Skip the auto shop - Our mechanics make house calls

Q: Auto transmission downshifting to lower gear when decelerating causes the car to lurch. Why?

asked by on

When decelerating through 20 mph the auto transmission downshifts to a lower gear than needed causing the car to lurch like hitting the brakes suddenly. I feels likes downshifting into 1st gear at 20 mph when it should be downshifting into 2nd or 3rd gear.

My car has 115000 miles.
My car has an automatic transmission.

This may be a result of low transmission fluid or potentially a faulty transmission control module. A faulty transmission control module may cause a delay in acceleration or erratic shifting of gears. The transmission control module has various sensors such as vehicle speed sensors, wheel speed sensors, throttle position sensors, turbine speed sensor, and transmission fluid temperature sensors that all direct information to it in order for it to perform it’s function. Other components controlled by the TCM are components such as a kick down switch, traction control system, and cruise control module. Any of these may also affect the way the transmission control module performs and controls the transmission and the shifting of your vehicle. In your case it sounds like you may have a faulty kick down switch causing the transmission to downshift prematurely. I would suggest having a professional from Your Mechanic come to your location to properly diagnose your transmission shifting problem.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Auto transmission downshifting to lower gear when decelerating causes the car to lurch. Why?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: TMPS/PS Light

Hello, and thank you for writing in. The power steering system, TPMS system, and the stability control are all connected. The problems do likely coincide. To start, consider any changes the TPMS system could have gone through (change of tires,...

Q: Backed up the drive way then put it in drive while stopped gave gas the car made a sound then it wouldn't go anywhere 2007 Honda Accord

Hi there - I suspect you have sheared off either the CV joint, or the axle shaft on the front side that was spinning on the ice. When the tire went from spinning freely (under power) to a full stop...

Q: Noise Comes Out From My Engine

Hi there. Our mobile mechanics are really good at diagnosing the problem first, before any repairs are made. We actually recommend having one of our mechanics come to your location and complete a car is making a noise inspection first....

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...