I think I broke it already

[oldbee]

Yup, it’s all pretty new, low mileage. Still thinking rear bearing. Time for a little more time on that wonderful thing known as concrete,yuck.

 

[Cornpatch MO]

Thanks, Mo. Yes, it does have a definite "geared" sound to it. No, I haven't gone to the speedo drive yet - I figured if it was something like that, it surely would have chewed the plastic off the speedo gear pretty quickly? It sure is persistent and predictable - and sort of heavy for plastic? I dunno.
As far as your other suggestions, all that jazz was checked before, checked today. Total waste of time in this particular case. Why? Once again - this is a SUDDEN occurrence and all of those are gradual wear items.

I have heard a similar sound before in something I had . But 50+ years of lots of different machinery----I can't recall What all else in the transmission is always at the speed of your output shaft. Keeping in mind that your complete differential including axles and wheel bearings are at that speed.
I once had a big truck that I was convinced there was a tooth off a gear in the 13 speed tranny. you could hear it and feel it in the shifter. Took out and dis-assembled it--no problem there. Turned out to be the front differential. Wasted shop time really cost me...................MO

 

[moparedtn]

I have heard a similar sound before in something I had . But 50+ years of lots of different machinery----I can't recall What all else in the transmission is always at the speed of your output shaft. Keeping in mind that your complete differential including axles and wheel bearings are at that speed.
I once had a big truck that I was convinced there was a tooth off a gear in the 13 speed tranny. you could hear it and feel it in the shifter. Took out and dis-assembled it--no problem there. Turned out to be the front differential. Wasted shop time really cost me...................MO

See, that's what makes sense to me as well, at least in this case - the way the noise manifests itself in conjunction with only the actual vehicle speed and nothing else tells me it's nothing to do with anything forward of the tailshaft section of the transmission - I think.
If that's the case, we aren't talking about many possibilities here, especially possibilities that sound like a gearing issue:

There's only the main output bearing, the speedometer gear drive, the mounted shifter and the tailshaft bushing & seal in the extension housing.
To me, that only leaves the bearing and the speedo gear setup as possibilities?
I'm hurting pretty good this morning from all that concrete rolling yesterday (heavy rain has set in too, which isn't helping), but once it warms
up a little today I'll get back under there and pull the speedo gear out for a look.

 

[440+6]

You sure the driveshaft isn't rubbing on the exhaust, when up on stands the shaft will drop and not rub?

 

[moparedtn]

You sure the driveshaft isn't rubbing on the exhaust, when up on stands the shaft will drop and not rub?

No, but I'll double check when I'm under there again.
When I had it up on the 4 stands, they were under the axle, so the suspension, body, etc. were at "normal" ride height - and therefore, the driveline was at its' normal angle and the exhaust was at its' normal relationship to everything.
Think of it as driving constantly downhill. Only difference was the wheels themselves weren't bearing weight.
Thanks!

 

[moparedtn]

*sigh* Nope....

It looks new, like it ought to since it is.
EDIT:
I'm going to slap it all back together and just leave the speedo cable unhooked so that the fluid stays in the tranny, just to eliminate the cable.
Hail Mary for sure, but I want to exhaust the last of the possibilities.

 

[PP1RT]

Drop it out and open the side cover. Only out some time and a few dollars in materials at this point.

 

[Cornpatch MO]

No, but I'll double check when I'm under there again.
When I had it up on the 4 stands, they were under the axle, so the suspension, body, etc. were at "normal" ride height - and therefore, the driveline was at its' normal angle and the exhaust was at its' normal relationship to everything.
Think of it as driving constantly downhill. Only difference was the wheels themselves weren't bearing weight.
Thanks!

Ok , really reaching out there, but, jack stands under the axle, no weight on the wheels, no noise. Noise when driving down the road ---possibly makes the noise after you have applied the brakes? However , I would think you could tell noise from that area.............................MO

 

[mopar 3 B]

No weight on wheels and no load on drive train no noise. Only a few bearings affected and the noise comes back.
Time to get the stethosope out for a good listen. Not that hard to hear the difference between a good bearing and bad.

