6L80 won?t stay in 6th

[DG370]

Hi all!

Hoping someone has some prior experience of this, from my searching it appears the 6L80 is output shaft speed limited or something?

The problem I?m having on my off roader is (seemingly) regardless of what values I put in the ?shift scheduling? tables it will either shift down from 6th to 5th, or block me from going into 6th at all.

Obviously running on reduction box so trans VSS and road speed are irrelevant to each other.

Just a note this is running standalone via a TCM2600.
Everything else is peachy.

TIA

[hjtrbo]

Presuming its at close to or at WOT it won't go in or shifts back? If yes, preventing that is something we haven't got access to. Happens on 6L90 as well.

[DG370]

Hi, actually no, looking at the logs it?s as soon as it hits 230kmh in 6th it drops to 5th regardless, most annoying

Is this something that ?safety shifts? will address?

[hjtrbo]

Ah ok. Speed limit it is. It is annoying. I gave up looking for a fix. I didn't try safety shifts though.

[DG370]

Thanks, it?s a bummer! Pointless having 6 gears if you can?t use them!

There must be a way around, anyone else?

[DG370]

Anyone got a solution?

[DG370]

To help anyone else out, Zero Gravity said;
It is hard coded to protect one of the hard parts. You are limited to around 4000 rpms in 6th gear

[Tre-Cool]

if i get time over weekend, i might run 1 of my cars up on the hoist and see what vss, input, output shaft speed it changes down. Then see if i can find that value in the bin file of the trans.

I'm not 100% it's a vss speed, from previous logs it was around 220kph that it dropped from 6th back to 5th for me in cars.

[DG370]

Hello, that would be greatly appreciated, same for me on the logs it looks to be 230K, transmission speed not vehicle actual.

[hjtrbo]

What else can you do with the binary? I presume you've got checksum figured out. Definition file? And flashing method. I'm interested...

[Tre-Cool]

What else can you do with the binary? I presume you've got checksum figured out. Definition file? And flashing method. I'm interested...

you just need to know the address in hex, then in my case define the settings to convert decimal value to values that make sense via multiplier/factor. I'm doing this in efilive, but it's the same deal with HPT's User defined parameters.

t43-tapshift.PNG

raw bin is in hex values, convert that to decimal, then multiply it by 0.0078125 for kph.

it seems all the raw speed tables start with a 00 11 which converts to 17 in decimal. coincidently there are 17 hex pairs that follow based on pedal position for the corresponding speed value.
"0.00,6.25,12.50,18.75,25.00,31.25,37.50,43.75,50. 00,56.25,62.50,68.75,75.00,81.25,87.25,93.75,100.0 0"

[hjtrbo]

Nice.

Is efi fixing the checksum when you make a change?

Do the addresses generally change for the same parameters across different operating systems?

I imagine it'll be a needle and a haystack to find the right scalar to change without a definition. Do you know if 1 exists out in the wild?

[Tre-Cool]

yes efi or hpt will fix the checksum as part of the segment calculation.

address location is different for nearly every calibration, but generally once you know the hex value from 1, you can search for that in another file. typically these values don't get changed as they kept the same limits across multiple os/cal's.

for now im doing os/cal 24256025/24254908 because i have 2 cars that use it, but have different gearing. so it will be interesting to see when i log them what speed & TOSS they downshift back to 5th.

[hjtrbo]

I do have a couple of T43 bins here but no definition file. I do have addresses for Aussie LSA E67 PCM's that I use with user defined parameters to get HP up on par with the extra E85 and emissions tables EFI has. But never dived into the T43. I can get bins easy enough so can always change something in the tune and see where it is located pretty quickly. But to find the 6th lockout scalar would take way to much analysing to even guess where it is.

[Tre-Cool]

ok. so just tested. both cars down changed at different vss speeds which was expected as i didn't think it was a vss speed that made them do it. however the input shaft speed of 3757 is where they both match! & then downshifted.

So that's the beginning clue.

I just need to find the rpm conversion factor as i've lost some info that i had this noted down in.

edit, might be 0.19531

[hjtrbo]

Fuck man, nice work bro, respect! The vss tables for shifting, what byte size were they? 3757 is a very unique number. Thanks for posting, that's a MASSIVE clue. A weekend of searching awaits 🤙

[hjtrbo]

I suppose, the obvious question, for the guys with higher powered cars that can push north of 300km/h... What's at risk of spinning to fast and exploding apart if we bypass the lockout scalar???

[Tre-Cool]

I suppose, the obvious question, for the guys with higher powered cars that can push north of 300km/h... What's at risk of spinning to fast and exploding apart if we bypass the lockout scalar???

3757 was the input shaft rpm they downshifted. so we might need the factor to convert that into a hex value, then hope that we can find it. If it's just 1 value, just gotta hope there isn't other tables or limits using the same value.

I'm one of those high hp guys, basically make changes at your own risk. if shit explodes, diddums.

Pics below are from same trans os/cal
Car 1 - 3.07 diff gear
t43-vy-downshift.PNG
Car 2 -3.23 diff gear
t43-ve-downshift.PNG

Just looking through logs for both closer, there is logged data going over the 3757 value to say 3760, then next cell 3753,3757 then the downshift, but i think that's essentially the min value it needs to see as rpm is bouncing a touch.

[hjtrbo]

Excellent. The search begins.

I was a bit pissed off I couldn't get to 300. Hit the limiter at 298 in 5th. Fucken spewing. Haven't been there again since. Street tuners can't get a proper run in, pftttt, hold my beer lol.

[DG370]

Nice work TreCool, that tally?s with my logs input shaft rpm.

The reason they put this safety factor in is because 6th is such a tall overdrive it puts tremendous stress on the 456 shaft, now if you have an upgraded shaft your good to go?