vibration when I step on my brakes...!

[Aquiles]

Hello everyone, I need some help/advice... I have a 1996 1/2 ton, C1500 short bed, I am having an issue that when I am going over 40 mph and I step on the brakes the truck vibrates like crazy, I attacked the obvious and changed the rotors and new brake pads but the problem persisted, I checked the ball joints, bushing all the tie rods, pitman arm and anything else I could think would cause it and couldn't find the culprit , this weekend I replaced the the upper and lower control arms with JDM tubular with a 3" drop, I also installed original height moog springs since I had cut the original ones, I also went ahead and replaced all of the steering linkage with all moog parts, I have yet to drive the truck because I did not replace my shocks and am waiting for them on order as well as urethane sway bar bushings since those were shot too, I have read a few threads and talked to a few people that were never able to fix the issue no matter what they did, I should be able to get it back on the road by the weekend and get it aligned with hopes that this solves my problem, any thoughts?

[95 S_Trucker]

Did you check out the drums in the back?

I have also had new rotors not be true out of the box.

Do you feel the vibration more in the seat? or side to side in the steering wheel?

An easy way to check for a rear pulsation(for drum brakes) is to slowly apply the parking brake while driving. If it pulsates/shakes the same, you will know its the rear.

[iluvmy72]

How did you check that stuff.....many times the whole thing has to be lifted to find the problem.....misaligned under carriage sounds like it to me but I think you need to take it in....I know you want to do it yourself but this is something I would not want to drive going down a mountain or hill. I would definitely take it in to a shop.

[Aquiles]

air in the brake lines???

[Boog]

No. Air in the lines will cause a soft pedal but not a braking vibration. Usually a quick pulsing at the brake pedal is due to warped front rotors, sometimes rear drums. Under hard braking and bumpy road the anti-lock brakes can activate causing a buzzing you feel through the brake pedal.
An out of round wheel or tire can cause pulsing.

For years I thought brand new drums and rotors were ready to install and go. A few people told me they have all new rotors and drums turned to ensure they were true. I thought it was ridiculous. Brand new parts are supposed to be ready to be used aren't they? It was explained to me that new drums are "dumped" in a big box or crate for shipment and tend to warp during the ride across the pond. May be but I don't think so. You can expect used parts to be out of round but new ones? come on!

[Aquiles]

Now that I stop and think about it I really feel the vibration in the pedal...

[95 S_Trucker]

Originally Posted by Boog

No. Air in the lines will cause a soft pedal but not a braking vibration. Usually a quick pulsing at the brake pedal is due to warped front rotors, sometimes rear drums. Under hard braking and bumpy road the anti-lock brakes can activate causing a buzzing you feel through the brake pedal.
An out of round wheel or tire can cause pulsing.

For years I thought brand new drums and rotors were ready to install and go. A few people told me they have all new rotors and drums turned to ensure they were true. I thought it was ridiculous. Brand new parts are supposed to be ready to be used aren't they? It was explained to me that new drums are "dumped" in a big box or crate for shipment and tend to warp during the ride across the pond. May be but I don't think so. You can expect used parts to be out of round but new ones? come on!

They are supposed to be true out of the box, but cheap parts made with cheap steal and a long boat ride aren't always perfect. The lathe doesn't lie.

I've gotten tired of returning brand new drums/rotors, and getting another new set that is just as bad. Its quicker for me to put them on the lathe, and then put them on the car. There are several places in this area where the parts go on the lathe before they go on the car. I don't put them on the lathe unless they cause a problem. Most of the problems I encounter are with compact and sub compact car brake drums.

[speedygonzales]

I've never encountered a set of drums that were bad. Doesn't mean they aren't out there.

To isolate back from front try stopping with the E brake.

2 things I have found since I started driving in 1977. One is, automatics have a problem with warping front rotors much more than manual tranny cars. I've come to the conclusion it's because the brakes stay tight against the rotors at stop lights and cause uneven cooling. Compared to a manual that usually takes the foot off the brakes at the light. Unless on hilly areas of course. I find it's usually an installer that causes warping though.

The other thing is uneven torquing of the lug nuts. My first encounter with this was at a tire shop. After they shot the lug nuts on with an impact, I had to replace the rotors. Never had a problem in 3 years prior.

I recommend torquing in 2 steps. I use 60Lb and 120 Lb torque sticks.

Warped rotors will show up usually by pulsing the pedal as you stop. I think many auto parts stores will cut rotors. Many don't do drums though.

[shifty]

Glad to finally find someone else that posted about this on here! Resurrecting this zombie.

I'm having the exact same issue! Sadly, looks like the OP hasn't been seen on the forum for 18months or more.

Gist: Get above 30-40 mph. Press brakes lightly at that speed, no vibration. Press brakes firmly, the harder you press, the more it feels like you're rolling over those little rumble strips they put before stop signs (see below) until you get under 20-25mph. Brake as hard as you want under 25 and you're golden.

Front rotors look great, lots of life, same as front pads. Haven't checked out rear drums. Wasn't sure if this is something ABS sensors could cause?

Literally no other braking issues (other than typical spongey pedal) and this only shows when braking aggressively while at a higher speed.

[Palf70Step]

To me that sounds like the antilock breaks pulsing. MY old 92 was the one I felt it the most from during harder braking.

[shifty]

Originally Posted by Palf70Step

To me that sounds like the antilock breaks pulsing. MY old 92 was the one I felt it the most from during harder braking.

This was my thought too, Bill.

I keep hearing stories about bad wheel sensors causing weird reactions at the wheels. But I hadn't seen anyone comment yet about pulsing/vibrating as one of them.

Next time I go on a longer ride I'm going to pull the fuse for ABS and see if it still happens. If not, I guess we know what system is causing it!