THIS MAYBE A STUPID QUESTION....So I am driving with th Cruise on and going up a hill with the AC on. I feel the runner about to downshift to third but before it does it feels like in slips into 3.5 gear? It is definatly not 3rd. The rpms go up and it is for a quick second then down to third. Everytime..What is that???
"Pre"-downshift???
- Thread starter wsudu
- Start date
Register to hide this ad
Northof49
New member
That's exactly what it is....this is particularily noticable in 3rd gens such as the one in question, it really feels like that 4 speed auto is a 5 speed auto quite often!Kmvreter said:
Basically, the converter is automatically locked up during low load cruising situations for optimal fuel economy, but as load increases (ie uphill with AC on) the TC unlocks first, and eventually shifts down to 3rd if the load increases further.
I found 3rd gens to be more responsive/require less throttle angle to climb hills at highway speeds by turning off the OD. Also hunts through the gears less with OD/off.
Hank
New member
Correct me if I'm wrong, but I think it's the adjustment of the valve timing that kicks in to make the engine put out more power. In our case, it's the VVT-i. I notice the same occurence in my other vehicle (Nissan). The tachometer usually kicks up another 500 RPMs or so when it does. Another thing I noticed on the V6 w/4spd tranny is that when climbing a steep grade and manually downshifting to 3rd gear, the VVT-i doesn't kick in. The pulling power is there, but it doesn't have that extra oomph! Only after manually downshifting to 3rd and then back to 4th shortly afterwards, the VVT-i kicks in, but will still hold the tranny in 3rd gear. Thus, more power. Just FYI.
Northof49
New member
What he is describing definetly has nothing to do with VVT-i....his truck is an 02 and does not have VVT-i.Hank said:
Although your 4R does have VVT-i, I would still wager a weeks wage that what your feeling is the auto lockup torque converter and not VVT-i.
The only Toyota's that have a noticeable VVT-i switchover are the high-rev 2ZZ-GE's in the Celica GT-S, Matrix/Corolla XR-S....when the motor hits 6,000rpm, it's a night/day difference.
Hank
New member
Okay, maybe it's not necessary the VVT-i kicking in, but I think it has something to do with the valve timing (multi-steps in valve timing?). For example, if you're cruising at 70mph and you want to pass another vehicle. You give it a bit more gas and there's a little surge of power coming on as you accelerate (not an aggressive acceleration-type pass). The 4R is still in top/overdrive gear without ever downshifting to a lower gear. The tachometer kicks up (jumps, not gradual) another 500 rpms or so, but not another 1000+ rpms as it does when the tranny actually downshift a gear. My other vehicle I was referring to is a '93 Quest and it does the same thing (it definitely doesn't have any VVT-i, V-TEC, etc). Also, doesn't the torque converter fully engaged/locked-up when the vehicle is driven at speed as opposed to being stopped at a light or driving at really slow speed. I don't know much about torque converters except I know it is meant to slip at a standstill or low speeds. I've always been curious about this phenomenon. Any mechanic or knowledgable car guru wanna explain? Thanx for your input. BTW, you guys might be right about the torque converter, but since I'm no expert, I just wanted some confirmation.
Hmmm... now that I think about it, maybe my discussion is completely unrelated to the original question. If I've got it right, I think wsudu was inquiring about how the engine revs up briefly as the tranny downshifts. If that is the case, then yes, you guys are right about the auto torque converter disengaging during the shifting of gears.
Hmmm... now that I think about it, maybe my discussion is completely unrelated to the original question. If I've got it right, I think wsudu was inquiring about how the engine revs up briefly as the tranny downshifts. If that is the case, then yes, you guys are right about the auto torque converter disengaging during the shifting of gears.
Last edited:
It's definately the torque converter unlocking. It can easily be proved by going up a long hill with a trans temp gauge installed, hehe!
The reason the increase is so minor is because the stock torque converters have a (I THINK) 1.3:1 ratio.
I think it's kind of cool, when ascending, it doesn't let the speed drop while at the same time not overworking the engine in 3rd gear!
The reason the increase is so minor is because the stock torque converters have a (I THINK) 1.3:1 ratio.
I think it's kind of cool, when ascending, it doesn't let the speed drop while at the same time not overworking the engine in 3rd gear!
Iowa4Runner
New member
If the RPM jumps up without a proportional jump in MPH, then it's definitely the torque converter unlocking. If it's a big jump in RPM, it's a downshift...
RXvedub
New member
Torque Converter You can also notice is on the previouse generation when you are on the freeway, have ECT on, and turn overdrive 'on' the RPM's will jump with more power, then shift to the next gear.
And HANK, its the TC. I can post a map of the Valve timming change if enough of you were realy interested.
AND... on a 2ZZ-GE the change at 6,000 RPM is 'lift' hence the name VVTL-i wich is a change in the lift and duration of the intake cam.
(previously owned a 7th gen Celica)
And HANK, its the TC. I can post a map of the Valve timming change if enough of you were realy interested.
AND... on a 2ZZ-GE the change at 6,000 RPM is 'lift' hence the name VVTL-i wich is a change in the lift and duration of the intake cam.
(previously owned a 7th gen Celica)