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Thread: P0740 - TCC Failure

  1. #1

    Default P0740 - TCC Failure

    Yesterday, the wife was starting the Jeep to run an errand and the CEL came on; ran the code today when I was at work and it equates to a Torque Converter Clutch failure (Factory Service Manual actually states TCC/PTU). Now, I'm not overly familiar with automatic trannys but I fail to see how the torque converter clutch is failing on startup. So, my first question is, what does a failed TCC mean? Tranny rebuild (which would suck because I just did a full filter/fluid service on it - pan drop, not flush)? Also, what is the PTU? I know from Mitsubishi's the PTU is the Power Transister Unit which is ignition related; I'm not sure in what regard Jeep is using for this abbreviation (I didn't take the time to look it up in the book - I know, now I'm being lazy - sorry) and how it relates to the transmission. Third, is this failure more common to be a module failure or a trans issue? Is it safe to drive on until I can get the problem fixed (the code was cleared when it was run, it has not come back on as of yet and has been started 5 additional times since it was cleared)? I did some searching on the forum but did not come up with much (a few XJ issues but I do not know the compatibilities between an XJ and a WJ - I'm a bit of a Jeep noob). Anyhow, any info or advice would be greatly appreciated and I think you in advance for your time to read this.

    Application:
    2001 Jeep Grand Cherokee Limited 4x4 4.7L Quadra Drive 545RFE trans with ~120k miles.

  2. #2
    Registered tbm5690's Avatar
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    Should be fine to still driving it, especially if the CEL is now off. Does the TC still lock up properly on the highway?
    Rare 2001 WJ S/A Laredo, loaded, 4.7L
    -Airraid MIT paired with a K&N panel filter
    -Flowmaster 50 catback
    -new set of Destination ATs

  3. #3

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    I have very rarely had the Quadra-Drive system actually engage the front wheels on me so I am not certain. I know that if I am to shift it to 4 high or 4 low that it engages just fine.

  4. #4

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    Quote Originally Posted by AlmosN8kd View Post
    Yesterday, the wife was starting the Jeep to run an errand and the CEL came on; ran the code today when I was at work and it equates to a Torque Converter Clutch failure (Factory Service Manual actually states TCC/PTU). Now, I'm not overly familiar with automatic trannys but I fail to see how the torque converter clutch is failing on startup. So, my first question is, what does a failed TCC mean? Tranny rebuild (which would suck because I just did a full filter/fluid service on it - pan drop, not flush)? Also, what is the PTU? I know from Mitsubishi's the PTU is the Power Transister Unit which is ignition related; I'm not sure in what regard Jeep is using for this abbreviation (I didn't take the time to look it up in the book - I know, now I'm being lazy - sorry) and how it relates to the transmission. Third, is this failure more common to be a module failure or a trans issue? Is it safe to drive on until I can get the problem fixed (the code was cleared when it was run, it has not come back on as of yet and has been started 5 additional times since it was cleared)? I did some searching on the forum but did not come up with much (a few XJ issues but I do not know the compatibilities between an XJ and a WJ - I'm a bit of a Jeep noob). Anyhow, any info or advice would be greatly appreciated and I think you in advance for your time to read this.

    Application:
    2001 Jeep Grand Cherokee Limited 4x4 4.7L Quadra Drive 545RFE trans with ~120k miles.
    When you start the Jeep, the PCM tests the TCC circuit, if the resistance is too low or too high through the solenoid, it will throw a code. If the code is gone and the TCC is locking on the highway, I wouldn't worry about it unless it happens again.

  5. #5

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    Quote Originally Posted by AlmosN8kd View Post
    I have very rarely had the Quadra-Drive system actually engage the front wheels on me so I am not certain. I know that if I am to shift it to 4 high or 4 low that it engages just fine.
    The torque converter has nothing to do with quadra-drive.

    If you want to know if the TCC is locking on the highway, drive at a steady speed on the highway, flat ground, light throttle for a little while, and maintain your speed, then without taking your foot off the gas, tap on the brake pedal with your left foot, not enough to actually slow down the Jeep but just enough to turn on the brake lights. If the RPM's jump by about 200-300 RPM then go back down, the TCC is locking, If the RPM's don't change a bit, the TCC probably isn't locked.

