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Discussion Starter #1
OK, long story short. My X is 10-yr old and I plan on keeping it for another 2-3 years. Recently I have gotten a P0741 code which means that there is no lockup on T.C. Indeed, I have observed an increased freeway fuel consuption as described in a few posts, so the error is correct. The vehicle drives very well besides that, including in the city and on freeways (really, no way to tell that anything is wrong other than by fuel cons).

So my question is... I have read a lot of sources and spoke to a very experienced tranny shop manager and I am somewhat hearing that lock-up is not that critical after all. YES, it does reduce fuel consumption and YES it does reduce temperature (I have a giant aftermarket tranny cooler anyway), but other than those two things, if I monitored tranny temperature and changed the fluid often, say once a year just to be on a safe side, am I OK driving with no lockup on secondary roads at 80-90kmh and some freeways at maybe 100-110kmh? (lockup is apparently irrelevant/inapplicable under 80-90 kmh). To complicate things a bit... I tow a lot, specifically about 4500 lbs. So I am slightly concerned that the slip inside the T.C. will be more prominent and may lead to some quick component damage... But then... I am told that 15-20 years ago hardly any car had lockup TC to begin with so I should be OK (and the tranny shop manager too did not seem too concerned about my heavy tow load given my current TC condition). Yes, he did advise me to change/fix it, but he specifically did not mention that I will burn the fluid/tc/tranny in no time simply due to no lockup (I could tell he was honest enough NOT to try to sell me his services no matter what, but per my request, he was giving me more of a "buddy" advice to minimize cost if I only want to keep the car for 2-3 years). What he was saying sort of complements the theory that cars used to do just fine without lockup to begin with (other than they burned more gas than todays' cars with lockup).

Anyone experienced could chip in? Shall I go ahead and keep driving/towing as is? Does driving at 80-90 kmh on secondary roads (which is where I tow for the most part) really have anything to do with a lock-up on the torque converter? I simply don't want to dump money in vain to replace the whole thing now, since the new TC *may* not lockup at those speeds to begin with! (by design)
 

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The Torque Converter usually locks up above 45mph (72km/h). So, if you normally drive under this speed, then you are correct that, lockup or not, the point is moot.

Now, there are two reasons that I could think of that will result in the TC not locking up (there might be more but I can only think of two, being an amateur myself). First of all, the TC clutch may be worn out, in that case you have little choice but to replace the TC and the transmission since the clutch material is probably everywhere in the transmission by now, clogging up everything.

On the other hand, it might be that only the solenoid has burned out, in which case that can usually be replaced. For domestic cars I have owned before, specifically a Ford, that can be done rather quickly and inexpensively. However, I have no clue what's involved with the MDX, you just have to wait for better people to chime in.

If it's only a solenoid, and if (this is a big if) it's cheap to replace, what you plan to do (ignore it totally) could be "penny wise, pound foolish."

Good luck.
 

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Discussion Starter #3
The tranny shop guy said 9/10 it's not the cheap fix and the tranny has to come out ($2000-3000) so it seems completely not worth it since the car hardly drives/tows at freeway speeds and I only intend on keeping it for 2 more years or so...

Do you know if the TC has a chance to lock-up AT ALL under a very heavy load at, say, 100 kmh? (60 mph). Anyone knows?
 

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Yogi,

I don't know what year your MDX is, but here is the information for the 2001-2002 MDX.

You might have to drain the radiator and remove the radiator hoses to get to it since the TC lockup solenoid (and Shift Solenoid B) appear to be hidden beneath the radiator hoses. I can shine a light in there and see them, but there is no way my hands are small enough to get to them.

You can try measuring the resistance at the very least to see if it's within the range 12-25 Ohms. If it's open or shorted out, then maybe there is a chance for it.

Good luck
 

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Discussion Starter #5
Wow, thanks. I was just gonna go to the Acura dealer to get the same info.

In the meantime, I found this (not specific to Acura).... Would that basically mean that under my not-so-light load , the TC lockup is completely inapplicable/irrelevant?

"The ECU will often lock up the torque converter when the car reaches a particular speed and gear but usually only under low load conditions. "
 

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Discussion Starter #7
2003 MDX.

Yes, I do have a large aftermarket cooler. About 8x6 inches that sits in front of the rad.
 

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Discussion Starter #8
And I've just found this to suggest even more that I should disregard lack of lock up.... (again, not specific to Acura)

"The TCC is made to engage usually only in the top gear when the car is cruising, not accelerating."

I never tow in the 5th...
 

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The TCC will only engage under very light load, the slightest acceleration will disengage the TCC, think of it as an overdrive 6th gear. Strictly engineered to aid fuel economy, mass introduction in the early eighties on US domestic cars, along with mass failures/problems, although usually a failed solenoid in those days.

If I were in your position, I'd just drive it until a driveability problem forced me to repair or sell it. As always, YMMV:)
 

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Discussion Starter #10
EXACTLY!

