Isn't it really a 6 speed transmission?

[Barak]

I recently purchased a 5th Gen and it has an extra gear between 4th and 5th:
Yesterday I took it out for a break-in drive and while driving up a slight hill in 5th gear - 70 MPH [MENTION=21408]2000[/MENTION] RPM, I very slowly depressed the gas pedal until it downshifted to the next gear down - still at 70 MPH but now @2300 RPM. I could hold it in this condition as long as I wished. Then moving the transmission in to sport mode, it downshifted to 4th gear (as indicated in the dash) and I held 70 MPH @2800 RPM.

So, my question is, doesn't this make it a 6 speed transmission and what is this elusive, un-named intermediate gear?
I know you can't shift in to this 4 1/2th gear using sport mode.
My 3rd get AT 4Runner did the same by the way.
Any insight would be appreciated.

Thanks,
Barak

 

[gbarr]

Its not a 6th gear, the torque converter just unlocked.

 

[DKFTPNYC]

I recently purchased a 5th Gen and it has an extra gear between 4th and 5th:
Yesterday I took it out for a break-in drive and while driving up a slight hill in 5th gear - 70 MPH [MENTION=21408]2000[/MENTION] RPM, I very slowly depressed the gas pedal until it downshifted to the next gear down - still at 70 MPH but now @2300 RPM. I could hold it in this condition as long as I wished. Then moving the transmission in to sport mode, it downshifted to 4th gear (as indicated in the dash) and I held 70 MPH @2800 RPM.

So, my question is, doesn't this make it a 6 speed transmission and what is this elusive, un-named intermediate gear?
I know you can't shift in to this 4 1/2th gear using sport mode.
My 3rd get AT 4Runner did the same by the way.
Any insight would be appreciated.

Thanks,
Barak

Technically, no. There are only 5 forward gears. At 70mph on a level road surface, the transmission has locked up the torque converter (not 100% sure that's the correct phrase). What you are experiencing when you hit the gas and it "downshifts" is the torque converter engaging in the 5th gear. If anything, you can think of your transmission being at 5.5 gear at 70mph. Hope this helps.

 

[(none)]

Sorry to be the ball buster:

-first, it's not sport mode

-2nd, as noted above, that's the torque converter locking and unlocking. Also, whenever that torque converter is unlocked, it's creating heat. Lots of it. Just be aware.

 

[wfo9]

Its not a 6th gear, the torque converter just unlocked.

^^ This. Every auto has this feature. You lose a lot of efficiency when the converter unlocks. That lost energy is converted to heat and will eventually overheat the transmission if you run in that condition for extended periods (the entire transmission runs on one source of fluid)

If you are towing or driving in the mountains.. It's highly recommended that you just manually shift it down, get the rpms up, and let the converter lock up.

It's not specific to 5th gear... Someone posted a chart once outlining all the conditions it will unlock in, but generally speaking... keeping the RPMs up will keep it locked. It obviously unlocks when you come to a stop.... but very little heat is generated at that point....

I've seen people go offroad and stay in 4High and overheat the trans in the process due to the converter being unlocked the entire time. This is very common in sand. 4Lo solves this problem.

In simplistic terms.. unlocking the converter is like slipping the clutch on a manual trans, but it is a fluid coupling device and pump in an auto vs friction plates.

 

[Barak]

Its not a 6th gear, the torque converter just unlocked.

Interesting, I just watched some videos about torque converters.
So, does driving in this state "between" 4th and 5th while the torque converter is unlocked and RPM somewhere between 4th and 5th values for given speed, is there loss of efficiency? Is it bad to drive in this condition for long periods of time?
Thanks - happy to still be learning something new!
Barak

 

[Barak]

Sorry to be the ball buster:

-first, it's not sport mode

-2nd, as noted above, that's the torque converter locking and unlocking. Also, whenever that torque converter is unlocked, it's creating heat. Lots of it. Just be aware.

Thanks,
I was formulating my previous response while you were answering my question.
Appreciate it.
"Sport" mode is what it was called in my Tacoma, I believe. (I know it doesn't change anything but your control over limiting the transmission to the highest gear selected)

 

[Barak]

Great information - thank you!

^^ This. Every auto has this feature. You lose a lot of efficiency when the converter unlocks. That lost energy is converted to heat and will eventually overheat the transmission if you run in that condition for extended periods (the entire transmission runs on one source of fluid)

If you are towing or driving in the mountains.. It's highly recommended that you just manually shift it down, get the rpms up, and let the converter lock up.

It's not specific to 5th gear... Someone posted a chart once outlining all the conditions it will unlock in, but generally speaking... keeping the RPMs up will keep it locked. It obviously unlocks when you come to a stop.... but very little heat is generated at that point....

I've seen people go offroad and stay in 4High and overheat the trans in the process due to the converter being unlocked the entire time. This is very common in sand. 4Lo solves this problem.

 

[03_4x4Runner]

Lock up torque converters were not made until around 1980. Every automatic transmission before this did not have a lock up converter. The old GM turbo 400, Ford C6 and Chrysler 727 trans would last forever. I used to run high stall converters on my old muscle cars and with a good trans cooler they were fine.