Quote:
Originally Posted by gumby79
Without doing the research on your specific transmission no one can answer the questions about your specific unit. You're 7000 miles and no issues showing up sounds like the trial-and-error method has shown you to be on the right track. I gave the examples of my Allison Transmission because it has both configurations available torq converter locked and unlocked shifting
GM Chevy use the unlocked+pressure control. Medium-duty Freightliner Mercedes and other such medium and heavy-duty manufacturers use a locked shift pattern from 2nd gear through 6th Gear by controlling line pressure, engagement, and release rates on three separate solenoids to adjust shift firmness, and prevent RPM flares AKA slipping the clutchs
Bottom line If your transmission is anything like mine, not being able to control the line pressure + locked shifting may be problematic trial and error will rule that out by surviving thousands of miles, or confirm that it is a problem by wetting the bed in short order. You reported no additional abrasiveness to the shifts having bypass the pressure control and manually locking the torque converter and that it is a very small sample size. Get a bigger a sample, then report back. Blackstone fluid analysis is about 20 bucks if it's wet they can test it. Cheap insurance and a way to test it without making it fully wet the bed
I apologize I evidently came off negative. I do not have experience with your unit I do however have experience with medium light-duty applications. As far as your experiment has been explained sounds like you're on the right track and things are looking good. And it sounds like it's time to move on to phase two of testing locked + no pressure control. I would run the experiment the other direction however locked with pressure control monitoring the tcm's pressure readings to see if it is adjusting to compensate for a locked shift then run a phase 3 disabling bypassing the pressure control system
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Thank you for all the info, I really appreciate it. I tried researching how this trans controls operates and controls pressures, but try finding info on how Honda BMXA/SLXA transmissions operate. It's not easy, there isn't much info out there.
I am feeling pretty good about not having pressure control after 7K trouble free miles, fluid still clean, and a seemingly healthy trans. I haven't felt any slipping, slow shifts, or anything else disturbing, so that's probably a good sign too. I feel like if something terrible was going to happen it would have by now.
The problem with letting it shift locked with pressure control is that the PCM apparently keeps the pressure to the TCC low enough that the it either won't apply or will only apply partially (slips) under certain conditions (like when stopped, in 1st gear, shifter in D3 or 2, under load, etc), so I have to keep the pressure control solenoids disabled for my manual lockup to function correctly. Although maybe 1 of the solenoids is to control the TCC pressure and the other is to control pressure during shifts. I'm not sure, I'd have to try disabling one solenoid at a time. My trans doesn't have pressure sensors, so I can't monitor the pressures.
As I said this is my only functional car at the moment and I am afraid of doing damage and being without a functional car if I ruin the trans in this one, so I am likely not going to make a habit of shifting with a locked converter until I get at least 1 of my other 2 cars running so I have something to drive while I fix this one if I break it.