Knocking noise....can't figure out...Help!

[Big Blzn]

OK, Fellas. The problem I have is that when I am driving my '72 around town I notice that when I come to a stop and press on the brakes I feel and hear a kind of knock noise that sounds like it's coming from the right rear. It doesn't do it when I first lightly step on the break but several seconds later. I think I also notice it a bit when I begin to take off from a stop but is kinda hard to hear with the roar of the engine and being that I have a full vert with no top on. I liken the sound to a golf ball rolling into the front of a truck bed when you brake and then into the tailgate when taking off form a stop.

I checked all the suspension bolts, checked the driveshaft ubolts and ujoints, body mounts, etc. and everything seems tight and fine. The blazer seems to brake and stop fine too. Is there something in the drum brakes of my 12 bolt that could be loose and making the noise? Haven't taken the wheel and drum off to see. Last I checked the R&P seemed fine but I do have one wheeling trip on them since I have seen them. It's not a big worry for me as my rig seems to drive fine but the noise is starting to make me more suspicious. Anything you all can think of that I may have missed?
Thanks, Hoby

 

[throttleissues]

So take the golfball outta the back, Hoby! Jeez!! You might be losing a wheel bearing. You are talking about the 12b, right? I didn't figure you put in the 14bff yet. The axle rides right on the bearing and can get the drum off center when the bearing goes south. Might wanna pull that wheel and drum, and maybe have a look at the axle and bearing, too. It's easy, you can handle it.

 

[tRustyK5]

Busted baffle in the gas tank? I had that with an old POS once...definitely more noticable as the fuel level dropped.

Rene

 

[bp71k5]

No baffles in the tanks that old, but maybe part of the sender. Does the gas guage read correctly?

You might try having someone sit in the back while you drive and try and pinpoint where the noise is coming from or at least narrow it down.

 

[toomany]

Do you have a tail pipe back there? The one on my Jeep broke off and was dangling by the hanger. When I'd stop, it'd bounce off the body.

 

[Big Blzn]

So take the golfball outta the back, Hoby! Jeez!! You might be losing a wheel bearing. You are talking about the 12b, right? I didn't figure you put in the 14bff yet. The axle rides right on the bearing and can get the drum off center when the bearing goes south. Might wanna pull that wheel and drum, and maybe have a look at the axle and bearing, too. It's easy, you can handle it.

Chris. Any special tools to get the bearings out. the shop manual I have shows a bearing puller and seal puller. Not worried about getting the seal out but what about the bearing. What would I look for in a bad or worn bearing. Should I be able to lift the axle flange up and down and back and forth with a lot of play in it to see if the bearings are toast. Also, would there be discoloration from the bearings being too hot? Or should it be tight with little play. I'll check it this week sometime.

 

[throttleissues]

The axle gets discolored or pitted early in the failure, then gets a groove and chunks peeling out of it from the metal sticking to the bearing rollers. I had one a long time ago that started dragging the brakes and clunking the shoes from the drum being so far off center. We'll address the bearing removel if you need to. So far, you just need to pull the axle and look at the axle and bearing. I was guessing axle problem since I figured you looked around at all the visible stuff, and I've had really weird noises from axle bearings. I've killed a LOT of them in cars and one 1/2 ton pickup over the years. I came to the conclusion that canyon racing is hard on axle bearings in my Chevelle or Cutlasses.