I have completed my 6.5/4l80E swap into the scout. I still have one problem though. My 4L80E slips badly but it seems to shift. I have an autoenginuity GM enhanced scanner reading with no codes reported. The trans is a 1997 from LKQ. i will be calling monday to see if they will honor the 6 month warantee.
Does it sound possible to have it slip badly and throw no codes?
The setup is a 1996 and is OBDII. I first thought it was low on atf till i drained it from the pan then put 5 quarts in. the dipstick reads full when in park.
I do have one possible suspect but am not familiar enough with the 4l80E to know if my suspicions could be the cause. When i plumbed the trans cooler i used hydralic hose fit to 1/4 pipe, but on the rear fitting on the trans the old line fitting had a nipple extending about an inch into the trans and my fitting was just pipe thread. could that be my problem...? http://www.dieselplace.com/forum/images/smilies/help.gif

Do you have a TPS (throttle position sensor) on that vehicle? My tranny was having similar issues and had no codes (that were defineable) and changed out my TPS and the problems went away. I'm not sure how it works on a swap out with different wiring etc, but may be the cause.
Hope this helps,
Mark

It is possible to slip without setting a code. The tests for the slip codes only run in 4th gear TCC applied.