Bad to downshift in auto?

Auto trannys run on hydrolic pressure.[/quote]

When stuff gets hot, pressure builds, I blew out the seals on a turbo-hydromatic 400 (which was considered bullet proof in its time) from hotrodding around and down shifting "For fun". At age 17 and minimum wage, that was an expensive lesson.

It only takes a tiny smack into a valve to bend it. A floating valve getting hit by a piston will do enough damage to cause compression loss. When trying to stop 3000-5000lbs cars with compression, floating valves can result in mechanical damage.

For fun lets say the following happens.

You are attempting to pass another car and are getting close to the red line. Suddenly you see another car jumps in your lane. Your reaction is to down shift before stepping on the breaks.

When that happens and your already close to red line, the sudden down shift will cause the engine to over rev beyond a computers control, and into mechanical collision between pistons and valves.

at age 19, this costs me 2500 bucks to have the heads removed on a 396 big block and have a complete valve job done.

around age 23 this costs me 2000 bucks to have the same thing done on 1200cc harley engine.

I am not advocating either way, just pointing out what it has cost me over the years, and why I prefer not to downshift an automatic.

 

I didn't read all the responses here but I can tell you this much. My friend has a Ford Windstar. He down shifts at every stop light, hill and stop sign to "save on gas". His van has 60,000 miles and he just spent $3500 for a transmission. Maybe downshifting didn't totally cause it to go out but it couldn't have helped it either. (You should feel how the van lurches and clanks and groans when he downshifts)

 

Ya but that is like a Ford. A model known for transmission problems. So what is your point ? This is a Tacoma forum. Last I looked it's a completely different transmission.

 

I would say it isnt a bad thing to do provided you do not overheat your transmission, if you are towing through the mountains you might want to be careful but im fairly certain you will be fine

 

I see what you are saying and agree with it on all the examples you have given but that is an entirely different beast. Apples to Oranges. It sounds like you were driving like a 19yr old, being close to red-line and down shifting. Of course if you are trying to break the trans you could do so on your truck too but if you do it properly there won't be an issue. My Th400 on my 72 chevelle is doing just fine and has only had minor maintenance done to it.

 

Point being that most automatic transmissions are built to operate in a similar manner weather it is a front drive mini van or a pickup. This is what happened to my friend. I know how he drives the van and the money he spent fixing it. That is my OPONION/point. After all, that is what the OP was asking for...correct?

 

That tranny failure on the ford van is related to something totally different. Don't have anything to do with shifting down.

I'm pretty sure the OP was asking about his Taco.

Kind of like do you worry about sudden acceleration on a Ford? It's pointless to try to put everything in one big bag and say well if it happened here well it will also happen there. The other one is there is no history of such problem on the automatic Taco. If there was there would be tons of threads here discussing it.

 

I doubt it would hurt it. If I owned an auto though, I'd probably only do it to control your speed on a steep decline. For day to day driving, I don't see the point. Why buy an auto if you want to drive it like a manual?

 

FWIW, my wife's 07 Rav4 downshifted on it's own one day on me. Had the CC set around 60, going down a hill speed climbed to between 65 and 70, and then the tranny downshifted to slow down.

So I'm gonna say if Toyota programmed the computer to do just that, then it's ok. lol It actually kind of surprised and impressed me at the same time. The fact that it DID that, and the fact they engineered that feature instead of just letting it free wheel and rely on the driver to brake.

With the Taco I downshift as needed with the manual. Up and down lots of mountains and valleys on the way to work, many with a stop sign at the bottom or sharp curves. Then again, I'm also downshifting so I have the torque when it's time to accelerate again. Will probably see if I need to downshift the Rav come winter time and snow covered roads.

 

I find it ironic how "now" everyone condones down shifting in an automatic, but just a couple of weeks ago a forum member got his nads pinched for down shifting a manual?

Weird...

 

Perhaps we should all mod over to a belt drive transmission ....... .

 

Slamming an auto down a gear in a panic situation or close to redline or shifting an auto like it is a stick is a little outside what is the norm and what I would consider abuse. Downshifting an auto down long grades is perfectly safe and isn't going to hurt a damn thing. I am wondering why so many worry about redline. In general you get really good engine braking much lower in the RPM range then redline. No need to run it so high. I find that I get really good engine braking aroun 3000-3500rpm. When the revs start to really get up there to like 4000rpm, I apply the brakes to get the rpm back down. This is a perfectly safe practice and is actually outlined in the Toyota owners manual. Abuse will eventually kill an mechanical device

 

Cause I didn't have time to wait for the right trans being that I was out of a car since the dodge blew up....but the auto doesn't bother me. And thanks for all the info guys.

 

Ok common sense guys! Obviously descending long relatively steep grades downshifting is a necessity to avoid boiling brake fluid, warping rotors and welding calipers. But for everyday slowing down and stopping downshifting just to feel like your doing something or because you have shifter envy and your wanna hear your motor purr just doesn't make sense.

 

*987277626771019

Exactly!

 

Yep, that's what the lower gears in the automatic transmission were designed for...engine braking down steep desents to keep you from having to constantly ride the brakes.

 

Because you're not slipping your clutch any more than usual down shifting in a manual. There are a lot more clutches in an auto transmission and its the second most expensive component in the car and a fairly fragile one. I'd never do it unless I was going down a steep grade with a trailer (or the need to go slow) for a long time.

A properly driven automatic will go through brakes 2-3 times more often than a properly driven manual transmission. That's life. Buy a stick and either put down the coffee when you're smoking the cigarette. No offense to the truly handicapped.

 

Wow guys thanks for all the info, it's actually going to be a single axle 6X10 enclosed Trailer so its not to big, and I've replaced my font rotors with drilled ones so it should help in the braking .

 

If you have no fuel going to the engine explain how it produces heat??

I know I am reviving a dead thread.. But I am curious..