Hi,
I'll start off by saying the car is a 2002 Nissan GU Patrol with a L77, 6L80E and seemingly the BCM to match from a 2015 VF series 2 SS V Holden Commodore. Its a 2.6+ ton 4WD, 33inch tyres with a 4.375 ratio diff. I believe the ECU is fed off the transfer case but could be wrong, the speedo was fixed when I used gear and tire wizard with my tire and diffs.
TL;DR: Should I put an equivilent vehicle's tune in the car and go from there? I saw a Sierra config file which seems to have the same tables as my TCM.
I've gone down the rabbit hole of trying to sort my trans out. It's been tuned twice. I've had the latest tune done by a shop in there for a while, 5ish years. Its had heating issues for the longest time. Multiple mechanics have told me the stock Patrol cooler is massive so external cooling doesn't seem to be the issue. After poking around the file and doing a bit of research, it seems the tune was running unlocked quite a lot. towing a 1.4t camp trailer on sand in unlocked 6th was enough to overheat the trans. The first tune in the car when I got the car was causing the wheels to skip when shifting in low gears at low speeds. I got it tuned and they fixed that, but I have a feeling the tune isn't suited for a large car. I've been tinkering with shift and lockup to mimic a silverado which seems to lock pretty early. I do like the way it drives now, but the shifts are aggressive.
Multiple downshifts are causing flare, single shifts up seem to be causing flare and downshifts are causing flare. Some shifts are definitely better than others. I've noticed that all my downshift pressures have the second row set to 2000. No idea what these rows represent, because my OS has the row headers as "???". I updated my 4-3 downshift pressure table to the below, moving 2000 to 1500 just to see how it would affect the downshift and it seems to have made a change.
kPa -40 -20 0 20 40 °C
??? 1000 1000 752 600 600
??? 1504 1504 1504 1504 1504
??? 1000 1000 1000 1000 1000
??? 1000 1000 752 504 504
Power 1704 1704 1704 1704 1704
But the more I look and compare against other tunes, the more i realise everything probably works together to make it shift properly. Should I just put in a stock tune and see how that goes? If yes, what tune would be good? Is a silverado or sierre better? Or should I stick with my current tune (attached). Also attached are logs from driving in stop start traffic and WOT. The car doesn't shift from 2nd to 3rd at WOT before hitting redline, hits redline then shifts, no idea why. I have reset the trans adapt and driven more than 200km. Also attached are some python plots of shift events.
Any guidance is greatly appreciated. It seems to be near impossible to get a straight answer/guidance. My neighbour has a very similar set up to me, and his tune is different again which makes things even more confusing. Happy to provide that as a reference if anyone thinks that'd be helpful.