Bad to downshift in auto?

That's what i figure. Buddy of mine who does not live here came to visit a few years ago and burned his brakes right off on that hill. Caught him by surprise. Brand new truck too. I told him, you got to shift down or you will be screwing your brakes up all the time. He kept going on about what kind of damn hill is 26 miles long ? Never seen anything like it before. Flat Lander.

The only warning it says is make sure you are off the gas when you shift down with the auto tranny.

 

Pretty much , we have "rolling hills" if you want to get technical.

On another note, I destroyed 2 transmissions in a Mazda I had many years ago, I swear it was due to down shifting it too much. The motor however ran like a sewing machine at 90k miles when I traded it in.

 

This is true , the rev limiter will keep the engine below the imminent damage threshold , but it would probably not be the best place to keep the revs at on a consistent basis , no ?

 

I down shift mainly while towing the boat down a mountain from the 7,000' elevation. The road has alot of sharp turns and down shifting helps keep me from having to constantly ride the brakes...that's the purpose of the lower gears (and to keep the tranny from searching while going uphill.) One thing I haven't seen mentioned is constantly downshifting with the automatic while wheeling in 4WD. Is doing this (mainly while going uphill) hard on the tranny and taking a chance of it overheating? I know when in 4HI downshifting would be preferrable if the tranny is hunting, but what about when your in 4LO?

 

You sure?

The rev limiter will interrupt spark (or fuel), but if the vehicle is still in gear and rolling, won't all internal parts will still be moving?

Correct?

 

You want to prevent hunting cause it causes so much heat to build up so I'd be just shifting to prevent that regardless what mode I was in.

 

Don't lump me in with those tards. They seem to forget that we have the A340 Transmission that was made for the Tundra and it's 4.7L V8.

Brake pads may be cheaper but the transmission is stronger...

 

I don't think it would matter, in this case the transmission would still be the same reguardless of the transfer case. There have been many situations when wheeling where I have stayed in 4L and 2nd for long periods.

 

I've bounced off my revlimiter on all my bikes with never a problem. On one I lost count 50k miles ago.

I've down shifter several vehicles close to redline with never a problem (that is more dangerous). The only time I thought I caused damage was when the tranny started to whine quite loud. Best I could tell was one of the shafts in the tranny got spinning was pass design limits -- still kept going like nothing happened

 

^ Thats how it should be. On flat ground D is fine but there are those cases when I need to be in charge, after all I am the one that can see what is coming up.

 

I downshift all the time. Where we go riding (Dirt bikes) it's up hill or down hill. So downshifting is the best way to control the speed. I do it on all my cars.
Hell it's a Toyota!

 

Really? I've read that in other places, but mine sure as hell doesn't downshift on it's own while going downhill. If I don't downshift manually, it just coasts like it was in neutral and by the time I get the 1/3 of a mile down my residential hill I'm doing 50. I WISH it engine braked on it's own but no dice. That being said I have no problem manually downshifting. That's what it's there for, right?

 

Good post.

You can downshift with the auto tranny. Engineers do think of these things.

Only should really need to do it when dealing with large hills/mountains and such things where all riding your brakes is going to do is boil the brake fluid and/or cause excessive heat, both lead to brake failure.

 

Yeah, to clarify this point, rev limiters only work when throttle is applied. If you are coasting down a hill, the engine is being 'driven' and there is nothing that is going step in and keep you from over red line. This can cause a lot of damage and automakers are pretty savvy to it. I work with an engineer who used to work at the Porsche engine group. They used to void warranties on cars that have been taken to track days and over reved on down shift. The ECU would track number of engine cycles that the engine spent over reved.

With this said though, engine braking with an auto is fine on big hills and long grades. Just choose the right gear that is going to spin a safe rpm and apply the brakes as required to maintain a safe rpm.....

 

^ you know this is actually something I learned here. I didn't realize that the rev limiter wouldn't stop a coasting engine. Luckily I have always used a combo of gears and brakes to keep the rpm below the red-line. I haven't owned many vehicles that actually had rev limiters. Used to have to install them with my 6AL boxes.

 

I have blown gaskets and seals down shifting an auto transmission. I have bent valves down shifting a manual. A lot had to do with my age and Hot roddin' around many years ago.

Rev Limiters don't always work, and extra pressure in the transmission has to escape some how. Lets just say I have learned my lessons the expensive way.