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Am I killing my transmission? #5334491 01/28/20 08:52 AM
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Avery4 Offline OP
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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’m a performance guy and I like hard shifts, but I certainly don’t want to destroy my new (to me) JDM SLXA 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 (I control it manually with a switch). 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 10K 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.

I just did a drain and fill on the trans yesterday and I didn’t see anything disturbing in the old fluid after 10K miles of use, but I have an engine oil filter on my trans to catch particles, so I may not see anything. I could upload a pic of the old fluid if that would be helpful, I use Valvoline Import Full Synthetic ATF.

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

Re: Am I killing my transmission? [Re: Avery4] #5334500 01/28/20 09:09 AM
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madRiver Offline
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Quote
.......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.


¯\_(ツ)_/¯

I would guess you may damage it based on above.

Re: Am I killing my transmission? [Re: Avery4] #5334501 01/28/20 09:09 AM
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skyactiv Offline
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I started my mechanics career out at a Honda dealer. I saw my fair share of dumb mods people did to Civics. How can anyone here answer this, do we have test data to back it up? Is someone gonna say "a harder shift is better for the clutch pack life"?


Wife: 15' Audi A4 quattro 6 speed manual
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Re: Am I killing my transmission? [Re: Avery4] #5334512 01/28/20 09:23 AM
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What made you mod the solenoids, especially if, as you say, you don't much about transmissions?

It seems odd to ask a question about whether this is safe to do 10k miles AFTER modding. Most people do their research beforehand.


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Re: Am I killing my transmission? [Re: madRiver] #5334513 01/28/20 09:23 AM
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Avery4 Offline OP
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Originally Posted by madRiver
Quote
.......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.


¯\_(ツ)_/¯

I would guess you may damage it based on above.

I am not an idiot about transmissions, I understand the basics of how they work and I tore this trans down enough to change the internal filter before I installed it, I just don’t know everything there is to know about them.

Re: Am I killing my transmission? [Re: Avery4] #5334514 01/28/20 09:26 AM
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Spktyr Online Content
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Unless the torque converter clutch is designed to be locked while shifting, shifting it while locked places inordinate amounts of stress on it and greatly shortens its life. This is the general rule - learned this when converting to a 700R4 in a formerly three speed car and again when I was working with an E4OD, in both cases either programming or manually controlling features in custom installs. I corresponded with then-current and retired Ford and GM engineers about that, and from my further research I believe the rule applies to pretty much all conventional slushboxes.

Keep in mind that the TCC isn't actually all that strong - really can't take the full rated power - as it's often a tiny little thing made of carbon fiber. The factories all disengage the TCC when you accelerate more than lightly (some allow moderate accel, some don't) for a reason, and they often only engage it in top gear - or sometimes in middle gears under light acceleration or cruise only. Go google the TCC for, say, a 4L60E and then compare the size of the TCC mechanism to the primary bands/clutches in the 4L60E itself that are supposed to take full load. You should be able to see a large size difference, which means there's a large torque handling difference.

For my projects that led me to do the research? In the end, I decided to include TCC lockup *disable* switches in each vehicle, much like the factories did, for the same reasons they did. High/steep/hot work, towing heavy loads, etc. I did not include manual lockup switches or to program the trans to lock up at anything other than schemes resembling factory.

It's your car, you do what you want. But if you continue with the rig you have now, I'd suggest having a spare trans handy, because when the TCC goes, shrapnel and glitter will go everywhere and you're looking at a full rebuild to get it all out, not just a TC swap.

Last edited by Spktyr; 01/28/20 09:49 AM.
Re: Am I killing my transmission? [Re: Spktyr] #5334515 01/28/20 09:35 AM
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Avery4 Offline OP
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Originally Posted by Spktyr
Unless the torque converter clutch is designed to be locked while shifting, shifting it while locked places inordinate amounts of stress on it and greatly shortens its life. This is the general rule - learned this when converting to a 700R4 in a formerly three speed car and again when I was working with an E4OD, in both cases either programming or manually controlling features in custom installs. I corresponded with then-current and retired Ford and GM engineers about that, and from my research I believe the rule applies to pretty much all conventional slushboxes.