You guys have answered my questions... That was my thinking. TC lockup is completely inapplicable when towing a massive boat at 90-100 kmh (55-60 mph). So probably no reason to worry at all, kind of what the tranny shop manager said.

Much thanks guys. I am at a complete ease now (BTW, the shop told me that it would cost me the same to put a used tranny in later, say after mine dies, as it would to fix the no lockup issue now, if the tranny had to be removed). But at least I have a nice shot at spending exactly $0.
 

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Discussion Starter #12
Rally, this was precisely the plan. (and yes, I've already been towing in D4 and drained 3 qts annually), so I suppose no change to my driving whatsoever. I got an unintended crash course in torque converters because of my P0741 error code though. LOL. Too much knowledge can't hurt, I suppose LOL
 

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Discussion Starter #13
OK guys something else is bugging me now, hope someone with more insider knowledge can explain.... if the lock-up usually occurs at about 50 mph or higher because at that speed there are less frequent wide-open throttle applications, why does the lock-up shuts off ("unlocks" if you will) if a driver, say, applies 50% throttle (assuming there is no downshift)? Since the lock-up clutch is already engaged and assuming the engine has enough power to accelerate without downshifting, why can't the torque converter lock-up clutch remain engaged while the vehicle promptly accelerates? Is the lock-up clutch not designed to withstand that much force, ie: is it only designed to work when very little throttle/force is being applied?
 

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It's basically like trying to accelerate from a stop in second gear, engine is not in the power band needed to accelerate smoothly and will likely cause a shudder, which happens on many older vehicles anyway until the pcm decides the parameters for disengagement exist. The algorithms used in the software for newer transmissions with 6 + gears have gotten better and the time to switch states has become much shorter.
 

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2003 MDX.

Yes, I do have a large aftermarket cooler. About 8x6 inches that sits in front of the rad.
this might be a silly question, but is an 8x6 cooler considered big?

I bypassed my internal radiator cooler and instead isntalled a 8 x 15 aftermarket external cooler. However, I always thought mine was on the smaller side.

Sincerely
 

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Discussion Starter #16
this might be a silly question, but is an 8x6 cooler considered big?

I bypassed my internal radiator cooler and instead isntalled a 8 x 15 aftermarket external cooler. However, I always thought mine was on the smaller side.

Sincerely
I was comparing it to the OEM "extra" tranny radiator (a silly tube with fins). So in comparison, mine is massive and judging by the OEM extra cooler recommended for heavier towing, mine should cool the hottest tranny within the MDX towing capacity.

Yours might be a total overkill.... Unless you tow way more than MDX is rated for.
 

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Yours might be a total overkill.... Unless you tow way more than MDX is rated for.
I see what you are saying and from that standard, mine might be an over kill. HOwever I also eliminated the internal radiator cooling part of the tranny cooling system. I am not sure how much the radiator really cooled the tranny oil considering radiators get pretty hot too but in my opinion the risk of a mdx radiator failure and the impact on the tranny was not worth it.

After towing, I occassionally stick my fingers in the front grill to feel how hot my external cooler lines get and they do get hot but not scortchingly hot so I think it is doing the job.

I also tow a boat but mine is only 2500 lbs but with equipment kids etc I would say my total weight is 3200 which is still below the tow limit. I am trying my best to get my money's worth out of this vehicle without unnecessarily risking a major repair.
 

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Discussion Starter #18
Yeah, I do stick my fingers in there too. LOL. Great minds think alike.

From what I heard... yeah the bottom rad cooler is useless for cooling (and super prone to catastrophic failures as you know, fingers crossed NOT with my new aftermarket radiator!) but I've read that it is advisable to have it... for the opposite reason! Ie. to bring the fluid to the normal working temperatures in Winter!

And that does make perfect sense. Basically coolant gets hot rather quickly on the MDX so it helps get the ATF warm as well. I seriously doubt is cools it at all (the idea is plain stupid, ie. hot fluid cooling another hot fluid...weird).

But unless you live in a warm climate, with your oversized ATF cooler, you might be running your tranny on the cold side! It may simply not have enough friction to heat itself up especially since the elimination of the rad atf cooler altogether.
 

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But unless you live in a warm climate, with your oversized ATF cooler, you might be running your tranny on the cold side! It may simply not have enough friction to heat itself up especially since the elimination of the rad atf cooler altogether.
I live in Central Florida. Only hell consistently registers hotter temperatures. So I dont have to worry about the need for quick warm ups in the winter.

I agree with you on all points.
 

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Discussion Starter #20
Lucky you, then! Yes, I have seriously considered bypassing the rad too, but living in a cold climate, I would have been doing myself, or my tranny specifically, more of a disservice. They should basically do a recall on those stupid OEM radiators that fail on just about everyone and in such a horrible way that the tranny may go bust at the same time (thank God my wife saw the puddle of fluid before I put it in D that day....).
 
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