620 Drum Brake ??'s

[Willdatsun]

My (UK spec) '78 620 has two wheel cylinders in each drum, and I think it has cam adjusters. Oh and it has balljoint front end not kingpins.

[ggzilla]

Yes, 1978-1979 620s have balljoints and disc brakes.

[metalmonkey47]

FSM suggests when 1 brake is dragging, a possible loose wheel bearing is suspect? Is this probable? It would be very strange for the brake hoses to be the culprit, since this problem wasn't present prior to changing my front shoes...

 

I grew up with the understanding that generally when something breaks on a car, its because of something that has changed... everything on that drum changed but still isn't working.. I need to pull the wheel apart again and inspect it.

 

The brake hose looks like it's only a year or so old. The crimped metal connections are even still shiny.

[Guest kamakazi620]

FSM suggests when 1 brake is dragging, a possible loose wheel bearing is suspect? Is this probable? It would be very strange for the brake hoses to be the culprit, since this problem wasn't present prior to changing my front shoes...

 

I grew up with the understanding that generally when something breaks on a car, its because of something that has changed... everything on that drum changed but still isn't working.. I need to pull the wheel apart again and inspect it.

 

The brake hose looks like it's only a year or so old. The crimped metal connections are even still shiny.

Did you turn the drums???

[ggzilla]

Your logic is good. Now to find the cause.

[metalmonkey47]

Did you turn the drums???

 

No, the driver side drum was brand new about 6 months ago, so I didn't feel like taking it to be turned

 

Your logic is good. Now to find the cause.

 

:thumbup: Good logic is nothing without positive results :yawn:

 

Anyways, here's a video I just recorded. You can see exactly what I'm dealing with. It's still processing, so it may be a minuet before you can watch it.

 

http://youtu.be/cMITXtWR02Y

[bananahamuck]

Have you tried switching drums side to side if the problem moves to the other side, maybe it is a manufacturing flaw in the new drum...I usually turn the drum for good measure ..especially if it is new..

[metalmonkey47]

Not a bad idea. My shoes were 50% when i replaced it, so maybe the drums not fully up to spec.

 

I'll try that tomorrow and see if it helps.

[Eagle_Adam]

No, the driver side drum was brand new about 6 months ago, so I didn't feel like taking it to be turned

 

I was told even new drums "should" be turned. I got mine turned this time around and WOW, even if the look good and strait they may not be. Mine deff weren't :rofl:

[metalmonkey47]

SO I swapped drums on the front and the problem stayed at the driver wheel so I know that's not the drum this time.

 

I also pulled the shoes/adjuster out and it spins freely, so I know that it's 100% brakes.

 

 

 

This is what the inside of the the brake media on the rear(trailing) shoe looks like. Pretty obvious that's where it's hanging up right?

 

That begs the question... what would cause it to hang up on the inside of the shoe?

 

[datsunaholic]

Bent backing plate will do that (makes the shoe sit crooked). So can worn out wheel bearings/bearing races (since it moves the hub, and hence the drum, in closer to the backing plate).

[metalmonkey47]

I don't feel any play in the bearings, but it wouldn't take much for that to be a probable cause would it??

[metalmonkey47]

Abnormal Bearing play???

 

http://www.youtube.com/watch?v=LBCQOw21Yi4&feature=youtu.be

[Guest kamakazi620]

SO I swapped drums on the front and the problem stayed at the driver wheel so I know that's not the drum this time.

 

I also pulled the shoes/adjuster out and it spins freely, so I know that it's 100% brakes.

 

 

 

This is what the inside of the the brake media on the rear(trailing) shoe looks like. Pretty obvious that's where it's hanging up right?

 

That begs the question... what would cause it to hang up on the inside of the shoe?

 

By the oic i would say you have a bent backing plate or something cause'n the shoe to sit crooked...

[mklotz70]

Do you still have the old shoes? I'd compare them very closely and see if there's any difference with that trailing shoe. Width, length. Is the friction material flat or is it swollen on the inside where it's rubbing? Is the old one worn more on that inside area?

 

This is a bit more work, but you might try changing that trailing shoe to the other side of the truck.

 

Also, run that adjuster the rest of the way in since you have new shoes on. Put the lug nuts on the drum without the rim. Still rubs? Push the brake pedal firmly and release to center the shoes/adjuster in the drum. Rubs?

 

You could also use a sharpie and draw some lines inside the drum to see if it will scuff the line off where it rubs. That may show if the drum is out of round. Make sure to have the lug nuts on the drum before spinning it.

