Corolla down-shifts when braking downhill

2006 Corolla, when it's downhill and I press the brake pedal above a certain braking power, it shifts down the transmission. I was trying to figure out if that's a feature of the transmission and how does it know that the car is travelling downhill. It's probably intended for adding engine braking but sometimes it's just annoying since revs go up and it strains the engine and transmission. BTW, no down shifting when braking on a level road.
Reply to
Dan
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it's supposed to.

yes it is. it helps reduce brake load, thus premature wear, and in extreme cases, brake overheating.

brakes are on, throttle is closed and speed is maintained above a certain level.

rubbish. any load from engine braking is well within the capabilities of both engine and transmission and lower than when the gas pedal is down.

Reply to
jim beam

Dan wrote in news:b2648f19-54f7-4d7e-b8e2- snipped-for-privacy@r27g2000yqb.googlegroups.com:

Well if you slow down, the car will shift to a lower gear. You *do* realize that don't you?

How many speeds in your automatic transmission? That certainly will have an effect as well.

As for "straining" he transmission and engine, just how many RPM are you getting up to when this happens?

Reply to
chuckcar

And this is a shame. Toyota salesmaen (most of them) used to really know the product and could answer the questions. Now, they're *just* salesman and would be selling Fuller brushes if they weren't selling Toyotas...

Reply to
Hachiroku $B%O%A%m%/(B

It should be freewheeling. The only time it should downshift is when the rpms and the speed gets below a certain level, and I'm not sure what that would be for your car. It seems you should be going fairly slow before the trans downshifts.

I would have the operation of the trans ECU checked.

Reply to
Hachiroku $B%O%A%m%/(B

I have never heard of any normal car doing that. There are no level sensors that I have ever heard of. Most cars down shift according to rpm and speed. But it is at slow speeds. Like under 20 mph. Is your trans fluid level normal? Screen clean?

Reply to
Paul

It's called "grade logic control." Sometimes "grade logic system (GLS)" Below is a Honda description. Looks like they tout it more than Toyota, and have used it longer. Standard on autos since 1997. Here's a Toyota reviewer reference to it for the 2005 Camry.

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"Perhaps the most important upgrade is to four-cylinder models - a new five-speed automatic transmission with electronic grade logic control replaces the old four speed, for improvements in both performance and economy."

Looks like your Corolla got a version the next year. Personally, I like making the shift choice myself. There's a big honking shift lever for that. I would also find that Corolla shifting annoying. My GM car freewheels down long, steep grades, exceeding the cruise speed setting. A little braking takes care of that and the trans never shifts. Fine with me, since I'm hardly ever on those grades. But a case can be made for its usefulness to downshift while in cruise control. Some who often drive grades often might like grade logic to keep cruise control working. You might make a case for using it on heavier vehicles which tow, as a safety feature. And when you think about it, a properly and quickly working system should reduce braking distances in emergency stops done when in 2nd gear or higher on any car.

But I like having the choice whether to use brakes or a lower gear to maintain speed. You should complain to Toyota. At least they could put a disable function on the nanny shifting for those who find it annoying or worse, or refine it somehow. There are plenty of complaints about it, and some who like it. Others start out not liking it, but quickly adjust to it. Like all complexity added to control systems, errors occur. Excessive engine braking while approaching a stoplight is one complaint that is too common. Here's a few Honda complaints, probably caused by bad programming or sensors.

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smission

*********************************************************************** Grade Logic Control To reduce gear "hunting" and unnecessary shifting, Grade Logic Control and Shift Hold Control systems are integrated into the shift programming of Accord automatic transmissions. Grade Logic Control alters the 5- speed automatic's shift schedule, reducing shift frequency while traveling uphill or downhill. Using inputs monitoring throttle position, vehicle speed and acceleration/deceleration, Grade Logic compares the operating parameters with a digital map stored in the transmission computer. When the system determines the Accord is on a hill, the shift schedule is adjusted to automatically hold the transmission in a lower gear for better climbing power or increased downhill engine braking.
Reply to
Bob Cooper

In message , Hachiroku $B%O%A%m%/(B writes

I don't know about the US, but I'm pretty sure that free-wheeling is unlawful in the UK. You'd certainly fail your driving test if you selected neutral before coming to a stand and engaging the hand brake.

Reply to
Clive

Not frewheeling that way, but the clutch packs allow the transmission to spin more freely until certain revs are attained, and then the car downshifts.

If you're doing 50MPH down a hill, the trans should stay in the highest gear.

Reply to
Hachiroku $B%O%A%m%/(B

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