REAR BRAKES/TRANSMISSION

chimon1

I have my 2005 Sequoia since 2012 and I see that most of us have Trans. Problems. Recently I was talking to my
friend about the size of the Rear Brake Rotors. It is understandable that front breaks work first, Per Toyota, and because of the distance for brake fluid to travel further the rear brakes take action later. So Toyota decided to put small
rear rotor and small Brake Pads (thus rear pads are changed twice for one front pads). Anyway I am just curious as to
the thought that this silly design flow may the the cause of our Trannies failing prematurely. As discussed by many Experts and non experts the Drive Shaft or the tranny might be at fault but I think because of the Rear Brake acting later then front brake this puts a Helluva strain on the Drive shaft and the tranny as the vehicle comes to a stop and from high speed the vehicle tilts forward very awkwardly and the tranny does not have time to quickly fall back to
Neutral or First gear fast enough and the delay is what you hear as a THUD or being REAR ENDED

kyfdx

@chimon1

Brake circuits are a closed hydraulic system. Also, circuits are dual, diagonal. (front right, left rear). The application of brakes is not dependent on the length of the line from the reservoir or pump. Both front and rear operate simultaneously.

With the extra weight in the front of the vehicle, and the weight shifting forward during braking is why the front brakes take on the majority of the braking duty, and why the rotors are bigger in the front. (and, why the front pads may wear more quickly).

Most front engine/RWD vehicles operate this way.

chimon1

Agreed but Isee some tiny cars with much bigger rear Rotors the Sequoia Rear Rotors.
That is what prompted me to comment about rear Rotors.

thecardoc3

chimon1 said:

Agreed but Isee some tiny cars with much bigger rear Rotors the Sequoia Rear Rotors.
That is what prompted me to comment about rear Rotors.

There is a lot more to this than most realize. In many cases you will see the front rotors are vented to help dissipate the heat that is generated by stopping the vehicle while the rear are not. Since the rear do less of the braking, they don't generate the same amount of heat so cooling isn't as big of a concern. Some cars don't use vented rotors on either axle. Now other components have the responsibility of getting rid of the heat that is generated by braking.

There is no connection between the transmission life and the brakes as originally theorized above. Transmission lifespan is more dependent on driving habits and maintenance.

thecardoc3

kyfdx said:

@chimon1

Brake circuits are a closed hydraulic system. Also, circuits are dual, diagonal. (front right, left rear). The application of brakes is not dependent on the length of the line from the reservoir or pump. Both front and rear operate simultaneously.

Yes and No. In practice the rear apply just slightly before the front and if you have a vehicle with dynamic rear proportioning (done by the ABS controller) the rear will also be more aggressive than a conventional system. They still will only do about 20-30% of the braking or else lock up could occur and ideally the engineers want to avoid that.

About being a closed system., that's true until it isn't. Under most "normal" stops it would be correct. However, the moment the system has to activate the dynamic proportioning, or the ABS system needs to become active the first thing the ABS controller does is isolate the wheel that is locking up and it then controls it as an individual system.