Not really GX specific, but in case anyone wants a good detailed explanation of the full time 4WD system vs. part time 4WD in Toyota/Lexus, this video explains it.
Which 4WD System Is Best?
- Thread starter JPE
- Start date
Note that all new 2024 Lexus GX 550s have full-time four wheel drive with a limited-slip center differential and an electronic locking center differential. The limited-slip center diff allows you to drive on-road in four wheel drive without binding the drivetrain and the power sent to front and rear wheels can vary depending on traction needs. The locking center diff feature allows you to lock the center diff to send exactly 50% power to the front & rear axles for maximum off-road traction when needed.
The Overtrail variants also have a locking rear differential which prevents one of the wheels on the axle from spinning if it has less traction.
Think of how the engine's power is transmitted to the wheels.....even with full-time four wheel drive, an open center differential allows all the engine's power to go to the front or rear axle. If the front wheels are on wet ice and the rear wheels are on rock, then all the engine's power would go to the point of least resistance and just spin the front wheels. A limited-slip center diff helps avoid this problem but a locking center diff solves this problem by making sure 50% of the power is going to the rear axle. So the front wheels can spin on the wet ice but the rear axle will have traction and move the truck forward. However, if one of the rear wheels is also on ice, then that 50% of rear axle power will all got to the rear wheel on the ice. This is where the rear locker comes to the rescue by locking the 2 rear wheels together so that half the rear axle power goes to that 1 wheel with traction. The most frequent use of the rear locker is when you are cross-axled and one rear wheel is up in the air, or is nearly up in the air with very little weight on it, and thus very little traction.
The Overtrail variants also have a locking rear differential which prevents one of the wheels on the axle from spinning if it has less traction.
Think of how the engine's power is transmitted to the wheels.....even with full-time four wheel drive, an open center differential allows all the engine's power to go to the front or rear axle. If the front wheels are on wet ice and the rear wheels are on rock, then all the engine's power would go to the point of least resistance and just spin the front wheels. A limited-slip center diff helps avoid this problem but a locking center diff solves this problem by making sure 50% of the power is going to the rear axle. So the front wheels can spin on the wet ice but the rear axle will have traction and move the truck forward. However, if one of the rear wheels is also on ice, then that 50% of rear axle power will all got to the rear wheel on the ice. This is where the rear locker comes to the rescue by locking the 2 rear wheels together so that half the rear axle power goes to that 1 wheel with traction. The most frequent use of the rear locker is when you are cross-axled and one rear wheel is up in the air, or is nearly up in the air with very little weight on it, and thus very little traction.
- Thread starter
- #3
A point made in the video at the 10:35 timestamp is that the locked center diff only splits torque 50/50 if both the front and rear have grip. When locked it will send up to 100% (although maybe not in the Toyota/Lexus design) to the end (front or rear) that has grip if the other end is slipping).
Interesting, I will have to look into that...
- Thread starter
- #5
It surprised me too. I'm going to have to see if I can find any other information on the subject, but that YT channel is usually solid on technical details.
Not quite all the 4wd/differential offerings of the bronco badlands I have but the gx550 is miles ahead in quietness, steering, driving experience.
Is the Bronco solid front & rear axles? Which reminds me...referring to front axle is a habit from my old Land Rover days. The GX is obviously the double wishbone independent front.
Bronco has IFS in front which drives better on the road which is what I use it for lol
