High Revs downhill. Normal?

I never go out that way, but I notice it all the time going down Kirchner Rd.

 

It's called engine braking and is a good feature for preventing brakes from overheating. GM even advertises this feature on its Allison transmissions for the HD pickups. The drivetrain is designed for it. And it isn't stressful on the engine since it's just pumping air (fuel injectors turn off when you lift the throttle).

 

Mine only does this on hills if I am applying brakes unevenly, I think it's programmed to sense downhill and brake pressure. If I ride the brakes the whole way down the hill it will not kick it, but if I let is speed up then touch the brakes to slow if down 10ish MPH it will kick in, especially if I touch the brakes more than once and it continues to gain speed. I also think the situations have to be right for the gear change or it won't do it.

My grandfather's take, who worked on planes in the air force for years and then cars for 35+ years, was "brake pads are cheaper than drive train components, ride the brakes"

 

Your life is worth more than the drive train components, don't ride your brakes. Once they overheat they're useless. Granted it would take quite a long distance of riding them to cause a failure, but some (most?) people just are not very smart and thus we have these nannys.

If you know what you're doing it's a judgment call. If you are not sure then just let the truck work the way it's designed. Higher RPMS does not equal more drive train wear, that's a misconception.

 

I don't agree with his take, just thought it was funny.

However, unless your towing something or descending some pretty intense mountain passes I don't think you could overheat the brakes on these trucks. I travel steep mountain passes regularly, western WA, with a few hundred pounds of weight in the back and 4 people inside, they're not over heating. My first pads lasted 100k miles...

 

You are probably right, I have not tried it to find out....but we all know what would happen. A nice family pulling a trailer overheats the brakes and crashes. Lawsuit Toyota. Just like people don't know how to switch to neutral or turn off the key, they don't know to use a lower gear either.

 

No.

 

It 's the price you pay for having drum brakes on the rear.

 

^Not sure how drums come into the discussion. 70% of the braking is done in the front.

Not an electronic nanny. It's actually considered a feature. Drivetrain stress from engine braking is negligible.

 

I'm not sure where drum brakes come into this at all.

 

A few people are obsessed that tacomas don't have rear discs.

 

and what the hell does that have to do with grade shifting?

the tacoma has better stopping distance than colorado and colorado has discs

 

I could be wrong but I'm pretty sure the Tacoma isn't using engine braking, it's only downshifting which is entirely different.

 

In this case you are wrong.

 

yep

 

When you downshift and let off the gas, the wheels try to turn faster than the engine. Since the throttle body butterfly is closed, the engine compresses air and generates heat (which is easily dissipated by the engine's cooling system). This way, the vehicle's kinetic energy is converted to heat. This is engine braking.

Diesel engines traditionally don't have a throttle body butterfly, so they need add-on devices to accomplish the same function, hence the need for a cockpit switch. Big haul trucks have jake brakes that move the exhaust valves. New pickup diesel engines have an exhaust brake that chokes exhaust flow, either with a valve in the exhaust pipe or by moving the turbo vanes. In Costa Rica, I drove a Land Cruiser Prado diesel with neither feature, and indeed downshifting did nothing to slow the vehicle down!

 

not sure you got the joke

 

Why else would the transmission downshift going down hill ? Just put your cruise on in a hilly area and watch it down shift for braking as needed. It seemed obvious the first time we drove it. Wife's Venza operates the same way. Don't most newer cars and trucks do it ?

 

Thank you for blowing my mind bud

 

Humor me.