4l80e swapped, no 4th gear

[Zacklee420]

Blew the 4l60e in my 95 so I've put a 4l80e from a 97 in. I have repinned everything correctly and wired in the iss but thats where things get wierd, with it hooked up I get codes 68 and 85 when I unplug it those go away but code 74 shows up naturally. Also for some reason with the tcc solenoid wired into the computer it slips all the time but if I wire it to a switch to manually control lockup I have no issues. No matter what I do I cant get 4th its like it doesn't exist. Has anyone else encountered this issue?

 

[Supercharged111]

Did you flash it for a 4L80 or get a replacement PCM?

 

[1997]

95 was a 1 year only .... thinking you may need to re-check your wiring since you're using a 97.

 

[stutaeng]

4l80e swap

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...

www.gmt400.com

 

[Zacklee420]

Did you flash it for a 4L80 or get a replacement PCM?

I got a pcm for the 4l80e

 

[Zacklee420]

95 was a 1 year only .... thinking you may need to re-check your wiring since you're using a 97.

Its been checked re checked and checked again by someone else

 

[Supercharged111]

Did you install a known good transmission?

 

[Zacklee420]

Did you install a known good transmission?

Yes, I know the previous owner of the truck it was good. After swapping the chip into my old computer and putting it in the only code is 68- engine speed and trans input speed not matching

 

[df2x4]

This really sounds like a wiring or tuning issue. I know you said the wiring has been double and triple checked, but are you 100% positive that the ISS is wired to the correct two pins at the PCM and you've moved the correct pins/wires in the transmission connector? The factory service manuals have PCM pinouts for each engine type, are you sure you were looking at the right one?

 

[BeXtreme]

Are ISS and OSS switched?