So, I have a 2021 Toyota RAV4 which was bought new and when shopping for this particular vehicle I wanted to make sure I wasn’t getting one with CVT.
I hate CVT so much. I’ve had nothing but problems with them. When I bought a Nissan Sentra years ago, the CVT transmission died at around 90k miles and cost me $7000 for a new one.
When looking at Toyotas website and browsing through their levels of rav4s I couldn’t find one with a traditional transmission. Only ECT and hybrid were available.
I also hate hybrid vehicles. For me, they lack character. This is one of the reasons why I chose the Lexus IS over the Subaru WRX AWD.
Here is the issue: I don’t know what ECT actually is. I told the dealer I did not want an electrical vehicle nor a hybrid, neither CVT — I simply wanted a traditional automatic transmission.
The dealer said the ECT was the closest thing to what I wanted, so I went with that.
But for clarification: is ECT actually a traditional transmission ? Can you explain what ECT is in simple terms so I novice may understand ? How does ECT compare to the old fashion transmission I so love ?
Your Rav4 uses a ‘normal’ 8 speed transmission, electronically controlled, as I bet all are these days. That means a computer controls the shifting, based on throttle inputs and engine speed, along with other factors.
No WRX has come with a hybrid drivetrain, but it does have a CVT (or a manual).
I test drove the WRX and it felt like a boat sailing along the sea. I couldn’t feel any shifting and the engine ( though I’m deaf ) sounds like a microwave.
The car just didn’t have any character at all.
Back to topic: You said the rav4 has a normal 8 speed transmission that is electrically controlled, meaning a computer decides shifting
Before ECT, what decides shifting in an automatic vehicle ? I’m asking to make sure if I’m understanding the difference.
Basically all modern automatic transmissions are electronically controlled transmissions/transaxles… The main difference is a not ECT trans uses mechanical controls, meaning hydraulic governors, spool valves, TV cable inputs and or vacuum modulators, where as an ECT trans will use electronic inputs from multiple engine and trans sensors that the TCM (trans computer module) and the ECM monitor and send signals to different solenoids to control up/down shifts and torque converter lock up…
That is about as basic as I can put it, but both are very complex…
Electronic controls have basically been the norm for like - what? 25 years? And they go back way farther than that. Chances are, @Clueless33 that you’ve never had a transmission that didn’t work by electronic controls. So you’ve probably always had a computer deciding on the shifting.
Manufacturers began using electronic engine controls (ECM) and electronic transmission controls (TCM) sometime in the late '70s-early '80s, so as Dave stated, you’ve never owned a car w/o an electronically-controlled transmission.
Overall, I believe that you are over-thinking the transmission issue. With the exception of Nissans, CVTs have proven to be essentially just as robust as “conventional” automatic transmissions. EVERY automatic transmission needs to be serviced periodically, with the correct fluid & filter, even if the mfr claims that it uses “lifetime” fluid. I prefer to do this at 30k-40k miles, but you’re probably okay doing it by 60k miles.
That’s what I heard — that they’re robust now. I just couldn’t find happiness with the Nissan vehicles I had. And the worst part is that I never missed a single recommended service on any of my vehicles.
I had the transmission serviced and the car began acting up later on and they rebuilt the transmission. Then the issue came back, so I purchased a new transmission ( stupid me, yes I know ) — then a new issue arose with the front axles, so I said enough is enough, and got rid of it.
With the Altima, the engine was always smoking or having the smell of smoke, so I got rid of it too, especially that Nissan would not take responsibility of selling me a lemon.
@davesmopar has had a thread going here about repairing one of his vehicle’s ECT. So he knows firsthand of which he speaks. An auto-trans has internal tubes filled w/hydraulic fluid pumped to very high pressures. To effect a gear shift a valve in one of those tubes opens and allows the hydraulic pressure to cause an actuator to move. In an electronically controlled transmission the valve is a simple electro-magnet that moves from closed to open by a magnetic force generated by electrons moving along a coil of wire, termed a solenoid. As I recall @davesmopar wasn’t sure if his trans problem was caused by an internal solenoid or another external part. He was hoping it was the latter, b/c the internal solenoids are very time consuming to access.
By contrast my older Ford truck’s auto transmission, the internal valves are small pistons that move in bores the same diameter as the piston, and a spring holds them in one position unless hydraulic fluid overcomes the force of the spring. There’s dozens of internal tubes that form a sort of hydraulic computer called the “valve body” , and the routing of these internal tubes and the valves is what makes the shifting decisions. For example
DMP may well know the purpose for each of those valve body pathways.
Before ECT transmissions shifted based on controls that compared vehicle speed (using a flyweight governor) to engine load (as measured using engine vacuum applied to a vacuum diaphragm).
Lower vacuum indicates higher engine load because the throttle is open more. At idle engine vacuum is very high because the throttle is closed and the engine is obviously doing very little work.
A governor spins at driveshaft speed and opens / closes valves based on the speed it’s rotating versus the springs that restrain the flyweights.
The comparison of vacuum modulator input versus governor input is done in the transmission’s valve body.
Lots of transmissions did not use a vacuum modulator, they used a TV cable that was a mechanical link between the throttle lever and the transmission that moved a spool valve to adjust line pressure up/down depending on the throttle given by the driver…
And some used both a vacuum modulator as well as a TV cable…
The main input to the shifting algorithm is the vehicle speed. It would still work pretty good if the shift transitions just occurred at the same speed transitions. Most driver’s prefer the shift transitions change slightly during rapid acceleration, that modulation of shift-speed transitions is what @JayWB and @davesmopar are referring to above. The part that does that is called (not surprisingly) the vacuum modulator( in before ECT transmissions).
As far as how the transmission determines the speed and uses it to effect the shifts, one way is the final drive rpm is directly proportional to the vehicle speed, b/c that’s what powers the wheels. A hydraulic pump can be powered by the same final drive, which yields a tube with a fluid pressure directly proportional to vehicle speed. That fluid pressure can then be used to open and close the transmission’s internal valves which control the shifts. For this all to work the fluid pressure must not leak down b/c of incontinent seals. When an automatic trans begins to fail, it is often b/c the hydraulic pressure is leaking down and is lower than required for proper shifting b/c of seal leaks. The seals over time change from being soft and pliable to stiff. The trans fluid contains additives to help prevent this. The reason that sometimes simply replacing the trans fluid helps is b/c fresh fluid contains fresh seal conditioning chemicals.
