ABS question

[LXA]

OK...stupid question #1 for the day. Since we finally got enough snow to play in, I thought I'd check out the ABS. So, coming up to a stop sign, I hit the brakes pretty hard to see what would happen. I slid a little (which is what I wanted) & stopped just fine, but didn't feel the familiar ABS thump on the pedal, nor did the light come on. Is that normal or do I have a problem? I was in 4X at the time. Does that make any difference? You may now start laughing. :

[directory]

of course i don't have the work manual to back this up (at work right now), but i thought i read that abs is shut off in 4 wheel drive...***i may be wrong in this***

because of the wierd spinning ratios of the front and back....again i could be totally wrong and can't verify the manual at this time. (i could have the wrong vehicle in mind also)

[Canucklehead]

This is right out of AllData's Anti-Lock Brake Section for

Rear Wheel Anti-Lock System Description and Operation


SYSTEM DESCRIPTION
The system monitors rear axle rotation during braking. If axle speed decreases at a rate that indicates rear wheel lock-up, the system adjusts hydraulic pressure to the rear brakes.

System Design
The system is designed to minimize rear wheel lock-up under severe braking conditions or when traction is reduced due to slippery roads. Under normal operation, the vehicle braking system will function like a conventional braking system.

Lock-Up Condition
The Rear Wheel Antilock (RWAL) system works only when the brake pedal is applied and possible lock-up conditions exist. It cannot cause the brakes to be applied without the pedal being pressed.

Pedal Pulsation
Normally, the driver cannot tell when the RWAL system is operating. Occasionally, there may be a slight brake pedal pulsation when the RWAL system makes a pressure correction.

RWAL System Self-Check
The RWAL system conducts a system self-check when the ignition switch is turned on. The "Rr ABS" lamp will stay on for about two seconds after the engine starts, then goes out when the system finds no faults.

RWAL Maintenance
There is no scheduled routine maintenance for the RWAL system beyond the required normal brake system maintenance items. If any problem occurs in the normal brake system that causes the "BRAKE" indicator lamp to light, the RWAL system will disable itself and the "Rr ABS" indicator lamp will also come on.

RWAL Operation In 4WD
The RWAL system will operate while the vehicle is in 4-wheel drive (transfer case in 4L or 4H); however, if the front brakes lock in 4WD, the rear wheels will also lock, regardless of RWAL system operation, because they are mechanically connected to the front wheels through the transfer case.

[directory]

ahhh...now i remember..it was the word "however" that i was hung up on. abs will work in 4x4 mode.

[LXA]

Thanks very much for the help! It doesn't sound like there is really any way to "test" the ABS in 4X like I was trying to do. Guess I'll wait for the next snow and try it again in 2X to see if there's any difference. Or maybe just wait until the idiot light comes on...

[Canucklehead]

Originally Posted by LXA

Or maybe just wait until the idiot light comes on...

The light doesn't just come on to let you know that your ABS just accuated. It only comes on during the lamp test and when the ABS system has a problem.