Picked up a 90 f250 last spring and have done a ton work to it. I'm at my last major issue (hopefully). The issue, squealing left rear brake. Everything is new both sides, shoes, drums, wheel cylinder, springs, adjustment screw etc. I have greased the contact points with the shoes and backing plate. I have bled the lines including the rabs valve. The left rear still squeals when the breaks are applied. I can't seem to find a whitness mark of any kind that could lead me to some weird contact issue.... It seems to be mechanical but I'm not ruling out hydrolic. Any ideas? Thanks

 

Have you checked the bearings?

 

Bearings seem fine, inspected when I installed new axle seals

 

When you press harder on the brake pedal, does the noise stop? Or get worse?

 

It goes away if I press hard enough, how ever I need enough speed. So town driving it will always squeal.

 

Try a new set of shoes.

 

Get a set of the cheapest brake shoes you can find, replace the side that makes noise. It if stops making noise, good, and you have a spare pair of brake shoes. If it still squeals, you have not tied up a wad of cash in the SUPER HIGH PERFORMACE "guaranteed not to squeal and they always do" brake shoes that the parts guy will try to sell you.

On my cars I all ways use the EXTREME DUTY brake pads like police cars use on the front, never had any problems of any kind. They cost more and have to be ordered, but are worth it. just
my 2cents..

 

I'd say glazed or contaminated shoes...

I'd try to gently sand the shoes and drum and use brake cleaner to clean the drum.

Or like stated earlier replace the shoes... but honestly I bet there just glazed or contaminated... light sanding to remove glazing is all that normally needed.

 

I’m thinking along the same lines as goodb0y, except I don’t think it’s glazing.

I’ve seen new pads and shoes alike (usually ceramic but semi-metallics occasionally have this issue) chip on the edges and create what is effectively a squeal tab when it happens. There’s not enough strength for the lining to actually cut into the drum and leave a mark, but it acts just the same.

Pull the drum and inspect the edges for chipping. Even if you don’t see anything, try sanding the edges just enough to remove the sharpness (shouldn’t need to remove shoes for this - pulling them away from the backing plate should be more than enough room), then thoroughly clean them and the drum.

Adjust both sides out until there’s a small amount of drag, then burnish them by slowly applying the parking brake at less than 20 MPH. Hold the release lever so they can’t get stuck on and use the parking brake pedal to apply the rear brakes for about 5 second intervals spaced 10-15 seconds apart. Repeat 5-10 times then drive normally back to your driveway and allow them to cool for about an hour.

The reason for using just the parking brake is because of the metering/proportioning valves - under normal driving the rear brakes only do about 20% of the work. In order to properly burnish them, they need to get hot and stay hot which is more difficult when there’s not as much force being applied.

 

If noise stops when you press harder, then it is glazing. Since you just replaced the shoes and drums, could you perhaps have the wrong shoes, ie, not matched to the drums?

 

Thanks for the suggestions, I have previously tried and inspected for all you guys have mentioned. That is why I turned to advice here. However, I have fixed the problem! The high dollar shoes I bought just did not work. I bought another set for half the price and no problems. A mechanic friend of mine said the number one mistake a mechanic can make is assume the "New" part they installed is good. Not sure if I 100% agree, but it sure rang true in this case.

 

I have a friend that owns a very busy NAPA repair shop, quite often the new parts he gets are of low quality or have defects. Parts that are sold by napa, advance, auto zone, orielleys, are now made offshore and often are just no good, even being brand new.

 

You don’t actually believe all the parts made for OEM are manufactured in the US, do you?

 

No, did I infer that? Are you wanting a pissing contest?
copy paste from above.---
--- Parts that are sold by napa, advance, auto zone, orielleys, are now made offshore and often are just no good, even being brand new.---

 

New OEM axles and transmissions have a huge amount of foreign parts in them. The problem is the few US made parts are no better, and many times worse, than the China and India parts.