Preventing Upshift

[shaodome]

Perhaps this is a misunderstanding of the logic or I didn't see it in the docs....

When tuning the car on the dyno, I would like to just hold the car in 3rd gear for the full pull. Letting off the throttle at the end of the pull resulted in the car shifting to 4th due to the shift table layout even though the car was in 3rd and registered 3rd as the manual gear gauge. I would have thought it would have prevented an upshift?

As a workaround, I just adjusted the shift table for dyno use, but I was just surprised a little by the behavior. Lance my MSQ can be found in that 500psi sensor thread.

We lifted the head on Saturday near 1000hp (stanard ARP bolts are a NO NO!), so you can see the coolant explosion, which is kinda funny, but in the video you can hear the car shift to 4th right before the geyser. I hope to have it back together in a few days (just waiting on the head to come back as it was a little torched).

https://www.youtube.com/watch?v=0XqwHKAInZs

[Bernard Fife]

the car shifting to 4th due to the shift table layout even though the car was in 3rd and registered 3rd as the manual gear gauge. I would have thought it would have prevented an upshift?

Shaodome,

If rev limit checking is on, it can force a shift despite the auto gear table. A manual shift using the shift buttons can do it as well (even if inadvertent). However, if you have a log and datalog of the unexpected shift, I can check these against the code to see if there are code issues.

Lance.

[shaodome]

Rev limit checking was disabled for the dyno.

I do have a log of which I can post it tonight and the shift buttons were not connected.

Was I correct in my logic? If I put the shifter into 3rd gear, should it NOT go into 4th, even in auto mode given provided rev limit checking was off.

What I really am asking is, if the ECU is set into auto mode and I put the shifter into 3rd gear instead of 4th, does the ECU still follow the shift table when it comes across 4th gear in the able, despite shifter position?

The docs mention a switch for manual mode, but that then requires the shift up/down buttons to be wired as well, right?

[Bernard Fife]

does the ECU still follow the shift table when it comes across 4th gear in the able, despite shifter position?

shaodome,

It is not supposed to. The manual gear lever position is supposed to be the highest gear that will be selected in either auto mode or manual mode.

If the buttons are not wired, they should be pulled high with a 5V pull-up circuit (basically a resistor tied to a 5V source). Otherwise they are floating and could possibly trigger a shift in some situations. If you built the shift button circuits as for a 4L60e, but didn't connect a buttons externally, you should be fine.

A datalog will show several interesting things about this (switch states, target gears, manual gear position and much more).

Lance.

[shaodome]

OK you can see the issue in the first part of the log. Honestly, in the frenzy that the dyno was I MAY have had it in 4th :0/

That being said, the VSS looks like heck. It's very choppy at high speed. Suggestions to look at here? It's a 4L80e

[gui67]

Hello Shaodome,
I also have a 4L80e, I had problems with the OS and IS speed at the beginning, but not as bas as you have.
I ended using the dual VR board from Jean to get the right speed. Andrew did the same on his Ford transmission. Now it is OK.
I put the board in the MSGPIO casing, using unused pins from the AMPseal connector, and shielded cable to the OS sensor

[shaodome]

Hello Shaodome,
I also have a 4L80e, I had problems with the OS and IS speed at the beginning, but not as bas as you have.
I ended using the dual VR board from Jean to get the right speed. Andrew did the same on his Ford transmission. Now it is OK.
I put the board in the MSGPIO casing, using unused pins from the AMPseal connector, and shielded cable to the OS sensor

Hi Gui!

I read your thread somewhere just recently (maybe it was on Jean's site?) I sent Jean an e-mail about the boards, but he is apparently moving, so I have yet to heard back from him.

In dealing with the MS3Pro I've become familiar in dealing with VR noise and I'm wondering if installing a shunt would be helpful here. I'll give it a shot next time I'm on the dyno. I also noticed in my MSQ that the VSS masking is currently set to 0, which means NO filtering is being applied.

[Bernard Fife]

in the frenzy that the dyno was I MAY have had it in 4th :0/

shaodome,

You are probably correct, as I don't see any point in that log where the currently selected gear (cGear) exceeds the manual gear lever position (mGear).

Lance.