I'm kind of at a loss with this one. I recently rebuilt my 4L80e with all the usual mods (build list with all clearances at end of post and also in my build thread in post #73) and during my test drives, it would not engage 2nd gear with the shift lever in manual 3rd or OD. In manual 2nd, it would upshift and downshift no problem but upon moving the shift lever to manual 3rd or OD, it would downshift to 1st until the set 2-3 shift point when it would then upshift to 3rd gear. 3rd and 4th work perfectly with no slip and lockup worked flawlessly as well. I checked with HP Tuners VCM scanner that I could command both A and B shift solenoids independently, and I also tried using the scanner to command 2nd gear - same story. I could command the 1-2 shift with the lever in manual 2nd, but not in manual 3rd or OD.

I figured that I either assembled the intermediate sprag wrong or I somehow blew it up on my initial test drive, so I dropped the trans and opened it up. Slight amount of clutch material in the pan, but no glitter, metal shavings, chunks, etc. Filter still looks new. I put about 20miles on it since the rebuild. I have the trans tore down to the center support / intermediate clutches and everything looks brand new still. I also verified the intermediate sprag rotates the correct direction - free-wheels clockwise and locks counter clockwise. The band surface on the drum looks mint still and the band shows little to no wear too. I'm at a loss as to what could be causing my trans to not shift into 2nd gear unless the lever is in manual 2nd. I would think if it was a solenoid problem, it wouldn't shift to 4th with both A and B solenoids needing to be ON for 4th gear, but I could be wrong since I'm no transmission expert. I'm using a factory 0411 PCM (2002 LQ4 & 4L80e in the original file) to run my 6L and 4L80e.

Here are my build specs:

rear section endplay: 0.007"
front section endplay with rear loaded: 0.005"
front section endplay with rear not loaded: 0.012"
output shaft endplay: 0.005"

direct clutch clearance: 0.040"
forward clutch clearance: 0.055"
over-run clutch clearance: 0.025"

More info on the build for future reference:
no wave plates anywhere
internal dual feed mod
accumulator delete (CK performance)
CK Performance pump
bleed hole in direct clutch housing (to eliminate clutch soft apply at high rpm)
new bushings and seals everywhere
6 clutch direct

 

Figured out my transmission issue. I tore it down to the center support and did some investigation into the problem. I was expecting to find my intermediate sprag completely toasted and/or assembled backwards, but it looked just as good as when I assembled it a few months ago and the drum surface where the intermediate band rides looked brand new too. Sprag was assembled correctly, locked counter clockwise and free wheeled clockwise. I tried to overpower the sprag on the bench and I could not do it by hand. Digging deeper since I was at a loss, I decided to check the clearance on my intermediate clutches. It measured out to be just about 0.095" which is looser than I'd like, but "technically within spec of 0.040-0.123" Upon disassembly, I found I omitted the factory wave plate with legs which measured in at 0.045". Adding this back in brought my clearance down to 0.050" which is right on nominal for the 0.040-0.060" clearance I was shooting for.


Direct drum band surface:


Intermediate Band:


Intermediate clutches and steels. Here you can see some wear patterns from where it looks like the clutches were slipping on the steels. Nothing was hot spotted or worn down though.


And finally, the culprit. Oops:


Root cause analysis complete - my no 2nd gear was my own doing. I left out the seals on the intermediate piston. At first when I was doing my air-check on the intermediate clutch, I thought it was just a cut seal since I was seeing bubbles at the inner seal and outer seal areas. No big deal, a $3 and $4 seal. Pulled it apart and found there was no seal in either location! Apparently my air-checks upon initial build up were not thorough enough. I assembled the center support for mockup, and then never disassembled it to install the seals. Lesson learned. Good news is that I still had my overhaul kit and the two seals were sitting right in there. Installed and air checked on the bench, piston travels up and down now like it should.

Here is a video of the air bubbles I was seeing during my aircheck:

You Tube