Transmission shift from high gear

TDS5888

MEMBER
2003 DODGE NEON
2.0L
4 CYL
FWD
AUTOMATIC
168,000 MILES

Transmission will sporadically downshift when in high (fourth) gear, momentarily, with or without cruise control. No check engine light comes on. I added some K&W Trans-X slip-stop which helped sluggish shifting but did nothing for downshift problem. Rpm's do not jump too much while this happens.

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,512 POSTS

Does the car seem to have low power as well? I am thinking the catalytic converter might be partially plugged causing the vacuum to be low which will make the transmission shift the way it does.

Here is a guide to confirm the problem:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please let me know.

Cheer, Ken

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Wednesday, February 24th, 2021 AT 2:17 PM

TDS5888

MEMBER
7 POSTS

I saw that Neodeac had the same problem on his 2002 Neon in March of 08 and the only answer I saw was to check fluid level and maybe do a tranny tuneup and add atf+4 if needed. I did a vacuum leak test with isopropyl alcohol and found no issues. Plenty of power and shifts strong, idles good. Haven't tested catalytic converter yet. My car has about 180000 miles on it so probably needs a tuneup. It jumps out of overdrive and revs a few hundred RPMs but goes back to overdrive almost immediately.

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Wednesday, February 24th, 2021 AT 2:17 PM

KEN L

MASTER CERTIFIED MECHANIC
47,512 POSTS

I would do the tune up first and then check the cat just to be safe.

Here is a guide to help you.

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Please let us know what happens.

Cheers, Ken

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Wednesday, February 24th, 2021 AT 2:17 PM

TDS5888

MEMBER
7 POSTS

My car doesn't need an engine tuneup, it runs fine. I'm talking about the tranny might need it. Thanks

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Wednesday, February 24th, 2021 AT 2:17 PM

KEN L

MASTER CERTIFIED MECHANIC
47,512 POSTS

"My car has about 180000 miles on it so probably needs a tuneup." I like to make sure the car is up on its service so we don't chase your tail this is why I suggested it.

It is starting to sound like a shaft speed sensor can be causing the problem. When these go out they may or may not trigger a check engine light.

Here are there locations (below)

Please let us know what happens.

Cheers, Ken

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