  6. #6

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    Sorry, when tbm said TC in his post, I instinctively thought Transfer Case due to several conversations regarding 3/Ss. My apologies.

    The Jeep drives just fine for the most part, I have noticed some shift lag and a bit of hard shifting between 4th and 5th; especially when not completely warmed up.

    I'll perform the brake-TCC locking test sometime and get back to you.

  7. #7
    Registered tbm5690's Avatar
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    Quote Originally Posted by AlmosN8kd View Post
    Sorry, when tbm said TC in his post, I instinctively thought Transfer Case due to several conversations regarding 3/Ss. My apologies.

    The Jeep drives just fine for the most part, I have noticed some shift lag and a bit of hard shifting between 4th and 5th; especially when not completely warmed up.

    I'll perform the brake-TCC locking test sometime and get back to you.
    You shouldn't have a hard shift from 4th to 5th...in fact it should be one of the smoothest shifts as you are engaging in O/D. When it's decently cold out you shouldn't be shifting into 5th until the transmission is at full (or close to) operating temperature. The PCM should not be allowing you to ride in O/D until the components are warm.
    Rare 2001 WJ S/A Laredo, loaded, 4.7L
    -Airraid MIT paired with a K&N panel filter
    -Flowmaster 50 catback
    -new set of Destination ATs

  8. #8

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    It is possible that I am confusing what is actually going on in the transmission; I wasn't aware of the temperature requirement for overdrive. Let me get the braking test done and we'll go from there. Thanks for your help thus far guys.

  9. #9

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    Ok, I did the braking test tonight as outlined by twojeeps; I was getting pretty much no movement on engine speed while I simulated load on the trans (by simulated, I mean what you told me, apply the brake but do not put enough pressure to engage them) at varying speeds (25-30, 45-50, 70-80). I ran the test multiple times, I never saw a dramatic fluctuation in engine speed (under one test on the HWY I thought I did but I think it was from applying too much brake and actually loading the engine). The CEL is still out and has remained clear ever since the code was cleared the other day (basically, I'm not sure why I got an error the other day yet the Jeep is failing the test - it would lead me to believe that the failed component would cause the code to emerge again; but then again, what do I know). Anyhow, what's this telling me? The torque converter clutch has failed? The Jeep is driveable? Is there a subsequent test to narrow down the fault? What is involved with a TCC repair; I trans rebuild? Again, sorry for all the questions but I do appreciate everyone taking the time to read this ramble and post up some info to help me out.

  10. #10

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    I doubt the TCC itself failed, the solenoid is more likely. I'd not take the tests as definitive, if you weren't traveling at a constant speed, flat ground, light throttle, at highway speeds, the TCC might not have been locked.

  11. #11
    Registered tbm5690's Avatar
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    Your symptoms describe mine about 2 years ago...drives fine but at highway speeds the TC doesn't function normally. The difference, though, is that you received a specific TC code...I only got the generic P 0700 with the key trick. With mine the CEL would only go on after a considerable amount of highway driving...at times more than an hour. When it was diagnosed I received a TC solenoid failure/not locking sort of thing, as well as low pressure, which could have caused the failure. All in all, I pretty much had a rebuild done...bill came to...gasp...$2600. A ton of the labor/parts was for them to replace the pump to fix the pressure problem...the pump is extremely painstaking to get to. Also, the 545 has the most expensive parts and is one of the more complex of all Chrysler transmissions...so that weighed heavily on price. If all you have is a TC solenoid should be more bearable. Had it done by a reputable shop in town.

