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Old 05-06-2012, 10:48 AM
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Angry Torque Converter / Transmission issues.

I've driven my Jeep just over 1,000 miles since I bought it two weeks ago and everything has been just peachy until this morning on my way home from Knoxville to Atlanta. I noticed the transmission / torque converter was not staying locked in overdrive. When locked in 5th @ 75mph RPMs are ~2100. Every few seconds I can feel the converter unlock and the RPMs jump to ~2400 and then finally go back down when it locks up again. Really annoying. Hoping I don't have to replace the torque converter but I'm beginning to get that feeling. No lights came on during this 3 hour trip and the torque converter was locking and unlocking the entire way. Under heavy load (foot well into the throttle) it seems to stay locked up just fine. See video:

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Old 05-06-2012, 12:51 PM
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Re: Torque Converter / Transmission issues.

Updated: I disconnected the battery and let the car sit for 15+ minutes and went for a test drive. This definitely helped. I only noticed it unlock one time on a 45 minute drive. I'm hoping its an electrical issue and not the converter... but im not totally convinced yet. Anyone have some input here? TCM ?
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Old 05-06-2012, 04:22 PM
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Re: Torque Converter / Transmission issues.

There are nowadays many electrical inputs to the PCM and TCM for the control of the transmission. It could be a problem with a transmission speed sensor or TPS sensor, but that is a wild guess at this moment. If you have a scanner which shows live data, you could monitor the TPS and see if its steady or fluctuating at the times the unlocking happens.
The first things i always do when electrical gremlins pop up, is checking/cleaning the connectors of PCM, TCM and especially the transmission speed sensors, since they are placed in a harsh environment.
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Old 05-07-2012, 02:27 AM
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Re: Torque Converter / Transmission issues.

Quote:
Originally Posted by Frango100 View Post
There are nowadays many electrical inputs to the PCM and TCM for the control of the transmission. It could be a problem with a transmission speed sensor or TPS sensor, but that is a wild guess at this moment. If you have a scanner which shows live data, you could monitor the TPS and see if its steady or fluctuating at the times the unlocking happens.
The first things i always do when electrical gremlins pop up, is checking/cleaning the connectors of PCM, TCM and especially the transmission speed sensors, since they are placed in a harsh environment.

Good call with the TPS... VERY common problem on the 4.7l and if the computer is seeing wrong TPS signals it can tell the transmission to do weird things (without throwing a code because its doing what its told). The TPS when it fails more often than not doesnt throw a code (unless it throws an injector fault, weird I know). Great suggestion frango!

Do you ever notice your idle fluctuate? it should be rock solid, if it wonders around a bit even further indication of a faulty tps.
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Old 05-07-2012, 03:13 PM
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Re: Torque Converter / Transmission issues.

I'll have to check the TPS tonight. My K&N CAI should have been delivered today. So while I'm in there I'll just go ahead and replace the TPS also. I had noticed a semi-rough idle. RPMs bouncing around 600-700.
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Old 05-07-2012, 07:56 PM
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Re: Torque Converter / Transmission issues.

yep that is an indication of a failing tps (not that it is 100% the failure)
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Old 05-07-2012, 09:14 PM
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Definitely sounds like tps to me.


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Old 05-08-2012, 12:11 AM
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Re: Torque Converter / Transmission issues.

Thanks for the input guys. Replaced the TPS tonight. Went for a little test drive and had no issues. Only time will tell now. Also put the CAI on and SuperChips 87 tune into the computer.
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