 

The old shoes probably wore enough that they didn't rub.....so the PO didn't bother with it. Or....the damage/problem happened after the shoes were worn enough so it didn't show up until it got new shoes. The new shoes may be slightly different.

 

When it rubs, does it rub evenly through the entire rotation or on and off? If on and off, it's most likely that the drums need turned....new or not. You have to think that this is cast steel that may have been made 30 years ago and has been sitting on a shelf. No telling if it sat flat or on edge. Most parts stores will do a clean up cut on new rotors or drums for you when you buy them from them. Rotors can have the same problem. The parts store guy thought I was nuts when I asked him to do it....until I came back a couple hours later and he rather sheepishly told me that one was really close, the other definitely needed a shave. Anyway......

 

As 'aholic said.....it could be the backing plate is bent which is more likely than a bent spindle. When you have the drum on loose, it shifts a tiny bit so that it doesn't rub bad enough to be a problem, but when you tighten the drum down, it pulls it flat to the hub and if the backing plate is skewed, it rubs. Bad bearing play would let it turn too until the rig was on the road, then it would drag......but you don't have this problem and your bearings are tight. With the adjuster all the way in, it should not rub. If the rub is even all the way around, the drum is true(perfectly round) and the shoes is out too far. If it rubs in one or two spots, it's warped and needs to be turned. Since you know it's the back shoe that drags, mark the drum at the part with it rubs the hardest on the rear shoe. Take the drum back off and measure the inside diameter at that place and then also 90 degrees from that. Are they identical? This is only if the drum is rubbing off and on...not constantly the same. If it rubs off and on, it's likely that both of your drums are out of round....which is why the problem stayed on the driver's side....or seemed to. The pass side has the shoes backed off enough that it doesn't rub.

 

Back in the day, they would grind/sand shoes to fit the drums. I don't think anyone can even do that anymore.

 

If it starts rubbing after you push the brakes, but was fine before, the adjuster is not sliding back to center in the backing plate. I know you said it moves nicely....just throwing that out there since I'm here.

 

Okay....there's several options and some cover the same stuff. Basically, if it rubs evenly, the shoes are out too far(adjuster) or the plate may be bent. If it rubs intermittently, the drum is out of round...it's the only thing rotating.

[Guest kamakazi620]

Not a bad idea. My shoes were 50% when i replaced it, so maybe the drums not fully up to spec.

 

I'll try that tomorrow and see if it helps.

Did you replace 1 drum or both of them???

[mklotz70]

That's fairly normal bearing play. How much it moves outside of the hub isn't important. The bearing play you would be concerned with is hub movement when mounted. Basically....the spindle nut would be too loose. When you take the dust cap off, wiggle the hub up and down and see if it moves in relation to the spindle. If yes, nut is too loose. If not, you're fine....provided the hubs spins nicely and the nut's not too tight.

[metalmonkey47]

Ok, so here we go.

 

The drag is even for the entire rotation of the drum. I can't seem to find ANY physical evidence of anything dragging except the shoe on the drum. In fact, upon closer inspection I found that the leading shoe had slight signs of heat scoring where it was dragging too. Strange thing is that the truck even pulled to the right, even though the drivers side was where it was already dragging.

 

Comparing the old shoes to the new shoes I really found no physical difference. What I'm going to go ahead and do for now is swap the old shoes back onto the truck until I can find a reason as to why they'd be dragging.

 

 

 

Here are a few pictures of the old shoes and etc.

 

 

OLD SHOES:

 

 

 

Bent backing plate is probably it. I imagine someone probably tried to pry against it to get the drum off. It looks perfectly round, but who knows right?

[metalmonkey47]

So I swapped the old shoes back onto it and it STILL drags. This is driving me crazy. It didn't do this before I changed the shoes, and putting the old shoes back on didn't fix it, so it must be something I did while working on it?? that seems to be the only common variable.

[mklotz70]

Will that adjuster go in anymore?

 

I snapped these this morning to compare with your pics to make sure that small spring was correct.....and yours are the same as these......but what I just noticed is that the shoes are backwards. No guarantee that mine are correct, but as you can tell, they've been unmolested since removal. You might try swapping them.

 

 

 

[metalmonkey47]

The adjuster still had a few turns to go in, but then I literally have no brakes and my pedals gone soft. (Interesting right)

 

Definitly going to try flipping around the shoes right now.

[datsunaholic]

I know this has been covered, but when adjusting, you tighten the adjuster until the brake is just starting to drag, then push and release the brake pedal. Doing this centers the shoes. The shoes will normally, on at least the first go, become loose (not dragging anymore). Then repeat. Do this until pushing the pedal doesn't change the amount of drag. If the drag INCREASES after pushing the pedal, you have a problem with fluid not returning, but I don't think that's your issue.