    Don't want to prematurely scare you, but what I would do at this point is find a reputable transmission shop in town and get them to give you a diagnosis. Whatever you do STAY AWAY FROM THE DEALER. Ask me why.
    Rare 2001 WJ S/A Laredo, loaded, 4.7L
    -Airraid MIT paired with a K&N panel filter
    -Flowmaster 50 catback
    -new set of Destination ATs

  12. #12
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    I had a P0740 code and ended up having my transmission rebuilt.
    Total bill: $2200.00
    02 Limited 4.7 Quadradrive
    245/70/16 Mastercraft Courser AT
    16x7 Cragar
    159,xxx miles

  13. #13

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    Well, I had typed a huge response earlier but the server went down or something and it didn't post. Anyhow, I was driving today and theCEL came on again; this time it was accompanied by the TRANS OVER TEMP light and some issues transitioning between neutral/idle and driving. When I parked, I checked the fluid which looked a little low so I added a quart because I had it with me. Anyhow, looks like I'm going to be doing a rebuild. I had a bunch of questions pertaining to this in my post that didn't make it online so when I get home and back on my computer (I'm posting from my phone while I'm out right now) I'll put up the questions I had when I attempted to post earlier. In the meantime, I am planning on driving home (about an hr on the HWY) and parking this beast for awhile. Thoughts?

  14. #14

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    If you got an overheat, that's almost a sure sign of needing a rebuild. A faulty TCC solenoid should not cause a trans to overheat - if it did, transmissions built before the days of TCC's would have overheated all the time.

    My guess is the code was triggered from a speed difference in the engine and output speed sensor, which could be TCC slipping, but could also be worn clutches in the tranny, meaning you need a rebuild.

  15. #15

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    Ok, here is what I was attempting to post before the post I put up at 11:40pm today:

    Quote Originally Posted by AlmosN8kd
    Well, I think I'll continue to drive it and see if it throws the code again; if it does, then I'll look at rebuilding it or replacing it (the Jeep). In the meantime, is there a way to differentiate between the pump (not sure which pump we're talking about exactly, I'm assuming the one pumping fluid throughout the trans) and the solenoid (as in a different test)?

    As for rebuilding, unfortunately, I do not trust most mechanics so the plan was to do it myself. I would go directly to the dealer for the parts but not to have them do the work (I don't need to ask why). However, since it has been about 10 years since I have been inside an automatic transmission (I started doing automotive repairs in '91, only had a couple of transmission jobs come through before autowork became a hobby, I was generally doing engine work when the transmissions came in but I have built a few manual transmissions - I know, completely different) I'm gonna have to get a buddy of mine here to look over my shoulder. Now, I've never had to do any major repairs on the Jeep but where would be a good place to get OEM parts online? Thus far, I've always gone to my local dealer to get what I needed as it was usually something simple (like a trans filter) but if I am buying a large number of parts (like clutch rings and what not) in the trans I'd rather avoid paying list price unless I have to. Is there a common list of replacement parts for the trans (like, a list of things that should be replaced anytime the transmission is out or open since it is the same amount of work to replace them later)? How about a parts search program (for those familiar with Mitsubishis, they have the Computer Aided Parts Search (CAPS) program - has saved me lots of time over the years) so that I can look up the part numbers myself?
    Anyhow, on the way home, the TRANS OVER TEMP light came on again. So, my guess is that I have a pump failure causing excessive clutch plate wear, resulting in slippage inside the trans, and resulting in the CEL. This is completely out of my ass, I really am guessing here but I think it is obvious that I need a rebuild; so, does anyone have the answers to the questions I put up at the end of the "missing" post?

  16. #16

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    Quote Originally Posted by AlmosN8kd View Post
    Ok, here is what I was attempting to post before the post I put up at 11:40pm today:



    Anyhow, on the way home, the TRANS OVER TEMP light cambuy e on again. So, my guess is that I have a pump failure causing excessive clutch plate wear, resulting in slippage inside the trans, and resulting in the CEL. This is completely out of my ass, I really am guessing here but I think it is obvious that I need a rebuild; so, does anyone have the answers to the questions I put up at the end of the "missing" post?
    A pump failure would result in no hydraulic pressure, and no drive in the trans. That's not the problem, and besides the pumps in these trannys are just about bulletproof.

    As for a rebuild, no need to go to the dealer, you can buy kits with new clutches and steels for a few hundred.

