Shifting with torque converter locked
 

Hello everyone, I am wondering if it is bad for my 2005 Honda Civic’s transmission to shift with the torque converter locked up. With my solenoid mods to raise line pressure, it shifts somewhat hard when locked up and I am wondering if this is bad on it. I like hard shifts, but I certainly don’t want to destroy my new (to me) transmission by shifting it with a locked torque converter. I don’t allow it to shift while the converter is locked up because I am unsure of the long term effects of doing do.

Also, I modified my pressure control solenoids so the trans runs at a higher line pressure so it shifts quicker and so the TCC instantly fully applies whenever I want it to. What I did is I unplugged the pressure control solenoids and plugged in extra solenoids so it doesn’t set a code and go into limp mode. I have been running it for about 6K miles this way and nothing bad has happened yet that I can tell, but I am wondering if shifting with high line pressure is bad for the trans in the long run.

The trans does not shift excessively hard (by my standards) from the solenoid modifications, so I would expect that this modification could actually extend the life of my trans because it shifts quicker, meaning the clutches engage faster and slip for a shorter amount of time, but I don’t know a lot about automatic transmissions, so I may be missing something.

Thank you very much in advance, I really appreciate your help.

Traditionally, in a powerglide used for racing, no TC, the bands tend to wear out faster, particularly the low one used to get the car moving.

Notice the caveats.
The secondary and any other bands of a multi-speed modern trans probably wont see that much additional wear because the ring set is dealing with a moving car. In a powerglide, the low band is gone before anything else so that's the rebuild point.

OTOH, the majors unlock the TC between shifts for a reason, albeit for comfort and smoother shifts.

Worse case get an analysis on the fluid looking for band residue.

Thanks. Honda transmissions don’t have bands though, if that matters. What about extra wear from always running at a high line pressure?

I don't know about Honda but old GM vehicles with early th700 transmissions shifted between 3rd and 4th with the converter locked up.
Shifting with the converter locked up customer complaints because you could really feel it when it shifts and it would break transmission mounting bushings.

This trans will shift from 3rd to 4th locked as well, but I think only partially locked. It can’t be felt like when it is manually locked with high line pressure.

Yeah the early TH700 only had electronic on or off for lock up.
A PWM soft lockup came later for GM.
If you can't really feel it shift then there is some electronic or hydraulic trickery going on.

By all accounts I have been able to find soft grocery getter shifts ruin transmissions faster as it wears clutches faster than hard shifts.

Thanks. So I am right that disabling the pressure control solenoids so it holds a high pressure is actually better on the transmission? My old trans died shortly after I started messing with it, but at 243K miles I think it was just its time to go.

FWIW my '17 Fusion locks the converter after it shifts into 3rd, has a 6 speed trans
I'd like to know why the engineers chose to have it this way.
Not saying it's wrong, just curious.

Interesting. My guess would be because they found that 3rd gear is the earliest they can lock the converter while still shifting smoothly. I noticed that at least with my car, shifting it with the torque converter locked up feels a lot harsher in lower gears. A 1-2 shift locked up jerks the whole car and makes the engine surge and doesn’t feel happy. But a 2-3 or 3-4 shift locked doesn’t feel nearly as harsh for some reason. My guess would be because the car has more inertia at higher speeds, but I don’t know for sure.

This could also be because some people don’t like the immediate and direct response of getting on and off the throttle that occurs with a locked converter. I notice this more in lower gears. I like the direct response, but some people may feel like it’s harsh.

I had 2 options with my Allison 6sp install.
1 GM style, soft and squishy 1-5(1stOD) 5-6 locked shift
2 Allison style, 1-2,lock 3-6 locked shifts
GM went this way for a soft fill not longevity or controlling excessive heat.
Allison, went for longevity @ up to 26k lbs.
Ether way the TCM adjusts the apply and release solenoids timing(when) and rate (how much time it takes each) to make smooth shifts independent of controlling line pressure. Uncontrollable line pressure WILL destroy the trans with extremely violent shifts as timing and rate alone are inadequate.

Read up on how your particular trans controlls shift firmness. A shift kit may be the better option.

Thank you for all the great info, I really appreciate it! How exactly will my pressure control solenoid modifications destroy the transmission though? It now shifts noticeably firmer than stock, but I wouldn’t say that it is shifting violently at all. And I have stiff polyurethane engine and trans mounts, so if it was shifting hard enough to break thinks I would think I would feel it.

