Curious about Allison 6 speed solenoid logging

[Brian1]

I was playing around with stand-alone logging to answer someone elses post in another forum site. But I setup a BBL and selected only the TCM AL6 for my Allison 6 speed. I had selected the shift solenoids but they do not show correct for the gear selected. I figure since there was 5 of them they refer to the 5 clutch packs. only the first 3 show any activity and some gears show the same ones.

I selected the PCS1CP, PCS2CP, PCS3CP, PCS4CP, PCS5CP. But only first 3 show anything on them. I will add a log showing those pids and the gear the Allison is in at the time.

So from what I know the following clutch pack combo produces the following gear. Is the following correct?
1st C1 C5
2nd C1 C4
3rd C1 C3
4th C1 C2
5th C2 C3
6th C2 C4
reverse C3 C5


I currently running
V7.5.6 build 99
V8.1.2 build 75
firmware and bootblock fully updated from those versions.

Thanks for the info and to whether the AL6.pmm is correct.
Brian

[Cougar281]

The Pressure Control Switches (PCSxCP) are not the solonoids; they are the switches that confirm to the TCM that the solonoids and valves are doing what they're supposed to. You'd want to log TSTATE03 to see if the solonoids are on or off. There are only three solonoids; the clutch combination is achived through the VB and the shift valves.

[Brian1]

Ok I see know. I did not tear into my Allison for the rebuild and should buy the ATSG Allison book one of these days. But I see what your saying.

Thanks for the info.
Brian

[Cougar281]

The other thing about those PIDs is their supposed to be "Commanded Pressure" PIDs, but unlike a Ford 4R70W or possibly GM's 4L80E and similar (not sure about the GM transmissions), the pressure isn't electronically controlled in the Allison; It's controlled mechanically in the front pump assembly, hence shimming the spring to increase the pressure, so why there are any "commanded pressure" PIDs is beyond me... The TCM has no way to read pressure other than "On" or "Off" via the switches in the PSM, and no way to control the pressure other than commanding x% duty cycle on the solonoids that are not binary On/Off. Any pressure readings from the TCM are likely "guesses" made by the TCM based on what it "thinks" the pressure is coming out of the pump and the duty cycle of the solonoid in question.