[GolfTango]

This is for a 09 Aura 2.4 6AT. I know that the 6AT is plagued by complaints of its shifting behaviors and characteristics. I have had the BCM re-flashed by the dealer which helps in some shifting conditions.

But now I've noticed that in cold weather, or more importantly when the vehicle is cold, while accelerating the RPMs jump. This seems to stop when the vehicle is up to operating temp.

Basically, vehicle is going from 2nd to 3rd, RPMs about 3K, the engine revs up, RPMs jump to 3500 or so, then comes right back down. Same going from 3rd to 4th, RPMs at 3200 or so, then the engine revs to 3800, jumps right back down.

It is almost like the transmission is slipping. Any ideas? Or have any 2.4/6AT owners experienced this?

 

[jack0395]

I have a similar problem with mine. 2009 4cyl with 6AT. Mine only seems to happen between 3rd and 4th gear and only when the car is quite cold.

 

[jeepgrady]

I had a Silverado that did the same thing and it stated in the owners manual that it was normal in cold weather. It was designed to do that to warm up the tranny faster. I don't recall if it also states this in the Bu's manual.

 

[GolfTango]

I had a Silverado that did the same thing and it stated in the owners manual that it was normal in cold weather. It was designed to do that to warm up the tranny faster. I don't recall if it also states this in the Bu's manual.

Not sure what year Silverado you had, but this in the 09 manual:

When temperatures are very cold, the Allison
Transmission® and Hydra-Matic® 6-Speed transmission’s
gear shifting could be delayed providing more stable
shifts until the engine warms up. Shifts could be more
noticeable with a cold transmission. This difference in
shifting is normal.

Not really the same thing. The Aura manual makes no mention of cold shifting. Neither does the Malibu's.

 

[BillD64]

Based on the OP's post it sounds like the tranny is spending some time making the shift between gears and the engine is free to rev for that short instance. That could happen in a tranny that is cold and the shift valves are moving slower than when the oil is hot. I don't think the tranny is slipping. If it was slipping you would notice the rpms increasing without the speed increasing when there was no shift occuring.

Bill

 

[1LT]

This is for a 09 Aura 2.4 6AT. I know that the 6AT is plagued by complaints of its shifting behaviors and characteristics. I have had the BCM re-flashed by the dealer which helps in some shifting conditions.

But now I've noticed that in cold weather, or more importantly when the vehicle is cold, while accelerating the RPMs jump. This seems to stop when the vehicle is up to operating temp.

Basically, vehicle is going from 2nd to 3rd, RPMs about 3K, the engine revs up, RPMs jump to 3500 or so, then comes right back down. Same going from 3rd to 4th, RPMs at 3200 or so, then the engine revs to 3800, jumps right back down.

It is almost like the transmission is slipping. Any ideas? Or have any 2.4/6AT owners experienced this?

My 09 Malibu does the same exact thing when engine is cold... I'm pretty sure it's normal.

 

[GermWar]

Wells it's good to know that it's normal.

Damn got mad at my bu for nothing.
Now I gotta treat her to a bath.

 

[dpopeck]

Wells it's good to know that it's normal.

Damn got mad at my bu for nothing.

Not sure it's normal for you -- you live in sunny California.

Sorry, this winter weather on the East Coast is making me crazy.