Having owned my own transmission shop from 1981 to 2006 (I sold it) I am more than qualified to discuss a code p740. One of the most common codes too.
We recieved this question below and I though it would be a great time to speak on this.
Here is the question: “i got a 2001 grand caravan sport 3.3 v6 41te a604 w/ a check eng code p740. after getting shafted by some shops w/trial and error cures ex; replaced the trans soleniod ,changed the fluid and filter no cure. now there is a slight slip upon takeoff when driving . my question is should i now replace the torque converter and the pump seal. will this fix my p740 code problem????”
Code P0740/p740: Torque Converter Clutch Circuit Malfunction. This is a fairly complicated issue. It will take more than one article to address the issue. Realistically speaking without good reliable diagnostic techniques by a competent mechanic many folks will get the same result as the individual who asked this question. I’m not going to get super detailed in this post, I want to answer the question. I do think that a detailed post on the symptom itself and the many issues that can cause it should be discussed. I also would like to explain exactly what a TCC (torque converter clutch) is.
Briefly, a TCC is a clutch inside the torque converter (another subject all together) that when applied acts in essence like an other overdrive gear. It is a fuel economy feature that has been used for over 20 years now. The TCC systems have evolved with the continuing evolution of the automatic tranmsission.
As you can see in this question, many shops just try the hit and miss method, like replacing parts, which is expensive and irresponsible. However I think the bulk of shops know how to handle this properly. Basically the symptom feels something like #1. running over a washboard at 30 to 50 MPH (miles per hour) or #2. in some cases it actually stalls the engine violently as you roll to a stop. The problem is the torque converter, but that does not mean it needs repalcement.
Automatic transmissions are like the human body, a symptom is not always the component’s fault. For instance, if you have conggestive heart failure, usually you get water buildup in your legs and lungs. Your legs and lungs are not bad in reality, it is all caused by the actual heart failure. So a TCC code may be caused by another problem in reality.
The first thing to do is to check the quality of the transmission fluid and see if it is nice and pink or if it is dark and has a bad odor. Use a white cloth or paper towel to do this. Meaning pulling out the transmission fluid dipstick to see what the fluid looks like on the distick. The next step is to lower the transmission pan and inspect it for contaminants such as clutch material in particular and perhaps brass shavings. Assuming the pan is relativly clean, only the mechanic looking at it can tell you this, perform a transmission maintenance with the correct transmission fluid for your car. This is critical, no cheating:… Every manufacturer has a fluid designed for their particular transmission. One that has the proper additives in it, to prevent a situation from occuring. The additives are called friction modifiers. A lot of shops cheat here, they buy conventional fluids and use additives they purchase that are supposed to enhance the ATF to meet the specs. That is B.S…
Note: Chrsler products have a very specialized fluid that is specifically designed to prevent these problems from happening. What I’m saying is use genuine Chrysler/Mopar ATF in a Chrysler/Mopar vehicle. We used to use Penziol synthectic Mopar ATF because Penzoil developed it in conjunction with Chrysler, therefore they are THE factory supplier of ATF to Chrysler. You can buy it in most parts stores. It is a very good fluid BTW.
After the ATF and automatic transmission filter is changed and the rest of the bad or incorrect fluid is flushed out, hook up the scan tool and go through the computer reset mode. Then go drive it for about 15 miles. It should not act up anymore if that was the problem. I want to make sure you understand that if the transmission fluid caused your problem then you are not maintaining your automatic transmission enough or someone put the wrong fluid in it.
If the problem still persists than you probably have a bad torque converter. And yes a new front seal, front pump bushing, pump gasket and pump o-ring should be put in the transmission if you replace the torque converter. More important now is that the transmsiion has to be removed to do this procedure and you have to be prepared for the worst case senario because if there is more damage to your transmission. Many reputable transmission shops will not just put a torque converter in your transmission without fixing the other problems. If that is the case than a good used transmission may be in your best interest. GotTransmissions.com has the most qualified selection of low mileage used transmissions than anyone else. Most of them come out of low mileage wrecked cars. All of the ones they sell are certified pre-tested and well guaranteed.
That being said, there are several more tests we should discuss before the transmssion is even removed. One of them I consider to be the most important is a CVI (clutch volume index) test which tells the mechanic a whole lot more about your Chrysler TorqueFlite 604 transmission (trade name). See the next post for more on CVI and the theory and function of a TF 604 auotomatic transmission.
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