ABS doesn't work in 4wd
 

I am enjoying 4 weeks of job training in Louisiana right now, but when I left Canada two weeks ago I had the pleasure of driving in my first snowstorm with my Ram. I did some experimenting on some very icy roads and was very disappointed with the abs on this truck. When I tried to stop in 4WD I did not slow down at all! It seemed like the abs on the front and rear axles were fighting each other. The front and rear axles would lock and unlock at different rates, causing torque to wind up though the drive train. When I shifted out of 4WD, the ABS felt better, and I actually started to slow down a bit, but it still took a very long time to stop. I know I could stop a lot quicker if I didn’t have abs. The first thing I am going to do when I get back to Canada, is disable the abs.

I hope I can just pull a fuse to disable the abs, or is it more complicated than that?

How does everyone else like their abs, during the winter?

Carl

I had the same thing with my truck...barely touched the brakes and got the buzz in the pedal and no feeling like they were stopping. Let off geared down but still slid. Never thought to take it out of four wheel drive, just wanted it to stop before I went through the red light.

I am not a fan of abs.

I'm old school myself.
I want total control over my braking ability.

Noticed this last winter as well.
4 wheel engaged, I was sliding into the intersection.
Shifted to 2HI and the pedal started pumping itself hard enough to knock my foot off it.

Next intersection I left it in 4wheel and did the pumping myself and was able to stop just fine.


phox

phox - so what are you saying... just pump a few and every works out.. "WITHOUT" really looking or thinking about it.. what is the thing with ABS anyway... how should it work and how is it not working????

This is my first ABS equipped vehicle, it may very well be working as it should.

It did startle me when it started pumping itself, which could have made me release the brake, or not push as hard as I should have been.

I remember reading or hearing something about it being disabled while in 4x4,
or reduced in 4X, or something like that.

I did approach the next intersection a bit slower than the first. :rolleyes:

phox

If the roads were truly ICY, then ABS isn't going to help much. Neither is pumping, gearing down or whatever. You have to have SOMETHING for the tires to grab on to in order to slow down.

ABS brakes don't allow the tire to stop spinning (lock up) what it does do is cycle pressure at thousands of times per second to slow vehicle and maintain control of vehicle as long as tires are getting traction on road surface. The feeling of the pedal "pushing back" is normal just continue applying pressure to pedal.:D

When you are in 4x4 on these trucks with the transfer case it has, the front and rear driveshafts turn the same speed. This is causing what you are describing. When in 2wd the ABS can control the wheel speeds a lot better. The 4wd can cause the wheels to all slip more and fool the sensors into thinking all the wheels have good traction and are slowing like a normal stop. On a lot of 4x4 vehicles, ABS is not wanted in 4x4 mode because it can cause all wheels to lock up. Range Rover disables it in 4wd low but their system allows differentation between the front and rear driveshafts unless in locked mode.

You also have to "push harder" on the pedal when it starts modulating to make the truck stop quicker...It changes the input. Go find a slippery spot and try. It makes a difference.

I think the ABS won't activate below 20ish mph so you have to get the speed up to test it....:D I've tested mine and I feel I could do a better job till I found out how slick it really was! Stand on the brakes and you can still steer an important feature!

too early for snow here... but this has me curious.
first, I am a big ABS fan. In my Caravan I was cut off going 60. I had almost nowhere to go but I was able to stand on the brakes AND steer around the car in front of me. Steering and braking hard is a big benefit. Eliminating rear wheel lockup and the possibility of spinning out is a big benefit.

I guess I need to wait for some ice and experiment a bit.