Exactly the kind of information I was looking for, thank you! I know for a fact that my trans shifts from 3rd to 4th locked stock, but I presume shifting from 2nd to 3rd locked puts a lot more stress on things, at least that’s what it feels like

Re: Am I killing my transmission? [Re: Avery4] #5334523 01/28/20 09:46 AM
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Spktyr Online Content
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Originally Posted by Avery4
Exactly the kind of information I was looking for, thank you! I know for a fact that my trans shifts from 3rd to 4th locked stock, but I presume shifting from 2nd to 3rd locked puts a lot more stress on things, at least that’s what it feels like


It may perform the 3-4 shift while locked under light to mild acceleration, but it's *very* rare to find one that will do that under moderate to hard acceleration due to the stress (there *are* transmissions out there with TCCs that are literally the size of soup cans or larger and they are usually associated with schemes to lock the TCC from 2nd on - they are relatively rare). Usually the scheme is to lock the TCC in top gear when you are at light to mild acceleration. Again, most TCCs are fairly fragile.

See my edits above.

Edit: And yes, usually the stress between lower gears is considerable because they're usually widely spaced in terms of ratios. Often the last two ratios will be a lot closer than the first two and the wider the gap the more stress you've got when shifting.

Edit 2: You may also want to rethink raising line pressure - that can have some unfortunate consequences long term as well as the higher pressure can break things. There's a reason "shift kits" exist - they don't necessarily only raise overall line pressure, and they've had a lot of development work done to make sure they don't break hard parts.

Last edited by Spktyr; 01/28/20 09:53 AM.
Re: Am I killing my transmission? [Re: Avery4] #5334531 01/28/20 09:52 AM
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Pelican Offline
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Originally Posted by Avery4
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’m a performance guy and I like hard shifts, but I certainly don’t want to destroy my new (to me) JDM SLXA 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 (I control it manually with a switch). 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 10K 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.
I just did a drain and fill on the trans yesterday and I didn’t see anything disturbing in the old fluid after 10K miles of use, but I have an engine oil filter on my trans to catch particles, so I may not see anything. I could upload a pic of the old fluid if that would be helpful, I use Valvoline Import Full Synthetic ATF.
Thank you very much in advance, I really appreciate your help.


Generally the more overlap (smoothness) in gear changes the more clutch material is used, the more abrupt the less. Factory settings are a compromise between what the transmission needs to last a reasonable amount of time and what is acceptable to the buyer.

Re: Am I killing my transmission? [Re: Avery4] #5334549 01/28/20 10:15 AM
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Donald Offline
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I would start looking for a remanufactured transmission and have it on hand to reduce the downtime when the current one fails.

But a 15 yr old vehicle. So you will tow it to the boneyard when the transmission fails?

Is this a DD or a spare vehicle you can play around with?

How old are you?

Last edited by Donald; 01/28/20 10:16 AM.

2015 Ford F-250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: Am I killing my transmission? [Re: Spktyr] #5334565 01/28/20 10:29 AM
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Avery4 Offline OP
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Originally Posted by Spktyr
Originally Posted by Avery4
Exactly the kind of information I was looking for, thank you! I know for a fact that my trans shifts from 3rd to 4th locked stock, but I presume shifting from 2nd to 3rd locked puts a lot more stress on things, at least that’s what it feels like


It may perform the 3-4 shift while locked under light to mild acceleration, but it's *very* rare to find one that will do that under moderate to hard acceleration due to the stress (there *are* transmissions out there with TCCs that are literally the size of soup cans or larger and they are usually associated with schemes to lock the TCC from 2nd on - they are relatively rare). Usually the scheme is to lock the TCC in top gear when you are at light to mild acceleration. Again, most TCCs are fairly fragile.

See my edits above.

Edit: And yes, usually the stress between lower gears is considerable because they're usually widely spaced in terms of ratios. Often the last two ratios will be a lot closer than the first two and the wider the gap the more stress you've got when shifting.

Edit 2: You may also want to rethink raising line pressure - that can have some unfortunate consequences long term as well as the higher pressure can break things. There's a reason "shift kits" exist - they don't necessarily only raise overall line pressure, and they've had a lot of development work done to make sure they don't break hard parts.

Originally Posted by Spktyr
Originally Posted by Avery4
Exactly the kind of information I was looking for, thank you! I know for a fact that my trans shifts from 3rd to 4th locked stock, but I presume shifting from 2nd to 3rd locked puts a lot more stress on things, at least that’s what it feels like


It may perform the 3-4 shift while locked under light to mild acceleration, but it's *very* rare to find one that will do that under moderate to hard acceleration due to the stress (there *are* transmissions out there with TCCs that are literally the size of soup cans or larger and they are usually associated with schemes to lock the TCC from 2nd on - they are relatively rare). Usually the scheme is to lock the TCC in top gear when you are at light to mild acceleration. Again, most TCCs are fairly fragile.

