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Cruze 6Spd AT Downshifts and gets stuck at 5th gear

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5th 6spd auto cruze downshifts gear stuck transmission
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plankton

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Discussion starter · #1 ·
Hi,

Ive encountered a strange problem with my cruze over the past few weeks and was hoping someone could help me with it before I go back to the Service Center/dealer.

Heres my problem : While cruising at around 120km/h on the highway, the car suddenly downshifts to 5th. Trying to manually upshift the gear doesnt work as in the gear number still shows 5th, and the RPM increases like it is in a lower gear. Usually I lower my speed to around 80/90 to match the 5th gear and find a place to stop. On each occasion, stopping the car and turning off the engine for around 5 minutes before driving again solves the problem, and the gears shift properly up/down to/from 6th.

On one occasion the Check Engine Light lit up, and after going to the service center, the error code returned was "P0625 Generator Field F Terminal Circuit Low". The service center proceeded with an alternator change, but unfortunately that did not solve the problem as it happened again. For the other times it happened, no check engine light or DIC error occured :(

Ive noticed that this problem occurs after driving a while (~80KMs) and then hitting the highway at those speeds. Short trips (~40KM) with speeds reaching 120-130KM/h does not seem to trigger it. Has happened both during the day (~35 degrees Celc) and night. Does not seem to happen during long trips where the speeds dont exceed 90KM/h (city).

Some extra details:
- 1.8L Cruze, 6spd AT
- Battery/Car is 1yr old, During the diagnostic check, the battery passes the check (but this could be because the battery got charged while driving to the Service Center? )
- Stock Car, no modifications

Could it be the that the battery is not able to provide the needed current/voltage at those speeds and temperature and needs to be changed? I have done quite a few long drives (600KM) after buying the car and did not get this problem.

*Im getting an OBD2 bluetooth to run with torque, going to try and log the car readings and Voltage levels (hopefully)

Thanks for the help
 
#2 ·
The car will try to downshift to lower speed if you start getting crazy while not on gas pedal, or if cruise is engaged and you exceed the cruise speed by quite a bit.... What you have going on is.... Well, wrong! I would have them service it. No trifecta tune eh? If so maybe a TCM wipe using the red trifecta cable might do SOMETHING but... I would let the pros handle this one.


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Discussion starter · #3 ·
hmm. my car doesnt have trifecta tune/cruise control, and when it happens, im only maintaining my speed around 120km/h with no sudden changes in throttle. Could it be related to heat? wierd thing is after I turn off my car and resting for a few mins, it works fine o_O . The 'Pros' didnt seem to be able to find the problem after sending it there 3 times, thought I'd get more input from here before going again. thx!
 
#4 ·
the battery is only used to start the car, all systems while driving the car are ran through the alternator . i dont understand why the service centre is trying to change your alternator... its your transmission that has a problem lol! i think you may have a problem with your tcm,id get it reflashed by chevy to see if that solves it.
 
#5 ·
This is a transmission control issue - not alternator. My guess it's heat related. Call GM and open a ticket with them. Also, since your dealership isn't willing to look at the transmission I would try a different dealership.
 
#9 ·
LarryF said:
I'm having the same problem exactly - not including the Check Engine Light coming on, just the 5th gear problem. Did you ever resolve it?
Thanks!
Click to expand...
Any issue(except electronics)with the transmission should be covered under the powertrain warranty(5year/100K miles).

Without more info it would be difficult to diagnose or help at all. Say the automatic drops from 6th to 5th on a slight hill grade, it will remain in 5th until the load decreases(you crest the hill). Wonder if this is what your seeing? Noticed the OP says he couldn't even manually shift it to 6th with is car and has a code present.
 
#10 ·
While the problem may seem to be a transmission issue, keep in mind that it's under the control of the computer. I wouldn't ignore the alternator code. It's possible (and I'm taking a wild guess here) that if the alternator output is sensed as low, the car may downshift to give the alternator more RPMs. Given the known issue with battery cable, it wouldn't hurt to point that out to the dealer. It wouldn't hurt to monitor the system voltage at that time.
 
#11 ·
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plankton,

Have you made any progress in getting your transmission issues fixed?

I own a 2014 Cruze 1LT and the 6T40 automatic and it has behaved badly since Day One. Spoils the entire Cruze driving experience and I literally hate the car. I've taken the car to a couple Chevrolet dealerships for troubleshooting and repairs only to be told by their respective service managers that their evaluation and GM Chevrolet's diagnostic software tells them the car's all good and there is nothing can be done.

Horse manure. The car drives like crap. The one service manager appeared not to understand the problems at all and said he'd research them, of course he never did. And the other service manager told me he agrees the transmission's performance is miserable but he cannot repair what Chevrolet tells him isn't broken.

Good luck getting it fixed, because I've had none.
 
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#12 ·
UlyssesSG said:
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plankton,

Have you made any progress in getting your transmission issues fixed?

I own a 2014 Cruze 1LT and the 6T40 automatic and it has behaved badly since Day One. Spoils the entire Cruze driving experience and I literally hate the car. I've taken the car to a couple Chevrolet dealerships for troubleshooting and repairs only to be told by their respective service managers that their evaluation and GM Chevrolet's diagnostic software tells them the car's all good and there is nothing can be done.

Horse manure. The car drives like crap. The one service manager appeared not to understand the problems at all and said he'd research them, of course he never did. And the other service manager told me he agrees the transmission's performance is miserable but he cannot repair what Chevrolet tells him isn't broken.

Good luck getting it fixed, because I've had none.
Click to expand...
OK.....your post has me interested.

A few questions.....current mileage.....any modifications......if modified (such as reprogramming for example) how many miles had the car accrued prior to the install.

Gotta start somewhere, right?

Rob
 
#13 ·
Hay robbie whom are ya writing to Horsemanure or Plankton ?
 
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