Sudden downshift while slowing down


#1

I have had a few times when my 2013 Chevy Traverse LT suddenly jumped to a low gear while quickly slowing down, causing the RPMs to jump up to 4-5000 RPMs. It remains in that gear until I am practically stopped. Is this normal?


#2

define “quickly slowing down.” If you’re slamming on the brakes it might think you’re trying to avoid hitting something, so it downshifts to help you slow down even faster.


#3

No it is not normal. Did you just acquire this vehicle or have you had it sometime. The first question the mechanics on here will ask is have you checked the transmission fluids.


#4

@shadowfax One example is I almost missed an exit off of a freeway, so I had to slow down rapidly (brakes did not lock up, or come close to it), but I wouldn’t call it slamming on my brakes in the same way you would when trying to avoid rear-ending somebody…

@“VOLVO V70” I purchased the vehicle certified pre-owned about 1.5 years ago. It now has about 52,000 miles on it, and had just under about 26,000 when I first bought it. I have not checked the fluid, but will when I get home today.


#5

I have a theory that–like all theories–could prove to be right or could prove to be wrong.
I think that the OP’s vehicle has likely always downshifted under those circumstances, but he didn’t notice it because they were relatively “soft” downshifts.

However, when trans fluid drops to a lower than normal level, it is not unusual to experience “hard” downshifts.

As was already suggested, the OP needs to immediately check the level of his trans fluid, and if it is low, to replenish it with the correct spec Dexron fluid for that model (check the Owner’s Manual for details). And, if the trans fluid has never been changed, the OP should be aware that it is nearing the time when his vehicle will be due for its second trans fluid change. Has the fluid ever been changed?


#6

As @VDCdriver says check your transmission fluid. If it is OK what you are seeing is normal. On some cars/trucks with automatics, when you hit the brakes hard, the onboard computer senses this and will cause the tranny to downshift to assist the deceleration. The first time this happened to me I was driving a mid sized U Haul on the interstate at normal speed, came over a rise to see traffic backed up without a lot of room to stop, I hit the brakes hard, not enough to skid, but hard, and I noticed the tranny down shifted. I would have stopped in time without the downshift, but boy it was nice to have the added assist.


#7

@SteveCBT is correct. And if the transmission happens to have a “sport mode” and it’s engaged, the downshift can be pretty startling. I was recently tooling around in a new Acura and tried its sport-2 mode. The thing was downshifting almost to redline at every opportunity even under light braking, and with 9 gears there were a lot of opportunities.

@“VOLVO V70” One does not need to be a real mechanic to ask clarifying questions. I have nothing but respect for the real mechanics on here and almost always defer to their superior expertise, but having been wrenching on cars for the better part of 30 years now I have managed to pick up a few things, and one thing I’ve picked up on is that people don’t always give you all the information you need in order to make a proper diagnosis.


#8

@shadowfax-I meant no insults to anyone who gives serious advice but just meant that there are working mechanics here.


#9

I wonder if there’s anything about that function in the owners manual, under automatic transmission operation. Maybe take a look there. I’ve never had that happen on any automatic transmission vehicle I’ve driven. The problem I’ve had with modern cars, esp small cars, is more that the transmission is downshifting too much in an attempt to go faster, not slower. That’s really annoying. But I suppose such a thing as downshifting to go slower is possible, especially with newer auto-transmissions becoming more and more computer controlled. Like I say, maybe the owner’s manual has some germane comments on the subject.


#10

Sure the information is in the owner’s manual;

Automatic Engine Grade Braking
Automatic Engine Grade Braking assists when driving on a downhill
grade. It maintains vehicle speed by automatically implementing a shift
schedule that uses the engine and the transmission to slow the vehicle.
The system will automatically command downshifts to reduce
vehicle speed, until the brake pedal is no longer being pressed.
While in the Electronic Range Select (ERS) mode, grade braking
is deactivated, allowing the driver to select a range and limiting the
highest gear available. Grade braking is available for normal
driving and in Tow/Haul mode.

I don’t believe it is necessary to be on a grade for engine braking to occur at highway speeds.

I never ask my customers if they have checked their transmission fluid, they lack the experience to understand what they are looking at with respect to the temperature to level relationship. General Motors and most other manufactures advise to have the level checked by a professional.

It is not necessary to check the transmission fluid level.
A transmission fluid leak is the only reason for fluid loss. If a leak
occurs, take the vehicle to the dealer and have it repaired as soon
as possible.

The transmission fluid will not reach the end of the dipstick unless the
transmission is at operating temperature. If you need to check
the transmission fluid level, please take the vehicle to your dealer.


#11

A lot of great advice on here, thanks everyone!


#12
If you need to check the transmission fluid level, please take the vehicle to your dealer.

Dealerships could extend this idea and make even bigger profits. The dealerships should install overpiced gas pumps and put in the owners manual " Do not check your gas level. If you think your gas level is low, buy gas at the nearest dealership." … :wink:


#13

Do you think dealers are making big profits by checking fluid levels for customers?


#14

No. My guess though is there’s a business strategy involved. The bean counters at dealerships find they make higher profits from their shops when more customers bring their car in for service. B/c they’ll often find other stuff that needs to be done in the process. And if their shop does the job, they keep the profit that would otherwise go to a different shop. I’m not complaining about it, that’s the American way, make a profit however you can. But I do think there is a business strategy involved with servicing, just like there’s a business strategy involved with selling the cars.


#15

I believe the theory behind not having the transmission fluid check-able by mere mortals is to prevent said mere mortals from adding the wrong fluid or adding too much fluid, causing transmission problems that the manufacturer might have to eat, or at least result in dissatisfied customers.


#16

The manufacture is interested in preventing damage to the transmission by helpful people with good intentions, the owner’s manuals are not written that way to benefit the dealer. This is also why transmission dipsticks are becoming rare, transmissions last longer if owners can’t add extra fluid and additives.