Here is a tough one for you:

Drews 74. Front disk brakes. He is getting an odd sound - kind of grinding, kind of moaning - whum whum whum... Not a thumping more of a rubbing sound. It is a consistent sound - speeds up when the car is moving faster but is not the same as tire rotation speed. When traveling at Highway speeds it is making the whum-whum-whum sound about 2 times a second. The tires are turning many times faster than that. When moving at 20 miles an hr it slows down to once every second or so.

Seems to be coming from the front end - but not 100% sure. Hubs are not overly hot after traveling from Yankee Hill yesterday....

strange.

Thoughts?

Update: Last nights developments

Not much of an update here.

Replaced the outer bearings - still makes all the same noises.

whum-whum-whum-whum: Seems to be coming from the front but can not really tell

Clunk: Mostly when turning, cant really tell where it is coming from but you feel it as much as you hear it. Sometimes when shifting, accelerating, but mostly turns.

Drew is off school today early so first thing he is going to swap the tires out for some miniature donuts Landshark loaned me for my build. Just to see if perhaps tires could have anything to do with things.

Then - start replacing U-joints.

One thing I noticed last night - checking things over. We placed the bronco up on jack stands and I had Drew "driving" it in place, shifting from drive to reverse (yes stopping the tire spin first by applying the brake), bringing it up to 30-40 mph and watching things underneath. When it reverses from D-R and R-D, there seems to be an excessive amount of slop or movement at the T-case output shaft. Of course there is some movement at the axles - which I attribute to backlash. And I was not able to duplicate the noises with the tires in the air... Of course he was not turning. What is excessive you ask? I don't know, perhaps if it was a clock - 5 minutes at the most. Could be closer to 3 minutes. I do not think this is the same clunk we are hearing when we are turning.

On the bright side - we did discover that the steering box is still flexing on the frame despite much welding and bracing so soon - as in very soon - there will be an additional cross member in front of the steering box connecting both frame rails. It was too late last night when we discovered this. If I pulled out the grinders and saws at 9:15 pm on a week night in a neighborhood couldesac where numerous school age children reside.... well I might just lose my favored neighbor status...

Can you borrow a set of tires? I know you said it didn't appear to be that, but that's an easy try. Are the tires cupped at all? It may be such that with centrifugal force, that the spot hits every other turn? You would think you could feel that, but maybe not.

I am no expert on the D20, but that amount of slop seems normal for a 40 year old t-case.

Clunks - make sure rear axle u-bolts are tight on the leaf springs. Check leaf spring bushings, then check ball joints.

JD,

Thanks for the ideas. Yes - Drew will put on the "petite" rollers for my stretch build this afternoon, already have this planned. His tires are pretty darn new right now less than 6 weeks old.

Good call on the axle U bolts, damn I don't want to deal with bushings or ball joints right now. But those solutions seem plausible.

Thanks!

The clunk could be the noise from a bad trac bar bushing reverberating in the frame. I doubt it, but it'd be worth checking. I agree with JD that that amount of slop seems normal. Is there lateral play in the output shaft? Dumb question, but are the hubs locked in and causing drivetrain noise?

Add to the "things to check" list: spin all the tires while up in the air (no launching it off a jump does not count) and look for a bent axle, spindle or rim.

Speaking of spindles - do you have much up and down movement in the axle shaft? Grab the axle at the u-joint and see how much movement you have. If it's sloppy the spindle bearing is likely bad. Could be causing the axle to move up and down enough that could cause the hub to rub. Hard to explain it but I've personally seen it happen.

Well folks, as I predicted, sooner or later whatever the mystery clunk was would reveal itself and on Friday morning.... it sure did. A puddle of oil that rivals the Exxon Valdez was found under the left rear tire in the high school parking lot. After seeking some advice we determined perhaps some seals and possibly maybe even a bearing might be on the parts list. So while i chased parts for him; Drew turned himself into the EPA for dumping of hazardous waste. Parts were sourced, disassembling did in fact reveal a toasted.......ok a destroyed rear bearing? and seal. Kinder is going to stop offering to help us soon. We were at his house at 0630 with bathtub sized cups of Starbucks coffee. Kirk. Walked us through the proces as he was not able to help. It seems that despite being pretty darn sure we had a regular old small bearing axle....nope. we have a large bearing axle. Back to the parts store with the axle in hand. Two stops later we have the correct seals and bearings. And a big old pipe on loan from Kirk. Off to the house.

Once there, drew decides that complete dissembly of the rear end would be wise, who knows how many bearring parts found their way past the deformed seal and into his diff, so out comes the other axle and center drop out. All good, no chunks.

Meanwhile, I grind a cut into the old bearing, cut it off, and use the big pipe and a hammer Thor would be proud of to "press" the new bearing in place.

Drew put the center section back in, then the passenger side and finally after a few tries, some cursing and turning of the other side... the drivers side fell in with a much more satisfying "clunk". Bolt everything up, oss on the tires an a test drive reveals....... nothing. No more clunks, no more leaks (from the rear end at least).

So what did we learn?

Whumwhumwhumwhum noise equals front wheel bearings.

Random clunk, especially prevelant while turning equals rear axle bearings....

That's good you found it where you did. A seized bearing at highway speeds can cause some bad things to happen. And another reason, I hate mud. May not have been your culprit, but damage caused by water and mud rear their ugly head weeks and months later.

You are real lucky. I had the pass side wheel bearing go out on me when I was coming back from college one time. I had a crap load of stuff in the back as it was Christmas break, so I was doing about 75 mph south down I-25 just north of the Water World exit and I heard an awful noise. It would happen every couple of minutes and then stop. I heard it 2-3 times then pulled over to look. Got out, walked around couldn't see anything on the outside, then crawled under the front, nothing...looked under the driver side rear, nothing, then the pass side. The tire & outer brake assembly was about 1" too far west. The only thing that stopped the axle, brake, tire & rim from barreling into the fencing on the side of the road was the fender. I was Luber'd at the time and thanked my lucky stars I was. The tire was hitting the fender and bouncing everything back into the axle tube. I called my parents and my dad drove up from the Springs and we loaded it on a trailer and we trailed the rest of the way home.

Not in my Bronco, but when I was a young man (17) I was running my '66 F100 back from Oregon to Colorado and I lost the driver side rear wheel bearing in "nowhereville" Wyoming, the back of the truck was full of all my possessions, including several hundred pounds of tools. Spent a cold night hunkered down until my sis could drive up from Denver to deliver the needed part. Just one of many lessons learned with that old truck.