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1994 GMC Sierra 1500 2wd LTE
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I have no clue whats causing it, but the rear of my truck bounces when im braking from 45 or over. The peddle also pulsates when this happens. Any ideas?
 

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Welcome to the Forum. Let’s start with your truck info. Pedal pulsing is usually indicative of an operating anti-lock braking mechanism.
 
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Depending on what it has for a brake system, it could be badly warped rotors or drums in the rear too.

If it uses rear brake drums try using your parking brake a little to see if it still does it at those speeds.
 
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Discussion Starter #5
Welcome to the Forum. Let’s start with your truck info. Pedal pulsing is usually indicative of an operating anti-lock braking mechanism.
1994 gmc sierra 1500 2wd. That brings up another point. my abs light has been on since the day i bought it. Never figured out whats caused it.... Well... Untill I made this thread atleast.
 

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I'm thinking it might be the same reason that you sometimes see the rear wheels of a trailer (tractor trailer combo) bounce when brakes are applied, anyone know why that happens? Is it too much brake and an empty trailer?
Could that be what is happening here?
 
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Hey, Ray, you got me curious. Here’s one possible explanation for a tractor trailer to hop.

As to the ‘94 C1500, it could be the antilock is broken and the rear brakes are set a little too close. The rears lock up on you instead of cycling the valve to keep it out of a skid scenario.
 
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Hey Greg, I hear ya with the ABS; but he was saying when braking at 45 mph, wouldn't ABS be disabled at 45?
 
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If you don't know how to do it, and I'm guessing you don't, and if you really need to keep the spending to a minimum, maybe get on craigslist and look for a mobile mechanic or self-employed mechanic for hire. It is obvious you have a serious problem with the rear brakes. It might be that one of the brake shoes is completely worn out and to the point of mechanical failure. It might be that one or both drums is warped badly, say from a dragging shoe causing overheating. It might be that one or both drums have grooves worn in them from completely worn out shoes letting the rivets rub the drums. The pulsating pedal is likely caused by the anti-lock system activating when a tire bounces off the ground allowing a wheel to lock, or some weird pressure backfeed from whatever rear brake oscillation you have.
 

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I have no clue whats causing it, but the rear of my truck bounces when im braking from 45 or over. The peddle also pulsates when this happens. Any ideas?
Since you have a ABS light, one or both of the wheel sensors are bad. When applying the brakes, the ABS doesn't see any pulses from the sensor so it is assumed it is locked up, thus the ABS engages. It sits somewhere near the rear wheel bearings and they are threaded into the axle housing. It uses the bearing or the axle splines as a reluctor. It is a relatively inexpensive part and an easy job to do. Before going nuts into other fixes, replace both of them. At the auto parts store. have them scan for codes. It will show which wheel is the problem.


 
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