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Discussion Starter #1
Hi everyone.

Yesterday i went for a drive and my CEL came on. i got a P0700 and a P0740. I looked those up and see that p0740 is the torque converter failing to lock up.
I cleared the codes to see if they will come back.
Today i drove around to see if the TC would lock up or not - it will not. usually i can get it to go in 4th @ a little over 40mph. 55mph and 65mph same thing - it will not lock up.

So what can i do/check? My gas mileage is horrible since it is running at higher rpms. Im not too worried about the transmission getting fried from heat since it is very cold out but i still wonder what to do.

I can't afford a new/rebuilt transmission right now - i know i want to get one or overhaul mine sometime being that the car is close to hitting 180,000 miles.

Its a 2001 LHS. 42LE transmission
Thanks!
Josh
 

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So, is it going into 4th without lockup? If so, RPMs will only be about 200 higher than normal, which will hardly affect your gas mileage. Or are you saying it won't even go into 4th?

Since neither 4th nor lockup will engage if the coolant or the trans fluid is really cold, it could just be the weather if you're in an extreme climate. Or a sensor could be bad, or its electrical connection. On my truck, 4th will not engage until the coolant reaches 60F, and lockup won't engage until the coolant reaches 140F. The latter can take 3-4 miles of driving in winter. And occasionally if the truck has sat for a month, it still won't engage for several miles after that, until I shut down and restart.
 

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It probably is time for overhaul kit and reman converter. The TCM won't set P0740 if the coolant or ATF are under the allowed lock-up temperature, so there is likely an internal leakage/wear problem.
 

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First common place to start is checking the fluid, then from there you may want to see how best you can get the car hooked up to a scanner that can better see what is working and not working, that is the sure way to go if your fluid is fine. I have rarely seen 42LE's fail unless the run to low on fluid from the cooler lines leaking. These transmissions are very strong, don't confuse them with the older electronic transmissions that came in earlier Chrysler products, there are some similarities but they are not the same.

If the shop tells you that you need a rebuild then have them tell you why and to read you the CVI's, and explain what the failure is, don't let them convince you it is internal with no proof, it is just them trying to use the reputation of Chryslers old transmissions to sell you into a rebuild which is unacceptable.

It's hard to say without being there to diagnose it, if you lived in Illinois I could help you better but I think it is pointless to start throwing in parts without knowing the cause and unfortunately you need a scanner and have to simulate a road test and see what is working and not working to determine what it is and I can assure you this is not common.
 

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Discussion Starter #5
Just wanted to update everyone on what i found out about the torque converter. I was looking at diagnostic procedures for the P0740 and i came up to the last step where it could be the valve body etc, and it said in either case replace the torque converter. So on a strong suspicion that the TC went bad i had a shop replace it for me. (every shop told me that it probably wouldn't fix the problem, and some said they would only replace/rebuild the transmission and not just replace the tc.)

After i got the car back the shop had found granules in the transmission filter (it was not plugged) so they flushed the cooler and transmission. It is now good to go.

it goes into lockup every time that it should without issue. Today i cut open the tc and had a look inside and the clutch definitely failed. good thing i got it in time before more problems were made.

Thanks for everyones help!
 

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Sounds like that was close, and sad to say a lot of shops will tell you this as they dont want the liability hassle if they replace the torque converter and things go south or it doesn't improve the situation. Sometimes persistance pays as you can see here.
 
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