Also, how quickly would you expect these modifications to destroy the trans? I have been driving it about 6K miles this way and everything still seems fine as far as I can tell. If something was going to break from the hard shifts I would think it would have by now, but please correct me if I am wrong.

Like I posted earlier: get a fluid analysis done.

That will tell exactly what is in the fluid, like band material, chunks of gears with serial numbers, bananas, whatever.

IF there's nothing abnormal then you're not destroying your transmission no matter what anyone says.

You can either worry or be proactive.

Thank you. That's a great idea, I will look into that. However, I am reasonably sure I am not doing damage to my transmission simply by raising the line pressure, although I could be wrong and it would be nice to know for sure. I do not normally shift it with the converter locked, I only did a few times.

So the problem is if I have the fluid analyzed and everything is okay (which is what I would expect), I still don't know if leaving the converter locked while it shifts is harmful because I don't normally do that. I would have to allow it to shift locked for a few thousand miles and have the fluid analyzed again to know that. And I don't know what kind of damage could be done if I regularly shift with a locked converter and I would really rather not ruin the transmission I just bought and installed in my only functional car.

Also, I plan to install a magnetic inline filter because I recently replaced the magnetic drain plug with a temp sensor for my new transmission temp gauge, which is probably bad since these transmissions don't have a real filter. I am not sure how that would affect the fluid analysis though.

If the fluid is ok, that means your current process DOESN'T creat more noticeable wear, so you can continue the process with the exception of part fatigue which is random. It also gives you a baseline to compare future problems. I expect the changes to be dramatic, as it was in powerglides. Back in the day, if you got a whole summer out of racing one, you were happy as can be.

All the magnet will do is attract steel particles, which while are abrasive, and just means you are failing the steel parts: gears, rings, bearings. Aluminum and clutch pack particles will still fail bearings. The best is a filter in the cooler circuit.

Very helpful, thank you for the great info. So if I understood correctly, boosting the pressures probably isn’t doing significant damage since the trans is still alive and healthy (as far as I can tell) after 7K miles of running this way. Is that correct? Thanks

As I constantly say: if the fluid is the original color, has no new smells, particularly burnt smells, and doesn't feel gritty or have suspended particles, you are wearing it out at a typical rate.

From my experience, it can change in a weekend but I do evil things to them.
To me: as it wears it goes from magenta to red to brown.

The fluid looks and smells fine to me after 7K miles of running it this way. However, as I said, I don’t shift with a locked converter. If I consistently shifted with a locked converter, the fluid may be dirty by now. For that matter, the trans may be dead by now for all I know.

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

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.

Update: !’m up to 10K miles so far and everything is still going well. The trans is still shifting nice and hard as it always did and the fluid still has a red color to it, it doesn’t smell burned or have any signs of issues. I am probably going to have the fluid analyzed, but I am starting to think that if something was going to fail from hard shifts it would have by now. I will post fluid analysis results when I have them

Another update: I’m up to 12K miles on this transmission so far. I have good news and bad news. The good news is it’s still shifting great. Also, about 1k miles ago I changed the fluid. I also changed the filter because I wanted to cut the old filter open and inspect the filter media. The old fluid looked good. It wasn’t bright like the new fluid, but it was still very red and had no visible particles and it smelled and felt normal. The filter I installed still looked good, it didn’t have any large particles trapped in the media and the magnet I stuck to the bottom of the filter didn’t catch any large particles either. There was some very fine glitter stuck in the paper element, but the buildup was quite minimal and I don’t think that’s abnormal. After seeing how clean the filter looked I am planning to change it again when I reach 300K miles, so about 45K more miles.

The bad news is that the range sensor is starting to act up and I can’t easily buy one for this transmission. I tried installing the one from the old transmission, but it didn’t work because it has 6 positions (P R N D D3 2) and my JDM SLXA Stream transmission only has 5 positions (P R N D 2) and D3 is activated by a switch rather than a position on the shifter. I posted on a couple Honda forums I belong to asking if anyone has an SLXA range sensor and I haven’t heard from anyone yet, so this is definitely a problem. Hopefully I am able to find one soon, driving with a bad range sensor gets very old very quickly since I have to clear the codes every time I move the shifter (several times a day) since it sets a P0705 and goes into limp mode every time I move the shifter, and I have a habit of shifting to neutral at stop lights.