RPM's dive when letting of gas

I was hoping to get some input on something I have noticed about my 06 tacoma V6 automatic transmission. If I am driving down the road and have to let off the gas, just before the transmission wants to shift into the next gear, the rpms will drop way down and then bounce back up. It only seems to do it if I let off the gas just before it wants to shift. If anyone knows anything about this and if it is normal or not, please let me know.

 

So you let off the gas before it up shifts which causes the RPMs to drop? Sounds like a normal auto trans to me. Maybe I'm missing something.

 

You sure you're not letting off the gas after it shifts into a higher gear , therefore rpms drop?

 

No it doesn't shift and the rpms drop really fast all the way down to as if it were idling or even lower and then they bounce up and then bounce a little more before going back to normal. It isn't a slow drop as it should be when you let off the gas and coast

 

Vaccum leak?

 

clean the MAF

 

If it was a vacuum leak I don't see why it would only do it when I let off just before it shifts and not any other time. As far as the MAF, it was cleaned maybe 5 months ago. Wouldn't that have an effect at all times as well?

 

That sounds somewhat normal*, how far up do your RPMs shoot up/down?

*My Tacoma is my first vehicle with an auto trans, so who knows.

 

It goes from maybe 1800 to 600 or 700 rpms in a second. If I let off the gas when it is not close to shifting it just goes down to maybe 1200 and moves a lot slower

 

I know what you're talking about. My truck will occasionally act this way around town (and thus when I'm doing it while it's trying to shift under easy driving), it's acts like a manual and as if you shifted to neutral or clutched in but the concern is how quick the RPMs drop off versus the normal slow drop.

I don't know why, probably just a quirky software thing due to timing of the shift and gas being let off. I'm more just here to say "mine doe it too" and I don't have any trans issues, so I wouldn't worry.

 

Sounds like it's the trans trying to figure out what the hell you want it to do?

If you run it to a shift point and then take the demand away, it's going to correct itself. Why are you dropping throttle at shift points? I'm guessing the RPM drop is because you're making the trans be between gears, then it downshifts because there's no more throttle input. You're forcing the trans to hunt for gears because you're not driving properly.

Trying to make a fart can sound like a manual trans?

 

I don't let off the throttle at shifts points on purpose. I have to if I have to stop or turn a corner or something. I know the transmission doesn't down shift when it happens either. It almost feels as if your truck died. Watching the needle is strange, it bounces down and up and down as if someone were playing with it.

I appreciate everyone's input by the way.

 

Mine does the exact same thing.
Of course it has nothing to do with driving improperly ....
Sometimes you have to let off the throttle to keep speed down.
I was a little concerned about it for a while but since in every other situation the truck acts perfectly normal and even when the tach. drops there is no hesitation whatsoever, I stopped worrying about it.
I'm not even sure the engine RPM's actually drop or just the tach but like I said earlier, nothing to worry about IMO.

 

My wife's Sienna mini van does that. My Taco is a six speed so I guess I'm no help there.

Sounds normal to me.

 

Mine does it too, it's really noticeable with a louder exhaust.

 

Mine does the same thing.

 

Take neg cable off the battery for half an hour. I do this probably once a year, or every 2 yrs when the trans starts to do stupid stuff. Usually helps.
May not help u, but its free

Sounds like the trans thinking about upshifting, but when u let off, it wants to engine brake (as programmed), so the rpm goes back up?

Not sure

 

Yeah I was thinking that the transmission just sort of gets confused. If other people have noticed the same thing I probably won't worry about it too much. While I have people looking and talking, instead of starting a different thread, another thing I have noticed is the transmission almost acts like it has an extra gear when it's cooler until it gets to a certain temp. For example, it shifts into the last gear around 35mph and then does a little shift again around 38mph. Only does it when the transmission is not heated up to normal temp. Has anyone else noticed that?

 

Should actually hold gears longer if cold....

That feeling may be the convertor lockup.

Fwiw i never cruise in D, if around town and under 50, i stay in 4.

Whats being used to monitor trans temp?

 

I have an ultraguage. What is your reasoning behind not using cruise and staying in 4 in town?