I was driving at 22mph in second gear and decided to floor it so it would down shift but instead it bucked hit the rev limiter and then shifted out of second. tried it again and same thing happens. It works fine if I go WOT from 1st but it doesn't downshift correctly when it's out of 1st. I'm leaning towards a tuning error since it doesn't happen from a dig. What do you guys think?

 

Mine acted wierd the other night when I floored it too. I was cruising at 45, stepped on it and it downshifted to second, held for second then downshifted to first then started pulling. We have the same tuner maybe its something to do with Allen.

 

00z71 has a 4l80e also and his does the same thing without allens tune So who knows what is happening.

 

Hahaha, the stock 4L70E in my 2007 Vortecmax does the exactly same thing. Annoys the **** out of me to get multiple downshifts when I just want to accelerate!

 

Maybe line pressure is too high and it's taking too long to exhaust the fluid. Do you guys know if your 4L80-E's have the waved plates in them? These kind of act like cushions to clutch engagement and disengagement to make the shifts smoother. On a downshift the pressure has to bleed off until the holding force can be overcome by torque. The more unnecessary pressure there is there the longer it will take for the pack to release. There's also sometimes an issue under high RPM where the fluid behind the clutch piston can actually be spun centrifugally outward under enough pressure to prolong disengagement. There are checkballs in the housings intended to let this fluid out. There really are a lot of things that could be going on here. The best advice I can give you on line pressure is to keep it as low as what's needed to maintain positive clutch pack holding without slippage plus a safety margin of about 10%. If you're going to tinker with line pressures you better have a scanner. Of all the different way we kill a transmission around here, nothing can do it swifter than bad programming....

 

my tahoe did it with a 4l60e but brian from pcm4less said a tune would fix it and guess what...it did!

 

Mine will shift like it is supposed to from a dead stop, but if i am doing 30-45 and I get on it, it will downshift to first but i will peg the rev limiter befoer it will shift to second or i have to let out just a little. If I am from a dead stop or I manually shift it to first, it will shift like it is supposed to. I have retuned my self and the problem is still there, but I will try to lower my shift pressure, maybe that will work ( never thought of it).
When mine first did this i thought it was my tranny, but now i feel better that i am not the only one ( maybe it is the way the 4l80 is desinged)

 

That happened to me once when i had my 80e, it was a little low on fluid. After i topped it off it never did it again.