TACOMA: '05 Auto tranny question...

[Jim Swantko]

I love my truck - but I've noticed that anytime I am coasting and lift my foot off the throttle - the truck downshifts. This would be great if I were towing something ... but it's sort of annoying.

Does anyone else notice this? I can imagine that Toyota probably designed the software in the tranny for more towing applications... but I sure wish I could disable it around town.

Just wondering if I'm the only one.

[jayotto4]

Originally Posted by Jim Swantko

I love my truck - but I've noticed that anytime I am coasting and lift my foot off the throttle - the truck downshifts. This would be great if I were towing something ... but it's sort of annoying.

Does anyone else notice this? I can imagine that Toyota probably designed the software in the tranny for more towing applications... but I sure wish I could disable it around town.

Just wondering if I'm the only one.

Yup it does seem to slow you down using the engine and tranny. I like it because of the fact I do tow with it. I guess the good thing is that you will not chew through so many brake pads!!

[j4x4ar3]

I tow as well. The 05 Tacoma has a "new" feature that has an additional engine braking feature. Check your owners manual. There are specific shift points and speeds you need to be under to "activate" the engine braking features. It does say though that if you're in overdrive that those features are supposed to be disabled. Pretty cool if you ask me. Keeps me off the brakes in traffic.

[TacoSalad]

I noticed that too and figured it was the 5 speed trannies electronic controls searching for the best gear for the best mpg.

[rivalred]

Yes, I also notice when I left off the GO Pedal it sorta backs off or "winding down". I do not mind it one bit, could keep people from getting too close when driving in heavy traffic.

[MERCULA]

Ive kinda noticed if Im goin down a hill ,, it just rolls , but if I tap the brakes
then it down shifts and holds it in that gear , I really like it , Learn to use it
and it will save us brakes ect . Am i making any sense ?

[Jim Swantko]

Mine doesn't work like that. If I'm coasting down a hill (say 35-40 mph) and I lift completely off the throttle it will downshift. Then I need to press the gas to get to where it would have rolled to had it not downshifted.

It annoys the hell out of me.

No WAY does this help save fuel. I'd rather buy new brake pads personally...

[matt30]

Originally Posted by Jim Swantko

Mine doesn't work like that. If I'm coasting down a hill (say 35-40 mph) and I lift completely off the throttle it will downshift. Then I need to press the gas to get to where it would have rolled to had it not downshifted.

It annoys the hell out of me.

No WAY does this help save fuel. I'd rather buy new brake pads personally...

Engine braking isn't going to use more fuel. Fuel and Air are proportional in an engine. It keeps the engine from burning too lean or too rich; most cars run a touch rich for safety which means fewer parts air to 1 part fuel. By pressing the gas pedal (opening the throttle) you are letting in more air so the fuel consumption will increase to keep the mixture stoich (done by the ecu & injectors). Injectors are only capable of injecting fuel at their set rating so for example in your stock car you might have around 330cc injectors. Those injectors can only inject 330cc of fuel per pulse (fuel isn't vacuumed out of them while decelerating). By injecting more fuel when the engine isn't taking in air to ignite the mixture you will flood the clyinders and go into hydrolock. This means the engine can't expel the liquid in the cylinders. Liquid won't compress like air so in some cases of hydrolock one piston will be on the upstroke following the power stroke of another cylinder. The unburned fuel in the upstroke piston won't compress and either force the head of the engine to separate or the rod to break.

If you engine brake you are simply making the engine spin to meet the speed of the wheels based on your selected gear. You aren't opening the throttle to let more air in so more fuel isn't needed. The reason you accelerate is because the air and fuel mix and explode forcing the cylinder through it's next stroke and the cycle continues. This force makes you go (sorry to sound elementary). If you took in more air and fuel beyond idle speed and ignited it based on engine rpm then you would accelerate pretty quickly when downshifting instead of slowing down. Downshifting without throttle (gas + air) causes resistance. The resistance makes you slow down. The oil still lubricates the internals to protect against thermal breakdown.

[Jim Swantko]

I beg to differ. If I can coast (where the engine is stoich) to where I want to stop vs having coasting 75% to the point I want to stop then have to press the gas in order to "really" get there - I've used more fuel.

[blazze2005]

Think about what your saying though, You were coasting which means you were probably going kinda slow and then you took your foot off the gas completely and the truck downshifted. The truck is doing exactly what you told it to do. Try not to take your foot all the way off the gas at once and just feather off it a liitle at a time you might not notice it as much then. I also think the engine break is a great feature for everyday driving situations because it's much safer and less on the brake system. It might just save us all alot of close calls on the roads if you know what I meen. It has saved me a trip to the body shop allready As far as the gas issue I could have drove back from North Carolina To New Jersey on it's first full tank of gas but I would never run it lower then a 1/4 tank but i think I would have made it! The trip was 500 miles 1 way. I think thats good for a big V-6. And I was on and off the gas plenty because I wanted to break the truck in slow varing my speeds trying not to stay the same speed for a long period of time. I love My Tacoma and it impresses me more every time I drive it But this is just my OpInIoN

[Jim Swantko]

Just because you lift your foot off the gas does NOT mean it should downshift. Now if you slow down AND you lift your foot off the gas - then yes it should downshift.

But I can be rolling downhill and lift my foot off the gas to stay at the speedlimit - then I downshift and slow drastically.... then I need to press the gas again to keep from getting hit from behind. It's annoying as hell to me.

[remelad]

I also hate the way the auto trans acts. If I wanted to slow down, I would use the brakes...I don't need the trans downshifting because it 'thinks' I want to slow down.

[ffproulx]

Ok, my new truck will be here at the end of the month and from what I am reading it sounds as if it acts similar to a jake brake. I drive big trucks almost every day at work. If you lift completely off the throttle, then the jake kicks in, if you are just touching the throttle, then you are not adding any fuel, but you are keeping the jake from engaging, basically coasting. That sounds very similar to what is happening. Try just keeping your foot barely on the throttle and see what happens. It is there for a safety and to help stop. It is a heavy truck to slow down. I will try and post again when my double cab comes in. thanks, hope this helps some.

[Jim Swantko]

Originally Posted by remelad

I also hate the way the auto trans acts. If I wanted to slow down, I would use the brakes...I don't need the trans downshifting because it 'thinks' I want to slow down.

Thank you!