Transmission drops when I let go then rev up?

1999 DODGE DURANGO
109,000 MILES • 5.2L • V8 • 4WD • AUTOMATIC
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SCAPPS31
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Hits 3,000 RPMs when taking off then drops when I let go then rev up then pulls hard. The engine light came on couple days before it happened, then it went off and still isn't on, but it won't go. changed the neutral sensor, and no filter is clogged, and transmission fluid is good and full, but my husband put in a new muffler and since then it has been using so much gas.
Oct 12, 2024 at 5:29 PM
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STRAILER
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These problems might be related, we need to run the codes to see which ones are stored.

This guide will help:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If the exhaust is partially clogged it will cause the transmission to act strange. Please go over this guide and get back to us.
Oct 13, 2024 at 3:55 AM
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SCAPPS31
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We took it to get codes, and none showed up even though the engine light came in but then went away.
Oct 13, 2024 at 11:21 AM
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STRAILER
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When the engine light comes on it should have codes unless the engine control module is going bad. To me it sounds more like the transmission is going out. Do you know if the scan that was done was a CAN scan? If not let's try this next. Did the problem happen right after the new muffler, or did it take a while? You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

Please go over this guide and get back to us.

Oct 14, 2024 at 3:15 AM
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SCAPPS31
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I'm not sure we got it scanned at Oreilly's and it took a couple of weeks after the new muffler we thought it was one of the speed sensors, so we changed the input speed sensor and it's still not shifting.
Oct 14, 2024 at 4:32 AM
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STRAILER
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If there are no codes and the fluid looks good a sprag or something must have broken inside the transmission.
Oct 15, 2024 at 1:53 AM
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