 

Now, after you do that, drive around the block and stop several times (but not HARD). Then do the whole readjust thing again, because they take a set. I do this and I have great brakes, until the next oil change when I need to adjust them again. Good quality shoes sometimes last 2 oil changes between adjustments. The older the shoes the longer the interval because they set in to the drum.

 

Looking at your old shoes, you definately have side wear on one pair. That's caused by shoe/drum misalignment which is as I said before caused by a bent backing plate or loose wheel bearings. Someone mentioned bent spindle too and that's possible, though I'd think youd be burning up bearings if that was the case,

 

BTW, even with all that I had a similar issue with new shoes "dragging" the drum. I just had to let them wear in a bit- they were nice new shoes but an old drum, and that made the drum radius just a tad too big for the fresh shoes. Unfortunately I bought crap shoes, as they are cracked to hell in just a year (25,000 miles, but a lot is stop-and-go). I will replace them once I locate my adjuster tool.

[Figbuck]

I fought the 620 brake wars for... uh, decades?

 

The best thing I ever did to my truck... the best thing that has happened to me in like five years, was getting the Klotz Midnight Performance front disc treatment. Period.

 

My Dad use to tell my brother and me this story... (sorry if you already heard this, but I heard it a million times):

 

There was a guy named Simple Dill who used to go around hitting himself in the head with a hammer all the time. One day I ask him, "Simple Dill, why do you go around hitting yourself in the head with a hammer??

 

Dill: "Because it feels so good when I stop!"

 

That's what it was like to loose the drums. Every day I get into my truck and smile when I put on the brakes!

 

Hey Mike... you know I was telling you that I hadn't been able to lock the fronts up yet? The other day some clown in a BMW decided to cut me off before an off ramp at about 55 or so, just as the stream of traffic totally checked up. I stomped on the brakes as hard as I could to keep from hitting him. It braked straight and true, scrubbed off speed like crazy... but I was having one of those, 'Oh shit I'm gonna to wad this thing up moments!"

 

Both front tires chirped big time, I'm running 225s and that is a lot of meat on a clean dry road. It wasn't a screech but a nasty growl. Then they hooked back up and saved me! It happened so fast. It never pulled and braked in a straight line.

 

It seems to me that I never had any issues with my brakes until way into the '80s. I used it as a freeway commuter, hauled trailers full of fire wood and concrete buggies that weighed as much as the truck. I don't remember having any problems with brakes and it was easy and straight forward to do a brake job and adjust.

 

But I also remember that when you bought shoes, there were leading and trailing pairs. In the '90s it seems like they they were all the same and interchangeable. That is when I started going through all the same stuff with pulling and constant adjusting.

 

I always had new drums turned. A couple years ago I did new drums all around, replaced two sketchy cylinders & new master. should have worked like new. They sucked. I found a Datsun jack just like my OEM jack in a dumpster, so any where I was, I could whip out two jacks and have the front in the air in two minutes. It should be easy to spin the wheels until they lock and then back off two or three clicks or something.

 

It just wasn't working because they pulled all the time. I spent a whole day driving around my neighborhood trying to figure out how to dial out the pull. I never really understood what happens.

 

When it pulled right, I backed off the right wheel a couple clicks and tightened the left one two clicks, thinking that a tight right made it pull right. That seemed to make it pull even more to the right. I began to think that tight right pulls to the left or tight left pulled to the right. I would drive around and then it would just start pulling to the other side... sometimes even "hunting" left and right. This was after enough miles to have bedded that shoes in...

 

Finally I found a street with a very slight grade so I could push the truck and make it roll and stop with one finger. I got under the front and clicked until it wouldn't roll, then I backed off until it was free enough to roll. You can tell within one or two clicks if they are locked up or free. That seemed to be the best I could do. It worked around town, but at freeway speeds it was so freakin' hairball scary. I drove around for two years with the attitude that I just didn't have any brakes.

 

MM, I feel for ya bro. This shit sucks. What a waste of time. It's not like the thing is alive. It doesn't get sick or heal itself. It's a finite hunk of metal subject to physical laws. These trucks are so simple it almost never fails that problems have simple solutions... except for drum brakes?? Black art.

[datsundash]

Whatever you do when working on your brakes make sure and TIGHTEN YOUR FUCKING LUG NUTS PROPERLY!!! if you dont then your wheel may FALL THE FUCK OFF!!!! :w00t:

[Guest kamakazi620]

^^^ This shit is funny,My 620 drums work great!! im used to driving with NO brakes on a 620 E brake and downshifting............