What is this noise?

Mart said:
Short drive with proper loads being transmitted. shaft slowly moves forward, contact remade with trans bolt, noise reappears. Mart.
Click to expand...

I'm still listening and pondering.
I don't understand what you're talking about.
I don't understand what transmission bolt the drive shaft could hit to make the noise. The front end of the drive shaft is inside of the U-joint. How could it hit any trans bolt?

Yours is a new idea. Telll me more. I'm looking for anything that makes sense.
 
Henry Ford never spent any money he did not have to. I always wondered what the pins where for and I think you are going to find out for me. I do not remember the detail inside the U joint but I think there is a bolt holding it to the trans output shaft and that probably is what Mart is talking about.
 
I understand what you're talking about now and it's making sense. Wish I'd had that suggestion before I put everything back together. That would have been easy to check and fix if that was the problem. I'm going to do some more testing. If that is the problem then going up hill the shaft would slide back away from the bolt whereas going downhill or stopping it would slide forward and hit. So, I'll try to reverse the natural process by pushing in on the clutch while still going uphill and see if I've got the noise. If I don't have the noise pushing in on the clutch going uphill like I do stopping or decelerating downhill that will be more support for this theory. I'll also listen again under the car in the U-joint area to see if I can hear anything. The sound was all coming from the back before and I would think I'd hear something up at the front if that was the problem so I'll listen again.

Thanks for your continued support and ideas.

Funny thing. Strange new noises bug me a lot more before I figure out what they are. After I figure out what they are and know it's nothing too "serious" I seem to be able to tolerate them better. In this case, if it is a loose bolt holding the U-joint to the transmission output shaft I'll have to think about the consequences of waiting until it falls out verses taking it all apart again just to tighten the bolt. Or, maybe the bolt is tight and I just need to figure out how to get some pins to work in the coupler with all of the slack on the pinion spline.
 
old henry, you wrote - I just need to figure out how to get some pins to work in the coupler with all of the slack on the pinion spline. maybe you could use a smaller diameter pin, so there would be no shearing action with the lash between the coupler and shaft. i believe the pins are in there for a reason.
tom
 
Did the front end of the drive shaft or the head of the universal bolt show any signs of impact?
 
Yeah, redoing is PITA. Re-read post #58. That will be the solution to keeping the worn parts in the proper alignment. If the coupler or shaft is moving for and aft causing the noise. A modified pin will prevent the excessive movement of the coupler and drive shaft.
 
I didn't say anything about the bolt being loose, just the shaft drifting forward and contacting it.

Mart.
 
Henry:
If the shaft is moving I think it is sliding not by the fact of going up hill or down hill
AKA gravity
I think it is torque / acceleration torque pushes the shaft back wards , lack of torque it is pushed forward.
Try this try backing up the hill and see if you hear it,and also try going down hill forward and apply the brake and accelerate at the same time. see if the noise shows up.
 
It's very difficult to work out what is happening remotely.

Here's another scenario.

Due to the helical cut on the gears, when the car is being driven down the road and accellerating, the pinion is thrust forwards, away from the diff carrier. This puts the main load on the rearward pinion bearing.

When decellerating, the helical cut on the gears pulls the pinion inwards towards the diff carrier, putting increased loading on the forward pinion bearing.

You had damaged parts floating around in the area right near to the forward pinion bearing.

It is conceivable that the forward pinion bearing has been damaged or a flake of pin material has got in there. It may be this damage or contamination that is causing the noise. You don't hear it under power because the front bearing is only lightly loaded, it becomes louder on the overrun because on the increased load in that condition.

As I was typing I thought of a way to test this. If the front bearing is damaged, it will be noisy in reverse. Louder than on the overrun going forward. If it is loud when accelerating in reverse and quiet on the overrun in reverse than it could be the front bearing.

Or not.

Mart.

PS good cut away drawing of a diff unit on Mac Van Pelt's site.
 
Mart:

Kinda what I was trying to say but I guess Bottom line is it will not get better on its own.
It's like living under a one legged man going to bed you hear one shoe hit the floor but wait for the other / when will it happen / in this case when will it fail,the uncertainty would drive me nuts !!!!
 
One more diagnose before you repair story you might enjoy:

Several years ago I was coming back from a parade that I drove my car in and it died. No matter what I tried on the side of the road I could not get it started and had it towed home. For several weeks after that I tried everything I could think might be the problem and finally concluded that it just didn't have enough compression to run any more (it was 50 years old and had never been rebuilt). So, I concluded that was all that was left to fix it was rebuild it. I searched long and hard all over the country and finally found one of the best flathead rebuilders just 35 miles from me. I towed the car up to him and told him very plainly, "I don't want to rebuild this engine if it doesn't need it. Do everything you can just to get it started and running if you can before taking it out and tearing it apart." I thought I had his agreement on that and left. The next morning I called him to see how it was going. "We couldn't get it started so we've already taken it out and started rebuilding it." Well, after a couple of months it was finally done and I went to pick it up. It still wouldn't start!! And he didn't know why??? So, I towed it back home. As you know, when an engine is rebuilt they just take all the stuff off of it (distributor, coil, carburetor, water pumps, etc.) and set them aside and just put them back on when the engine is rebuilt without doing anything to them. And so it was with me. So, I got it home and then and only then did I decide to replace the condenser that I'd just replaced shortly before that fateful day coming home from the parade. It was about the only thing I hadn't checked because "it was just replaced." You can see where this is going - that was all that was wrong with my engine - a bad condenser!!??

So, there you have it - because I did not accurately diagnose the problem by checking all components by themselves before giving up I spent $3,000 to fix a problem that did not get fixed that I could have fixed for $10.

And now, after all I've said on this subject, I am just about to violate the principle and just buy this complete assembly of axle, torque tube, and spring that has 92,000 miles on it and was just removed from a driver for $500.00 to just totally replace eveything that just may be broke or at least badly worn. That's just $20.00 more than just buying a new ring and pinion gear. I'm at the end of my rope. I'm tired of messing with it and bothering all of you good people with this silly problem and have lost all confidence in my ability to diagnose on this one.

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What do you think of that idea?
 
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