    You should try the easy stuff before you tear into it, just in case. Possible that the cooler is clogged, you say you changed fluid and filter, if it was the first time ever, it can dislodge crap into the valve body and cooler and cause problems. Do a flow test, i.e. disconnect return cooler line and run engine, it should pump a quart in about 20 sec.

    Check resistance of TCC circuit (probably in FSM). Check to see if it's being activated (tap into wire, see if voltage changes at highway speeds.) Stuff like that.

  17. #17

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    I have changed the filters twice; well, I changed the large one twice, and the cooler return filter once. About 9 months ago, I bought the filter to replace it, got under there, did the work, didn't realize there were two filters; put it all back together as I didn't have the time necessary to wait for the second filter (I was moving from WA to AL and couldn't wait). Anyhow, about a month or two ago, I changed both filters and the fluid again as I noticed it being a little hard in shifting (perhaps it is just me, I don't drive the Jeep too often and all of my other vehicles are manual). After the service was completed, I didn't notice a significant change in shifting when cold (but when warm it was a bit smoother) and then the other day this problem rears up. So, perhaps the problem is that the previous owner never changed the filters on the trans (damn half-assed shops doing flushes all the time) and now something is failing because of what ever was keeping things working is no longer there (I had a similar problem about 9 years ago with an old Ford FMX trans, did the service on it, and then it stopped workin needing a rebuild). I'll try the two tests but being that it was giving driveablity problems I'm suspecting that even if the source of the problem wasn't the trans that the damage is done needed rebuild. As for buying parts/kits; is there a site you recommend?

  18. #18

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    New development.

    I told the wife that she could drive the Jeep around town to run errands but if the TRANS OVER TEMP light came on that she should park and stay there for a bit to allow things to cool down. Also, I told her not to run on the HWY for much more than a couple of exits as needed to get across town for regular errands. Anyhow, yesterday she was running errands and she had two events happen. One, the CEL cleared on its own. Two, while idling at a light, the engine died randomly; I equated it to sitting at a light with a manual trans, one foot on the brake, one on the clutch and then letting the clutch out = stall; basically, I was thinking the TCC did not function properly and caused the engine to die in a similar manner. Is this feasible?

    TwoJeeps, I have not run the two subsequent tests.

  19. #19
    Registered Majoraslayer's Avatar
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    I have a '94 ZJ, so this may be completely different. However, a few months ago I was having trouble with the transmission slipping, and sometimes the Jeep would just randomly shut down going down the road. It would act like the engine overheated, but the engine would be fine. It turned out that the slippage was caused by the transmission needing to be topped off (apparently, the fluid must be all the way to the top line, not a drop less). I think it was shutting down the engine when it detected the transmission getting too hot.
    My Current Vehicles:

    1989 Jeep Wrangler (4.2L, Auto)
    1974 Jeep CJ5 (V8 3-Speed)
    1994 Jeep Grand Cherokee Limited 4x4 (My Wife's)
    1988 Chevrolet C1500 Scottsdale
    1999 Chevy Blazer 4x4

  20. #20

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    Quote Originally Posted by AlmosN8kd View Post
    New development.

    I told the wife that she could drive the Jeep around town to run errands but if the TRANS OVER TEMP light came on that she should park and stay there for a bit to allow things to cool down. Also, I told her not to run on the HWY for much more than a couple of exits as needed to get across town for regular errands. Anyhow, yesterday she was running errands and she had two events happen. One, the CEL cleared on its own. Two, while idling at a light, the engine died randomly; I equated it to sitting at a light with a manual trans, one foot on the brake, one on the clutch and then letting the clutch out = stall; basically, I was thinking the TCC did not function properly and caused the engine to die in a similar manner. Is this feasible?

    TwoJeeps, I have not run the two subsequent tests.
    Yep, perfectly feasible. The TCC on both of my ZJ's sometimes drag at idle, mostly when shifting from N to D or R.

    A simpler way to check cooler operation is to get a non-contact thermometer, you can get a cheap pocket unit from HF, and measure the temp of the cooler lines themselves. Do it on the metal part of the lines a ways away from the tranny and also measure pan temp for a baseline. The three temps should be similar.

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