I have a 98 F-150, 2WD with Limited Slip Rear Diff. It has disc brakes on the front and drums on the rear.

I have been having some difficult getting the rear brakes setup correctly.

Here is a brief history.

Within the last four weeks I have had the front brakes done. New Rotors, pads and caliper rebuilds. I had a thumping in the pedal and this completely addressed the problem.

What I have going on now is under moderate braking, I get a vibration from the rear end. I have the drums checked to see if they were out of round and they are in spec according to the tech. The pads look good too.

The sensation I am getting is similiar to when I had my e-brake lock up and drove for a few km's before I realized it. At that time the truck started vibrate pretty good, coming from the rear.

I adjusted the rear brakes about two weeks ago, and all appeared to be fine.

It has gotten quite warm out lately and the problem is back.

My only theory at this point is that I have the adjusters done up too tight and the rear brakes are overheating. I am going to back them off and see if this helps.

Any other advice is appreciated.

 

I recommed having the drums turned. This will get rid of any rear pulsing. They may well be in spec., but out enough to give a vibration. Don't rule out that the rear tire balance or out of round could be causing a vibration as well as a u-joint ot a bent drive shaft. Sometimes new guys bend the shafts while lifting trucks by accident with hydraulic post lifts.

 

I agree, assuming they won't go out of spec afterwards, resurface the rear drums. My dad's '97 would vibrate as if driving over rumble strips, turned the rear drums and put shoes on it (which it needed anyways) and it's been good to go since.

 

My guess would be the rear drums. One way to know for sure is to go into a vacant lot and go about 30mph and try stopping with just the e-brake, if it does the bumping, than get your drums turned. My 97 was having the same problem and I got the drums turned and replaced the pads and it made all the diffrence in the world. Funny thing is, it just started doing that after I changed my fronts also.

 

New brakes on one end of the truck tend to exaggerate any problems on the opposite end.

 

The e-brake trick I already tried. There is no vibration when I do that.

I also do not get the vibration all of the time, which I would expect with out of round drums. I would also expect the problem to be worse at high speeds, much like is was with my bad front rotors, but this is not the case.

It has me quite puzzled. I backed off the adjusters yesterday, the problem did not occur on my test drive after.

I will see how it goes the next couple of days when I start driving the truck more again.

If all else fails, I will replace the rears brakes.

 

Before you replace the shoes, look closely at the rear axel seals. If a little oil got on the shoes, they will act up and grab only when warm/hot, not cold...If so replace rear axel seals/bearings before changing shoes.(most rear axel seals go bad because the spicer/dana has such loose tolerances on their bearings....by replacing with a good timkin or TRW, your axel seals will probably never leak again).....good luck.

 

I forgot to mention I did have the rear axle seals replaced at the same time as the front pads/rotors as they were leaking.

I have now also replaced the rear drums and shoes. Things were OK for a week or two and now guess what, the rear vibration is back.

If I put the e-brake on while moving I also get the vibration so I guess my drums must be out of round again.

Other opinions? What would cause the drums to go out of round so fast?

 

This may sound dumb...but here it goes. Did you apply your e-brake after getting your new rear brakes warm/seated. This can easily cause a new drum to warp. Just a thought. If so, re-turn the new drums and re-install. Give it a while of seating in and getting warm and cool (couple days) before applying the e-brake.

 

The drums I purchased have a two year warranty. A new set is on the way. I will install later this week and see how that goes.

 

The plot thickens....

Tonight I decided to jack up the back end and check to see how the rear brakes were adjusted. I wanted to ensure the right and left auto-adjusters were both working and keeping both sides approximately equal.

This all checked out OK, with the drivers side just a tad bit looser I believe. I then pulled off the drivers side drum to perform a visual inspection and everything looked good. I tightened the adjuster on this side (drivers) about one tooth worth on the notched wheel.

I put it all back together and then ran the truck in reverse on the jack stands. The brakes worked fine with multiple attempts. So far so good.

Now is where it gets interesting....

I then put the truck in drive and gave it a go. The brakes worked fine the first couple of stops. Then the drivers side started to act up. It would not stop "normally". I could push the pedal in for most of it's travel and the drivers side wheel would not stop spinning. As I held the pedal down I would feel two to three distinct steps down in the pedal as the brake appeared to tighten to eventually stop the wheel. It did this at least three time in a row, getting a little worse each time. The final attempt would not stop the wheel at all and I believe I reached the end of the pedal travel. I don't know what the passenger side was doing at the time.

I then put the truck back into reverse and tried it several times. Everything worked fine. Wheels stopped as normal.

Now a little confused, I put the truck back into drive and could not repeat the problem. This was not from a lack of trying, believe me. I tried back into reverse then drive multiple times but could not get the same thing to happen. Nothing worse than an intermittent problem....

So any ideas? Should I be concerned?

 

New drums are on the truck and I still get a vibration from the rear under some breaking scenarios, not all. I don't believe it was the drums causing it.

I notice most under "moderate" breaking. Light or heavy pressure and all is fine.

Any ideas?