4l80e parameter question

[myburb]

6395/OE/4l80e has a parameter "PE line pressure vs input speed" and it has numbers between 1and 5 in the high torque rpm's. In the hac it looks to as though that is a straight psi increase, ie when in pe/wot it would add between 1 and 5 psi to what ever the governing tables were calling for. Is that the way it is? One step further if I added 5 to all the entries I would get 5 extra pounds line pressure than what normally would be applied?

[V8Astro]

I can't answer directly but there are similar tables in my 427/$31 system. I have successfully firmed shifts by adding numbers to the shift tables whose values are shown in "psi"

[myburb]

I have switched between $OE and $31 and pretty much feel they are the same so how much of a psi increase did you use to firm a shift? I also have plans to change converter loc and unloc to better fit in with our local speed limits.

[lionelhutz]

To me. it appears the 4L80e does line pressure very similar to the 4L60e. Neither have pressure feedback so in reality there is no way the PCM could meet a pressure demand directly.

I haven't tuned an 80e but the tables look a lot the same as a 60e so I'd say they do a similar thing. Best of what I could find says none of the line pressure values are actually line pressure. They are just factors used to look up the current for the force motor in the force motor tables. The pressure tables are all used to calculate a "line pressure". The maximum line pressure scalar then caps this value at the highest column to use in the force motor table (i've seen either 90 or 96 used here and don't change this one hoping for more line pressure). The line pressure is then looked-up in the force motor table to get the current to feed the force motor. A higher force motor current is less pressure and a lower force motor current is more pressure.

The table you listed would only affect the line pressure when in Power Enrichment mode. Is that what you're wanting to change? Yes, it would add line pressure but no adding 5 would no increase the line pressure by 5psi.

I suggest you put a line pressure gauge on the transmission before attempting to adjust line pressures. That way, you know the before vs after affect of your tuning vs guessing that it helped.

[myburb]

Thanks for the info on what is going on, ie pressure numbers scaled to electrical load on solenoid. Not knowing the actual sequence of events is why I have been reluctant to change numbers without knowing exactly what they do. It wouldn't take much of a mistake to harm a trans. The pressure added with pe was just one of the areas I was looking at. The actual interest is, the info I get on the internet is the 4l80e has a soft shift 2-3 and my motor puts out more torque than stock and being a towing rig it shifts full throttle at 4100 and I think a little firmer 3 engagement would be beneficial . I do have a dash mounted pressure gauge.

[96lt4c4]

Thanks for the info on what is going on, ie pressure numbers scaled to electrical load on solenoid. Not knowing the actual sequence of events is why I have been reluctant to change numbers without knowing exactly what they do. It wouldn't take much of a mistake to harm a trans. The pressure added with pe was just one of the areas I was looking at. The actual interest is, the info I get on the internet is the 4l80e has a soft shift 2-3 and my motor puts out more torque than stock and being a towing rig it shifts full throttle at 4100 and I think a little firmer 3 engagement would be beneficial . I do have a dash mounted pressure gauge.

look up the dual feed mod for the 400/4L80E. That will firm up your 2-3 shift. I did this to mine and my 2-3 is the firmest shift I have. I also removed the cushion spring in the direct clutch and added another steel and friction for a total of 6. If I had to do this over i would have left the cushion spring in and just do the dual feed mod. Mine shifts pretty hard sometimes.