was just wondering how you tell when the RABS is working, noticed the other day when i hit the brakes hard the speedo would drop to zero and when i let off it jumped back up, then i realized it was because i was sliding. thats when i thought the rear wheels shouldn't lock up becuase i have RABS, i dont hear anything buzzing like new abs systems dont feel anything in the pedal and the light isnt on, but it doesnt come on and go off like it should when i start it. so the question is, how do you know if RABS is working? thanks guys

 

I don't think the back does enough braking for them to lock up under normal braking. I don't feel them slip in the back unless I push the pedal to the floor on ice and then I can feel a little pulsing in the peddle and the whole truck slides to the side some. My ABS light comes on for a few seconds and goes off when key is first turned on.

 

After I replaced the RABS hydraulic unit on my old 1992 F350 I could hear the valve activate on slippery surfaces. Prior to that there was no noise and the rear wheels locked up very easily. If the RABS light does not come on when you cycle the key then the bulb could be bad/removed or the RABS controller may be removed/disconnected.

 

the light comes on and off like it is supposed to, i guess one thing i am assuming is that the speedo reads its speed from the back tires? if it reads from the front (which i dont think it does could be wrong) than it could be the RABS is working fine but the fronts lock up

 

Speedo/RABS reads off the rear axle.

 

The way to find out if your RABS is working is to jump on the brakes as hard as you can like a panic stop from about 60MPH. If you hear thumping under the truck and the brake pedal falls out from under your foot such that you soil yourself - it's working as intended.

 

LOL, i remember the first time the pedal dropped like a rock on me, i thought i was going to kick a hole in the floor board.

 

i'll have to try that, do you need to go that fast or can you just hammer on the brakes, the roads here suck so bad even 50 mph is a dream

 

This test will work at lower speeds, but the reaction won't be as violent so you may miss the opportunity to soil your drawers!!

I know mine has kicked in as low as 30MPH when a genius in a Civic couldn't wait for me to get by before he pulled out from a side street.

 

i tired it on an icy street at 35 mph and nothing, just started skidding, then it started skidding sideways

 

Back when I had my '95 F-150 it was really obvious that the RABS was working when stopping on icy roads. The front end would go wherever it wanted and the rear end always went straight toward the front end. Without RABS the back end will usually start going sideways when stopping on ice.

The RABS was even more obvious if I got the truck sideways before I hit the brakes. Then the front end would slide back in front of the rear and I wouldn't be sideways anymore.

Regardless of that though, if you're speedo is reading 0 then your rear ring gear isn't turning. If you are in 4wd it could be that your front brakes are locking your rear tires therough the t.case, but if you're in 2wd then the RABS can't be working.

 

yep must not work than, i only have 2wd, 4wd is just a dream at the moment