 

[moparedtn]

Ok , really reaching out there, but, jack stands under the axle, no weight on the wheels, no noise. Noise when driving down the road ---possibly makes the noise after you have applied the brakes? However , I would think you could tell noise from that area.............................MO

No on the brake theory (tried, no difference) but thanks, my friend.

 

[moparedtn]

No weight on wheels and no load on drive train no noise. Only a few bearings affected and the noise comes back.
Time to get the stethoscope out for a good listen. Not that hard to hear the difference between a good bearing and bad.

The clues are actually three-fold to me:
1. All at once after banging gears (rapid speedo speed change top of 2nd due to wheelspin)
2. No noise when car hasn't been driven at least a few miles - up in air or on road.
Once it's had a few miles above 45, it shows up (something getting warm/hot).
3. Not a perceived heavy gear type noise, as anyone with a good ear can tell listening to the video. This racket is much more
speedo cable-like (lightweight and reciprocating) and the location it is emanating from is VERY specific under the hump in the
floor - where no bearings are in the tranny, I might add.

I've got the it back together now and full to spilling with fluid again. I have intentionally left the speedo cable OFF.
When the weather allows again, I'll try that.
If that comes up fruitless, I'll just go into hock and get a good, known, built transmission from a reputable vendor with a
friggin warranty and be done with it.

 

[mopar 3 B]

I would find the cause before replaceing parts. Remeber last time?
If it has to warm up to make noise it must to getting hot. Temp gun may even find it

 

[PP1RT]

Or your hand. When you get back from the drive put it on stands right away and feel around?

 

[moparedtn]

If it winds up not being the cable, then it's something in the transmission. Of that I have no doubt - and since I know absolutely nothing about the unit, I'll wind up doing what I've done with the rest of the car - replace it with something I DO know about.

 

[NJRR]

If I read the thread correctly, you could not reproduce the sound when it was up on jackstands. You got the drivetrain and rear wheels up to speed, but not the front wheels.
Maybe it's a bad wheel bearing up front? Noise does travel. Just a thought.

 

[kiwigtx]

The pilot bushing in the crankshaft is gone

 

[bearman]

does the oil show signs of metal. rear bearing on tail shaft spinning inside the housing under load.
just guessing but under load and torqued up to road speed could be a binding bearing in the housing.

 

[moparedtn]

If I read the thread correctly, you could not reproduce the sound when it was up on jackstands. You got the drivetrain and rear wheels up to speed, but not the front wheels.
Maybe it's a bad wheel bearing up front? Noise does travel. Just a thought.

Thanks, but...
Did you watch the video?

 

[65Fury440]

Taking shotgun type help on the net is hard but..
I just went through this with my rebuilt 4 speed.
I was getting a vibration that was high speed related, but only on hard acceleration.
I had the driveshft rebalanced, it was just a lil out, no change.
New spicer joints, no play in pinion bearing, no play in tailshaft bearing (the ball n trunnion use a bearing, no bushing).
So finally I got some noise with the clutch pushed in. Tore the trans out, new pilot bushing was wallowed out.
I checked bellhousing runout, it was .002 out, not much.
I have been told, possible the paint on my trans and bellhousing may have combined to throw the alignment out enough to eat the bushing.
I would have bet the farm, that it was something in the output side of the trans. Good luck!

 

[moparedtn]

View attachment 575599
The pilot bushing in the crankshaft is gone

Hmmm. Seems like someone said that early on in the thread.
Oh yeah - that was YOU.
(Sorry, don't have your flag handy. Canadian flag substituted.)

Seriously, if it was the pilot bushing, the noise would vary with engine (input shaft) speed I'd imagine.
It's not coming from the bellhousing area anyways.