BigKID

iTrader: (5)

First off this is a 4L80 conversion, EC_Tune did the segment swap and his instructions were followed perfectly to load it in the PCM. The trans is a stock low mile '05 with a Transgo HD2 shiftkit. It shifts perfectly at part throttle and fluid level is good. At WOT it just will not up-shift. I originally thought it was the input shaft speed sensor connection at the PCM as I had no input shaft rpm when logging. After redoing the connections and getting good rpm on the pid the problem still remains. It will not shift 1-2 or 2-3 at wot. I have attached my current file and a log showing a missed 1-2 shift as it bounced off the rev limiter at 6400. The screen shot is showing where it 'should' have shifted according to the 6000 rpm / 50 mph commanded shift point in the tune.


Is there a pid in the scanner for 'commanded gear' to see if it is a tune or mechanical problem?

Wilde Racing

iTrader: (26)

I know EC_Tune knows his ****, but I have never had good luck with a seg swap. I say start with a 2500 (lq4/4l80e) tune and swap the engine peramiters. It would be the easiest thing to try.
BUT the fact it shifts at light throttle kinda proves the tune is o.k in that aspect....

BlackGMC

iTrader: (31)

I would substract 5-7mph off the entire Full Throttle Shift Speed table.... You have the MPH to close to the actual shift point.....

BigKID

iTrader: (5)

I was thinking the same but figured since it is beyond the commanded mph it should shift especially after 400 rpm and 5 mph. Maybe the PCM is too slow or I am reaching that point too quickly. I will try lowering it and see if that works.

thunder550

iTrader: (70)

I had to drop my commanded shift RPM and speed way down to get it to shift where I want. Example: To get it to shift at 5700 RPM/55 mph I think I had to se it to 5000 RPM and something like 47 mph. Try dropping both RPM and speed way down and see if it will shift.

zippy

That seems to be a common problem even on some of the 65E's one you get into the higher hp levels. The 80E I've found to have this problem more often though, especially in boosted applications. I also agree with the segment swap issue, I'd just start with a stock O.S. for a 4L80E.

carfreak07

iTrader: (10)

I just done a 4.10 gear in my truck and now it often hits the rev limiter before shifting....it never done that before with the 3.42 gear. Is this the same problem as the op? I only have a level 3 4l60 but am making some decent hp. Any advice other than the above mentioned?

zippy

That's likely just a mph to rpm shift calibration issue. That is fairly normal.

BigKID

iTrader: (5)

Got it figured out thanks to Bill @ HPT. It is related to the mph you guys were suggesting but is a little more indepth and explains why some of you guys are having to put the lower mph for it to work. It has to do with the calculated Trans Output Speed which is different from the vehicle speed and is the mph the trans and tcc tables are based on. Check out the thread on HPT forum for the full scoop. http://www.hptuners.com/forum/showthread.php?t=19263

BlackGMC

iTrader: (31)

very interesting find!!!! gonna have to bookmark this thread!! Thanks for the research...