See my edits above.

Edit: And yes, usually the stress between lower gears is considerable because they're usually widely spaced in terms of ratios. Often the last two ratios will be a lot closer than the first two and the wider the gap the more stress you've got when shifting.

Edit 2: You may also want to rethink raising line pressure - that can have some unfortunate consequences long term as well as the higher pressure can break things. There's a reason "shift kits" exist - they don't necessarily only raise overall line pressure, and they've had a lot of development work done to make sure they don't break hard parts.
Thank you for all the great information! Yes, my TCC is pretty small. I cut my old torque converter open and the clutch is just a ring of friction material about 8 inches in diameter and about 1/2 inch wide, it’s amazing that such a little clutch can handle so much power! Even though my engine is making about 20-30HP more than stock, I can’t get the TCC to slip even by flooring it, it holds solid. Amazing!

That’s a great point about beating on the hard parts more, I thought about that but I don’t know that it is shifting hard enough to break anything. Even with my stiff polyurethane motor and trans mounts I don’t feel like it is slamming into gear (by my standards anyways). Also, if something was going to break, I would think it would have done it by now, but feel free to correct me if I am wrong.

What would you expect the effect on clutch longevity to be? I would expect longer, but again I’m no expert here.

Re: Am I killing my transmission? [Re: Donald] #5334569 01/28/20 10:33 AM
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Avery4 Offline OP
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Originally Posted by Donald
I would start looking for a remanufactured transmission and have it on hand to reduce the downtime when the current one fails.

But a 15 yr old vehicle. So you will tow it to the boneyard when the transmission fails?

Is this a DD or a spare vehicle you can play around with?

How old are you?

I am probably going to get another one of these JDM SLXA transmissions when I find a good deal, I plan to keep this car forever so I will need it eventually. This is my daily driver right now, both of my other vehicles are down at the moment

Re: Am I killing my transmission? [Re: Pelican] #5334570 01/28/20 10:35 AM
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Originally Posted by Pelican
Originally Posted by Avery4
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’m a performance guy and I like hard shifts, but I certainly don’t want to destroy my new (to me) JDM SLXA 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 (I control it manually with a switch). 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 10K 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.
I just did a drain and fill on the trans yesterday and I didn’t see anything disturbing in the old fluid after 10K miles of use, but I have an engine oil filter on my trans to catch particles, so I may not see anything. I could upload a pic of the old fluid if that would be helpful, I use Valvoline Import Full Synthetic ATF.
Thank you very much in advance, I really appreciate your help.


Generally the more overlap (smoothness) in gear changes the more clutch material is used, the more abrupt the less. Factory settings are a compromise between what the transmission needs to last a reasonable amount of time and what is acceptable to the buyer.
That is what I thought. My understanding was that the shifts are so slow from the factory because most people don’t like hard shifts, not because that is best for longevity. Would you expect that clutch longevity may be improved by my modifications since it now shifts much quicker? Thanks

Re: Am I killing my transmission? [Re: Avery4] #5334605 01/28/20 11:29 AM
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Originally Posted by Avery4
...I plan to keep this car forever so I will need it eventually. This is my daily driver right now, both of my other vehicles are down at the moment

Some people learn best by doing. You seem like you might be one of those folks.
If your goal is to learn transmission repair and tuning, might I suggest choosing a vehicle other than your daily driver especially when your two other cars are not currently working?


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Re: Am I killing my transmission? [Re: Imp4] #5334681 01/28/20 01:02 PM
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Originally Posted by Imp4
Originally Posted by Avery4
...I plan to keep this car forever so I will need it eventually. This is my daily driver right now, both of my other vehicles are down at the moment

Some people learn best by doing. You seem like you might be one of those folks.
If your goal is to learn transmission repair and tuning, might I suggest choosing a vehicle other than your daily driver especially when your two other cars are not currently working?


Your daily driver should be driven easy since you need the vehicle to get you from point A to point B. You wanna drive your other vehicle hard. you will have problems eventually and it will not be good. From what I have read a manual trans is best to have fun with since all you may need to replace is the clutch.

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