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Old 11-01-2019, 10:43 AM   #1 (permalink)
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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.


Last edited by EcoCivic; 11-01-2019 at 10:44 AM.. Reason: Added vehicle info
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Old 11-01-2019, 10:59 AM   #2 (permalink)
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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.
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Old 11-01-2019, 11:07 AM   #3 (permalink)
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Quote:
Originally Posted by Piotrsko View Post
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?

Last edited by EcoCivic; 11-01-2019 at 11:31 AM..
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Old 11-01-2019, 01:34 PM   #4 (permalink)
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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.
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Old 11-01-2019, 01:35 PM   #5 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
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 canít be felt like when it is manually locked with high line pressure.
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Old 11-01-2019, 01:42 PM   #6 (permalink)
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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.
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Old 11-01-2019, 01:45 PM   #7 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
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.
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Old 11-01-2019, 02:23 PM   #8 (permalink)
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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.
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Old 11-01-2019, 02:46 PM   #9 (permalink)
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Quote:
Originally Posted by Keito View Post
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.

Last edited by EcoCivic; 11-01-2019 at 02:59 PM.. Reason: Added info
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Old 11-02-2019, 01:12 AM   #10 (permalink)
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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.

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