ABS "AfterPulse" Problem (1 Viewer)

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Hi all, I searched and saw threads that talked about ABS overreacting with REVOS (I happen to have revos, and I happen to love them ) but I read that to mean that the ABS activated sooner or stronger than with other tires out there.

What I have happening is different and I have sensed it for some time on regular pavement but the last two days or so we have had lots and lots of sheet ice to play on and I've really got the feel of the problem:

Driving over long smooth stretches of ice and purposely hitting hard on the brakes gets the ABS going almost as soon as you hit the pedal, which I would expect. Once ABS is activated, the vehicle will stop with good steering control but poor braking ability, which I would not expect. I tried multiple times to really recreate one "run" after another and I am 100% sure I can consistently get shorter stopping distances with the ABS off such as what occurs with CDL activated; with the ABS off I can almost lock up the tires til the vehicle starts to skid sideways and then just let off little and get it right back to that threshold. .

The last thing is the most unexpected thing and I recreated this with both front wheels braking on ice and with one front wheel braking on ice while other is on regular pavement. I have a predictable after pulse whenever either one or both of my front wheels go from ice to pavement while braking and I'm not talkin like a split second worth but a good full second to two even. It is strange sweaty fealing and its like you cannot convince the system that it is on good ground. If as soon as the tires go from ice to pavement you let off little on the pedal, just enough to disengage the ABS, you can then hit the brakes as hard as you want and the vehicle brakes as hard as ever.

I would love to learn any theories on this. None of the obvious things stand out - no problem with pad or rotor or MC or anything and, great braking ability other than in this specific mode. Thanks. :cheers:
 
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Hmm, You got me Turbo. I have something of a different nature going on with mine. I just recently serviced the front axle and when putting the ABS sensors back in didn't bang them all the way down so that one tire was engaging while the other was not causing a shuddering and hard pull towards the right. After banging the offending sensor all the way down the ABS light went off and everything seemed to be normal again.............except now when I'm slowing down and coming to a stop, when I'm almost stopped in fact the front end seems to shudder evenly as if the ABS is engaging unecessarily on both tires. Also the light will flicker on for a couple seconds when this happens and then go right back out. I know this doesn't really answer your question but it just seemed slightly similar so thought I would post it. If I solve my problem as I'm pretty sure it is sensor related I will let you know. Have you recently done any work on the front axle? brakes etc.....??
 
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reffug,

That is the same exact description I had following my axle service and just prior to getting my ABS light to stay on...and then pulled the codes and my right front sensor was toast.
 
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reffug said:
Hmm, You got me Turbo. I have something of a different nature going on with mine. I just recently serviced the front axle and when putting the ABS sensors back in didn't bang them all the way down so that one tire was engaging while the other was not causing a shuddering and hard pull towards the right. After banging the offending sensor all the way down the ABS light went off and everything seemed to be normal again.............except now when I'm slowing down and coming to a stop, when I'm almost stopped in fact the front end seems to shudder evenly as if the ABS is engaging unecessarily on both tires. Also the light will flicker on for a couple seconds when this happens and then go right back out. I know this doesn't really answer your question but it just seemed slightly similar so thought I would post it. If I solve my problem as I'm pretty sure it is sensor related I will let you know. Have you recently done any work on the front axle? brakes etc.....??

Thanks man, no, not any real recent work on the front axle, but again, this is something I sensed lightly for long time now and with the super slick ice we have had I have been able to really try to make the problem present more. Although your problem sounds somewhat different. I would not be surprised if the same things are out of whack such as ABS sensor or ABS computer. Likewise, if I solve the problem I will let you know, take care bro!!! :cheers:
 
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TX_TLC said:
reffug,

That is the same exact description I had following my axle service and just prior to getting my ABS light to stay on...and then pulled the codes and my right front sensor was toast.

TX, thats helpful thanks man, am I reading you right that the OBD codes told you the right front sensor was toast, or was it some other specific diagnostic to do??? I have no codes or lights so not sure where to go from here. Thanks again though. :cheers:
 
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turbocruiser said:
TX, thats helpful thanks man, am I reading you right that the OBD codes told you the right front sensor was toast, or was it some other specific diagnostic to do??? I have no codes or lights so not sure where to go from here. Thanks again though. :cheers:
It's been over a year but IIRC the code specified the RF sensor failure.
 
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TX_TLC said:
It's been over a year but IIRC the code specified the RF sensor failure.

Oh :censor: :censor: :censor: and double :censor: . Well when you read this as I am sure you will what do those things go for Dan? Might as well buy both if thats the problem with the mileage and what you previously told me about them only lasting about 200K.
 
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Those things are not cheap - comes with the harness all together IIRC. Couple trucks being parted now in the For Sale section.....

DougM
 
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reffug said:
Oh :censor: :censor: :censor: and double :censor: . Well when you read this as I am sure you will what do those things go for Dan? Might as well buy both if thats the problem with the mileage and what you previously told me about them only lasting about 200K.
Yes you might as well replace them both since that is the only way to buy them! ;) IIRC (again) it was like $550 for the set. :doh: I know...there is a reason I haven't got them yet.

You might check into getting some used ones. I did but finally decided (FOR ME) this wasn't a part that I wanted to pick up used. Especially since the only used ones I could find were still going for around $200. No thanks...since there is no way to tell if or when one of them would fail as well.

Sorry Jamie...guess the 80 is looking for a nice Christmas ;)
 

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