Hi my name is John Troxell I have a 1999 Sierra Sleeper with a nasty LQ9 I just recently rebuilt the 4L60E for the 2nd time in 2 months. The first time i did after 500 ml of easy break in i gave it some gas and 3rd gear jumped the rpm's to 5grand. Took it apart again and the capsule with checkball was leaking. Just got it back in grumpy truck yesterday and no slipping but its shifing funny 1st and 2nd . Should i have the pcm re programed? or do i go ahead and take it through a drive cycle and see if it re learns? Will downshifting where i want it to help the computer know how I drive? It seems to drive manually ok but in OD funny. PLEASE HELP!!!!

 

Your 4l60 will only get worse until you do an upgraded rebuild. BTW, the '99 computers can be a little quirky on the trucks. The PCM's are OK, but the BCM's are a little off. Back on topic, the symptoms your transmission have are related to burnt/worn clutches, and no amount of computer trickery will fix hard parts. A good rebuild with 5 pinion planetary gears, a beast sun shell, z pack clutches, and a good TC should make it hold whatever N/A power you throw at it. However, after that is done invest in a trans cooler to keep from burning it up. Also, these transmissions aren't controlled by a learning computer. All shift points, pressure, etc, are pre-programmed.

 

Correct, there is no learning on the trans side. Im not sure if your implying that your trans tune is stock but imo it shouldn't be. Even stock transmissions benefit from good tunes. That would be one of the first things I did. If that's done correctly you can use that tune in a stock or built trans without issue, so it won't matter what trans you are actually running. I can email you a tune to use if you have someone that can upload it with hptuners.

 

The first step in any trans diagnosis is to connect a pressure gauge and monitor it while driving around and letting the trans shift. Posting various pressure values will give us a lot of info.

BTW - I'm not aware of a single sponsor or pro builder still using Z-pack clutches; they might hold 350HP, but not much more. Everyone is now using the BW Hi-Energy or Raybestoz GPZ. Definitely don't use Alt-Red in the 3/4 clutch although they are OK for other clutches.

 

Im currently running the zpack in the camaro but my most current trans in my Yukon the builder told me he has changed to something different.