Rear ABS behavior

I got the rear drum brakes all rebuilt on the '96 F250. This is the only truck I've ever had with rear only abs. How is it supposed to feel at lock up? Does the pedal pulse like modern abs? Is there any feedback that you're in Abs?

Right now I have the drums adjusted a little tighter than they should be I think. I'm getting a little odor and excess heat off the back but the fronts are still locking up first under panic stops. I can't tell if the rear abs is functioning as designed or if something else is going on.

EDIT: Damn autocorrect. Can one of you mods change my topic from "AND to "ABS"?

The 91 F350 I had never had any pedal pulse when braking hard. Rear wheels would partially lock up and unlock, so the abs did work, just not as good as newer trucks. The rear brakes may need a bit of break in, then they should work better.

Thread title fixed.

Get on a dirt road with some speed and room and mash the brake as hard as you can - that should be enough to lock them up and see what abs does. (Assuming it is working :) )

I've never noticed anything different in a RABS vehicle.

Edit: different from a non abs vehicle. RABS has no pump.

I never noticed my 92 rear brakes to do much of anything and it's been in the family since new. When the parking brake freezes up, you can tell when a back wheel is locking. Otherwise I can stand on that pedal and can't get a squeak out of the rears. Like you I have tried, to see how the abs responds, but I can never get them to feel like they are locking.

On my dad's old '89 F250, you couldn't feel the RABS activate. IIRC, the rear brakes were self adjusting; they would adjust themselves whenever you were reversing and came to a complete stop.

The only issue we had with the rear brakes on the truck were defective axle seals. The seals would leak and contaminate the brake shoes. It made driving it exciting when one or both the brakes would lock up if you even breathed on the brake pedal. The Ford dealership helpfully installed defective seals 4 separate times until they admitted the seals were defective; each time requiring new brake shoes

Be aware that the fronts will still lock if you ask for more braking than the surface will support.

When rear wheel ABS activates, you might feel the brake pedal drop slightly once or twice mid-stop.

worst thing ever in the winter. ABS on dual rear wheels, fronts lock up so no steering. Drove Ford E series conversion bus for five years. Some time there would be pedal vibration when it was slippery enough for the dual rears would lock up. Not often as you had to drive by what the fronts were doing.

Thanks for the feedback. Sounds like they're basically working as designed...for what that's worth...

To ultraclyde and iceracer, RABS is designed to keep the rear of the vehicle behind the front of the vehicle, nothing more.

My '96 F-150 has slightly overactive RABS. The main thing I notice is that the overall braking effectiveness goes away when the RABS comes on, because the lack of a pump drops line pressure. So, if the RABS comes on, you've gotta hammer the pedal pretty hard, or let off and start again.

In reply to snailmont5oh:

RABS drops line pressure to rear brakes only, when it sees wheel deceleration that exceeds some threshold. Then it waits and watches the rear wheel speed. If it recovers to within a certain % of reference, the system will allow a couple of pressure increase pulses. If your fronts could be doing more work, that's not RABS's concern. So yeah, if you want more deceleration you gotta add more pedal force. RABS is physics-limited, like so many other things in life. If you do mash the brake pedal and get more deceleration, you'll also get more weight transfer from rear to front, and RABS might have to make another rear pressure reduction to manage the increased slip.