I'm lost. I think I had a problem with my rear brakes. After a long trip the brakes started pulsating when coming to a stop. I figure I must have misadjusted them when I put new shoes on and they overheated and warped the drums. So I take the drums to an auto parts store and they put them on their machine and it looks as if they're warped. We weren't positive because he had alot of trouble mounting the drum on their machine. So, I go ahead and do a complete rear brake job with new drums, all new hardware, wheel cylinders and rear brake hose. Problem is it's still pulsating when I put on the brakes. I did have the mushy pedal thing but realized that was due to the drums being too loosly adjusted. I'm still not sure I have them tight enough but would rather let the adjusters take it the rest of the way. When I took the drums off it looked okay but there was a big shiney spot on the rear shoe on the passenger side. I don't know what to do next......is there something else back there that could be causing this or are the brakes the most likely cause? Maybe the RABS? I did have a leak in the rear line that I had trouble fixing when I reaplaced the hose. It made a mess but the master cylinder was never low. I have heard of cases where running the ABS module dry on other cars required a dealer visit. I also bled the brakes from furthest to closest including the ABS module.

I am having some other issues that I suppose could cause some trouble but I didn't think it would be like this. The drive shaft is eating through transmission tail shaft bushings. I replaced the first one since the truck was new less than a year ago and again the yoke is loose in the housing. I do get a vibration from that but it's frequency is much quicker that the one I'm trying to find. Also, my newly installed carrier bearing sounded like a bell when I lifted the truck and put it in drive. The U-joints have also been replaced and the drive shaft will be off to be balanced once I get the brake thing figured out. Lastly, when I rotate the drive shaft without the tires or drums on it makes a sound at the hub like the brake shoes are rubbing but with the drums off. Is that a sign of something else going down hill or is that normal?

If you have any thoughts on any of this I'd love to hear it. I'm a little tight on cash and can't just throw money at it until something works much less a trip to a professional.

Jeff

 

define the pulsation, in the pedal and wheel? or do you feel it in your seat?

 

Does it stop and stop well just the pedal pulse a little?
Both my 94 and 96 have/ done and do it. The 96 will stop really well so I don't worry about it.

 

It seems to only be felt in the seat.

I did find that my emergency brake cables were a little sticky. I could fit my forefinger between the stop on the lever and the backing plate of the shoe at first. Now that I've pried the levers out, lubricated the cables the best I can without removing them and worked the pedal a bunch it is a bit better. The stops are still not touching the shoe backing plate though but it is now half of the distance than it was. I wonder if the springs on the cables in the drums are tired. Can you replace those separately or do you need to replace both rear cables to do that. That may explain the warping of the original drums I guess.

After spending all morning in the garage I'm still at a loss.

Jeff

 

A pulsing peddle is most likely: Rotors or drums that are out-of round. Since you have new drums, did you have them turned? Same with the front rotors. If the pulsing is slight just let it go....no big deal, if it shakes the tar out of you that is a problem.

 

That sounds like a bad axle bearing.
If the axle bearing is bad enough, the axle shaft/hub will have an eccentric motion/vibration, and try to walk in/out.

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I didn't have the new drums turned but I may end up taking them in just to make sure everything is okay positively. I am not feeling the pulsing through the pedal though and I've had the warped disk thing twice and it does not feel like that at all.

The wheel bearings is an interesting thought. Why would you suppose I only feel an issue when I'm braking though?

Jeff

 

That is the only time there is communication between the rotating Drum and fixed position axle housing.


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One last question......am I correct that there shouldn't be any noise at the axles or pinion when I rotate the rear end without the drums installed? It's making a noise like the drums are still installed at all three points like a shushing noise. Maybe the whole rear end needs a going through. I've been thinking forever about changing to a lower gear ratio for some better mileage. I have the 4:10 or 4:11 ratio now, can't remember the exact number, and don't haul anything that serious. At the speed I drive on the highway I don't get any better mileage there than I do around town. I get around 18 mpg everywhere. The truck is a 2wd, long bed, crew cab.

Jeff

 

I can't answer that.
You need local hands-on diagnostic help, to avoid wasting money.


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Hey, I'm back.....

I'm still having issues with this truck mostly due to lack of time to work on it. At this point I'm starting to drink heavily due to the pulsating and vibrating......at least that's my excuse this month I realize I have multiple problems but the pulsating on braking is the one I want to attack first. It was suggested above that the issue might be real axle bearings being bad. Is this something you can tell by trying to move the axle around looking for play with the drums off or do you pretty much have to remove the axle to find out? I can't imagine it's too bad because I'd expect some fluid leak arounf the seal if it were. I've got a new set of brake drums and shoes but I'd like to check the axle bearings if it's not too big a hassle. The first set of drums I got did turn out to be out of round from the factory. I had them machined and it helped a bit but the pulsating is still there. They might just be too bad to be fixed.

I also am having a problem with the bushing in the trans tail shaft housing. It makes a high frequency vibration at the hump between the drivers and passengers area. I replaced it once and it improved but it went out again after about a year. The last one I put on wasn't even tight right after the install. I may need to try a bushing from the stealership. Can anyone think of any other reasons I'd be going through bushings so fast. The original lasted over 150k miles.

I also replaced the ujoints and the center carrier bearing. I then was unable to find a place to balance it where they didn't have an issue with the center carrier bearing being a trapped type. I also realize that this is contributing to the high frequency vibration but could it also have anything to do with the pulsating on braking?

Jeff

 

Have you check the front brakes ? If the rotors are warped it would cause pedal movement and vibration

 

I've had the front rotor warp before and this doesn't feel anything like that. Nothing comes through the steering wheel.

Jeff

 

I just thought I do a follow up on my probem with pulsating brakes. I went through the rear hubs, brakes and did new U-joints along with balancing the drive shaft. The drive shaft balancing did help out with the high frequency vibration I was getting in the floorboards but the pulsating on braking didn't change a bit. Though I never felt a thing through the steering wheel I decided to check the front disks and sure enough the runout was .005 and .006. I popped for a new set of rotors and brake pads at Napa and my probem disappeared. As I said above, I've had warped disks on this truck before but you coud always feel it through the steering wheel. Not on this one. I didn't feel anything there what so ever. Oh well, it was an expensive lesson but it's done now. I just wish I could have spent the wasted money on some of the mods I'd like to get started on.

Jeff

 

Getting rid of the driveline vibration was not wasted money.
Glad to hear the pulsation is gone.

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