Spagolli94

I have a dumb newb question...

When I'm driving on the highway in 6th gear (auto mode) and I give it just a little gas, the car feels like it does a half downshift. The revs jump maybe 500 RPM or so, but doesn't actually drop to 5th. If I give it a little more gas, it might go ahead and downshift to 5th.

But when I'm in manual mode and give it a little gas, it never does these little half shifts.

Why is this?

drbazing

I'm not entirely sure, but from my experience of driving a manual car, it might have something to do with how the clutch works in automatics.

JCWong

I've noticed that too, I then tried to shift down to 5th and rpm goes up more depending on speed. anyways my mechanic friend from Lexus once told me there are actually 8 injectors in our cars, wondering if it's some sort of gas saving feature of our cars

Spagolli94

I don't think it's related to gas or the engine. It's definitely the transmission.

Is it something to do with the torque converter? Just found this description of what torque converters do:

"The torque converter is designed to take the place of a clutch assembly that a manual transmission uses. It also multiplies engine torque so you can take off from a dead stop easier. In addition to that, it also houses what is referred to as the TCC, or torque converter clutch. This is a clutch and works in the same way a manual transmission's clutch works. It's there to prevent slippage that normally occurs within the unit. At cruising speeds, the clutch locks up and allows full engine torque to be transferred to the transmission.

It's difficult to check, but as your vehicle is shifting through the gears, count the shifts. If you have a four-speed transmission, count up through the gears as it shifts. After the transmission shifts into fourth, you might feel another shift after that. This is likely your torque converter locking up. When it's working properly it might feel like another shift at cruising speed."

So then my question becomes... Why does the torque converter "unlock" to give this sensation of a half downshift when accelerating in auto mode, but stays "locked" in manual mode?

Loe

It's possible that acceleration would be improved in that current gear with simply having the TC unlocked. Although there isn't a direct connection, the fluids being moved around when it's unlocked may provide an opportunity for the TC to multiply TQ.

....I could be wrong though, I'm not an expert with automatics (It's actually my first since I was 18 lol)

Spagolli94

I've felt this sensation in many automatics I've driven before. Often, you'll notice it the other way around - once you reach cruising speed on the highway, you'll notice the torque converter engaging because it feels like a slight upshift after you're already in the highest gear. I'm not surprised that I feel it as a slight downshift as well. But I am surprised that I don't feel it when in manual mode. It's almost like when you're in manual mode, the torque converter stays locked.

DoomBuggy

iTrader: (1)

Ive noticed this too; glad im not the only one. It can be frustrating to me when riding in 6th and I just want to quickly punch it past someone. Instead, it revs into this other half gear and can affect the smooth takeoff (sometimes even bogging it down). Its an equally embarrassing sound too, with exhaust.

I have began to drive more and more in Sport, sometimes with TRAC OFF (long press) as well. You definitely dont feel the restrictions and half gears when driving like this. Makes me wonder why the car is even tuned that way, when theres seemingly a whole other way of shifting with a few options on/off. One thing i will say is that driving in these different modes consistently makes the car adapt/learn how you prefer it to drive and shift. Once I switch back into Normal with TRAC on, the car will maintain my style of driving from the previous mode.

Can anyone confirm whether driving long distance or at higher speeds with TRAC OFF would have a negative effect on the transmission or engine?

GrandSedanFan

iTrader: (1)

It's not a half gear. It's the torque converter unlocking so that it can actually multiply torque. This is actually not that bad on the 14 IS350 AWD Luxury that we have. Granted, I don't notice it that much. That may have something to do with the fact that I drive it in Sport 99% of the time. If I recall correctly, the transmission computer is programmed to keep the TC locked most of the time to give you better control and throttle response, akin to driving something with a true direct connection, like a manual or a DCT.


The TC horribly intrusive on my 10 RX350. So much so that I gave up on buying out the lease and just let it go back. I suspect an RX350 F-Sport would have been much less annoying for my personal sensitivities.