ecu. Also differences in cooler lines and number of speed sensors if 4x4 trans amongst other things depending on year.

the wiring harness thats on the 5.7 vortec has 2 speed sensors. so basically i would have to find a older 4L80E that has 2 speed sensors and a rod shifter? i have a L31 2001 chevy express van tune file on my 0411. would that work or do i have to find a tune file for the 4L80E's valve body

 

[stutaeng]

I bought a '95 4L80e from a C2500 ECLB. It had the short shift shaft, and I think those earlier GMT 400 trucks had the neutral safety switch on the steering column? Anyway, mine was going on a newer truck with the neutral safety switch on the transmission.

I had to change the short shift shaft to a long one to work in my case. You should be able to do the opposite. IIRC, the short shaft is the same as the TH400.

I know the early 4L80s were a little different, but I've never messed with the '91-'94 models. I'm assuming your truck is TBI?

All 4L80s have 2 speed sensors. The very early ones (91-92?) had a bolt-on wire connector. I've never seen what that looks like though.

 

[yevgenievich]

the wiring harness thats on the 5.7 vortec has 2 speed sensors. so basically i would have to find a older 4L80E that has 2 speed sensors and a rod shifter? i have a L31 2001 chevy express van tune file on my 0411. would that work or do i have to find a tune file for the 4L80E's valve body

With vortec and 411 ecu, 94-99 4l80e would probably be preferred. 91-93 units would need newer valve body to operate correctly on 411 ecu. Early 4x4 4l80e used two sensors, while later 4x4 units had one, while using one from tcase for second sensor. Otherwise 2wd units have two sensors. Get correct coolant line if using 97+ 4l80e. Might have to replace the shift rod or adapt cable to the column shifter.

 

[MrOverCast]

I bought a '95 4L80e from a C2500 ECLB. It had the short shift shaft, and I think those earlier GMT 400 trucks had the neutral safety switch on the steering column? Anyway, mine was going on a newer truck with the neutral safety switch on the transmission.

I had to change the short shift shaft to a long one to work in my case. You should be able to do the opposite. IIRC, the short shaft is the same as the TH400.

I know the early 4L80s were a little different, but I've never messed with the '91-'94 models. I'm assuming your truck is TBI?

All 4L80s have 2 speed sensors. The very early ones (91-92?) had a bolt-on wire connector. I've never seen what that looks like though.

The engine and transmission is going into my 1985 C20 that has a stock carbureted 350 with a 700R4. id have to look in to the short shaft and long shaft.

 

[MrOverCast]

With vortec and 411 ecu, 94-99 4l80e would probably be preferred. 91-93 units would need newer valve body to operate correctly on 411 ecu. Early 4x4 4l80e used two sensors, while later 4x4 units had one, while using one from tcase for second sensor. Otherwise 2wd units have two sensors. Get correct coolant line if using 97+ 4l80e. Might have to replace the shift rod or adapt cable to the column shifter.

Oh okay that makes sense. But i don't have a transfer case. for all 4L80E's is one sensor for the drive shaft and the other for the transfer case? if i red that correctly?

 

[yevgenievich]

Oh okay that makes sense. But i don't have a transfer case. for all 4L80E's is one sensor for the drive shaft and the other for the transfer case? if i red that correctly?

There are input and output speed sensors for all 4l80e. Eventually on 4x4 applications gm started using the sensor on transfer case for output. On a 91 4x4 truck, there are three sensors: trans input, trans output, tcase output. The shifter shaft location on a 4l80e also does not line up exactly in the same spot as 700r4. Not sure if will be an issue or not, as the shift linkage is frame mounted on squares. I don't remember from my 91 factory 4l80e square if linkage was slightly different or not.