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How do ABS brakes work on 91 Burbs?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Eric M., Jan 5, 2002.

  1. Eric M.

    Eric M. 1/2 ton status

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    I always thought there would be a sensor at the rear wheels, but I don't see any. How do they work? Could I put a hydro boost with my rear ABS set up on my 91 Burb? Could I swap reaf diffs. or would I need to find one with ABS?

    Thanks,

    Eric

    Blown K3500 [​IMG]
     
  2. woody9

    woody9 1/2 ton status

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    Seems I asked that very same question a while back when i did the 14 bolt conversion on mine, but danged if i can remember the answer. I think it's controlled somehow 'upstream' from the rear end (and i bought that explaination then), but now thinking about it, what keeps the rear brakes from doing that?
    Unless the pressure is reduced when the electronics sense speed and the drive train isn't moving?
    Another thing, is that 91 was a REAR ABS only! Not 4 wheel!
    Not sure this helps... but we can go from there! I'm interested in any replies as well!
     
  3. Eric M.

    Eric M. 1/2 ton status

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    Don't know why I didn't think to look in the shop manual, I just ordered it and it's sitting right in front of me! It seens the only feedback the ABS control modual receives is from the brake lights and transmission speedo connection. That is straight out of the GM service manual for 91 Burbs. They make a fuss about recalibrating the speedo if you change ratios or tire size and provide a chart which goes up to a 31" tall tire and 4.56 gears. Did you have any problems with the 14 bolt swap? Did you change ratios or tire size and recalibrate? How does the ABS work now - ever lock up the rears? I'm thinking you could swap in the Hydroboost if it fit. All the ABS does is regulate the pressure from the master. I doubt it cares where the pressure comes from.

    Eric M.

    Blown K3500 [​IMG]
     
  4. woody9

    woody9 1/2 ton status

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    no 'serious' problems with the swap. Even able to keep my dual front shocks!
    Found a pair out of an 80 pickup with 4:10s to replace my 3:42s (i was twisting splines and/or worse pulling the camper)... for $100/end. Expensive part was 8 lug rims/tires, but got a set of factory take-off ralleys in Elkhart, Ind for < $500 (i think that's what it was??)...
    Haven't done any re-cal yet, but it's running approx 20% high. Keeps me under the speed limts by far when it's near pegged (85? and hitting the trip-meter reset post) and -20% is 17 lower, so that's actually about 68......
    Course it makes figuring mileage a nightmare!
    Understand i can get an adapter for the 91 that get's certain pins clipped depending on tire size/ratio/etc to bring back to normal. Don't recall GM part nr, but about $25... Just been dreading pulling dash apart to put it in.
    Also added 4 row rad & tranny cooler @ about the same time to improve towing.
    It's SWEET now! and still reasonable mileage.
    Think the 4:10s were offset by going to 16".
     
  5. Eric M.

    Eric M. 1/2 ton status

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    What size tires you runnin'?


    Blown K3500 [​IMG]
     
  6. woody9

    woody9 1/2 ton status

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    LT 245x75x16 M&S Generals.... Nothing to write home about.. but when doing the 6 - 8 lug conversion, I was trying to keep some of the costs down.. Will probably go with some Michelins once these dogs wear out. The truck doesn't see too much off road any more or it'd be some BFG's!
    <a target="_blank" href=http://www.mwt.net/~woody9/trailer.jpg>http://www.mwt.net/~woody9/trailer.jpg</a>
     

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