8-3/4 open diff whining, wheels binding, pulled axle shafts, problem...disappears?

[cudak888]

My '68 Satellite saw the road today for the first time (that I've had it anyway). Almost immediately, the following issues made themselves apparent:

• Acceleration feels as if there's a load on the drivetrain, as if the parking brake is partially on.
• Anything over 10mph gets the rear end whining like a banshee.
• Shifting weight to the left of the car (right turns) would lessen the sound; shifting weight to the right would increase it.

First thought here was a ring and pinion eating themselves up, but I've learned long ago not to expect big and obvious noises to equal a big and obvious problem.

This said, I lifted the back end off the ground and found both wheels difficult to spin. They'd spin easily for part of a full revolution, then bind, then roll smoothly again. Then I started the engine and let it run off the ground:



While this looks like a brake pad dragging, it didn't explain the whining. Diff is full of fluid too.

I then pulled the axle shafts - left side, then right:

This is what I found, in order of discovery:

• Left shaft wheel bearing spins fine.
• With the left shaft out, the right wheel would spin and bind.
• Right shaft wheel bearing spins fine.
• With the right shaft out, the left wheel started binding through its entire run.

And here's where things got interesting: Even though the left wheel was still binding harder than I expected, the noise went away on the test drive I made immediately after reinstalling the axles. The feeling of friction holding back acceleration remained.

So before I make any assumptions here and re-adjust axle end play based entirely on the '68 shop manual, I wanted to run my theory by you fellows, to see if I'm barking up the right tree:

1. I have a suspicion that the end play was set too tight, and the act of pulling and reinstalling the passenger's side axle allowed play to be introduced into the system; perhaps the retainer bent a fraction of an inch while being torqued down? Perhaps it's not really bottomed out and just feels it by bolt torque? Worthy theory, or hogwash?
2. The last test ride still felt sluggish; as if something is dragging. Perhaps not only the end play is out, but the brake shoes are dragging as well. I'm pretty convinced of this myself, and it can't hurt to back down the adjusters all the way after I set the axle end play to disable the rear brakes for a test. Thoughts?

Thanks!

-Kurt

 

[RT K_line]

Did you check the bearings for smoothness when the shafts were out? If so then it sounds like your on the right track. Also you can check the pinion for excessive slack, with the trans in neutral move the drive shaft back and forth.
I usually adjust the rear brakes after assembly by pushing the parking brake pedal down 3 clicks then adjusting them until there is some drag when turning the drums. It usually works out well for me. Good luck

 

[cudak888]

Did you check the bearings for smoothness when the shafts were out? If so then it sounds like your on the right track. Also you can check the pinion for excessive slack, with the trans in neutral move the drive shaft back and forth.

Bearings felt nice and smooth.

Now as for pinion checking - how about in park? I could get quite a bit of clanking from the pinion and shaft just by spinning one of the wheels and reversing its direction quickly. Felt like slack to me.

-Kurt

 

[RT K_line]

I've never tried it that way. But you should have less than 10 minutes of rotation. Meaning think of the shaft as a clock, turn the shaft one way, Mark the bottom of the shaft and turn the opposite direction, check the mark. Usually excessive play here is a companies by a winning noise on acceleration or deceleration.

 

[miller]

Axle end play...I ran into this one time...inside the carrier, where the axle ends meet, is a steel 'button'. That particular time, it was laying down on the job. Flat surfaces should be, for the axle ends to meet. Mine had rotated, showing the curved surface...simply had to reach in there, and move it around.

Don't know where your at on it, but if driveshaft and axles are pulled, I'd look hard at your third member. Gotta wonder if something came loose. Feel for both pinion end play, in and out, and back and forth, via the yoke. Member should rotate pretty freely, the same, full circle. If not...I'd pull it, and find out why.

 

[cudak888]

I've never tried it that way. But you should have less than 10 minutes of rotation. Meaning think of the shaft as a clock, turn the shaft one way, Mark the bottom of the shaft and turn the opposite direction, check the mark. Usually excessive play here is a companies by a winning noise on acceleration or deceleration.

I'll do this as soon as I sort out the axles.

Axle end play...I ran into this one time...inside the carrier, where the axle ends meet, is a steel 'button'. That particular time, it was laying down on the job. Flat surfaces should be, for the axle ends to meet. Mine had rotated, showing the curved surface...simply had to reach in there, and move it around.

Don't know where your at on it, but if driveshaft and axles are pulled, I'd look hard at your third member. Gotta wonder if something came loose. Feel for both pinion end play, in and out, and back and forth, via the yoke. Member should rotate pretty freely, the same, full circle. If not...I'd pull it, and find out why.

Tell me, how does the axle physically interact with that button in the center section? Doing a few Google searches, and though people refer to it, I can't find a picture.

When fiddling about with the axles, I could see the butt end of the other shaft clearly through the third member. Should I be seeing something else?

-Kurt

 

[miller]

Tell me, how does the axle physically interact with that button in the center section?

Sure. First thing is, what bearings are you using? I've never used 'green' bearings, but understand the button must be removed! If your using Timkin bearings, normal, that button IS used. Stock setup.
Button is a hard steel 'disc', around 1/2 to 5/8" thick, with surfaced flats. End of each axle fit against the flats of the disc, or button, so the axle ends don't ride against themselves. Simply a surface the axle ends ride against, and that's what you set the end play against.
Hate to say this...but from that photo, the end of that axle looks BAD. If your using green bearings, suppose it might not matter. That end of both axles should be flat, except the centering drill hole.
IF the third member is in the housing, looking inside (as shown), you would see the button, from each side.

 

[miller]

Checked...button (my term), is called a thrust block...if that helps.

 

[cudak888]

Sure. First thing is, what bearings are you using? I've never used 'green' bearings, but understand the button must be removed! If your using Timkin bearings, normal, that button IS used. Stock setup.
Button is a hard steel 'disc', around 1/2 to 5/8" thick, with surfaced flats. End of each axle fit against the flats of the disc, or button, so the axle ends don't ride against themselves. Simply a surface the axle ends ride against, and that's what you set the end play against.
Hate to say this...but from that photo, the end of that axle looks BAD. If your using green bearings, suppose it might not matter. That end of both axles should be flat, except the centering drill hole.
IF the third member is in the housing, looking inside (as shown), you would see the button, from each side.

Running stock Timkin needles.

From your description then, I shouldn't be able to see the axle ends if the buttons are still in place, right?

FYI - if the axle end looks warped, that's gear oil causing visual distortion. They're both nice and flat at each end with exception to the center divot.

-Kurt

 

[Daves69]

Some old gear info here................
http://www.mymopar.com/index.php?pid=453

 

[coloradodave]

That's correct. Without the thrust button in place there is nothing for the right axle to butt up against so you can't properly adjust the end play of +-.008-.010". The buttons I've experienced were 2 piece with a roll pin holding them in place. Kind of like a mini 'bar-bell'.

 

[miller]

From your description then, I shouldn't be able to see the axle ends if the buttons are still in place, right?

That's correct. It's possible someone pulled it, to run green bearings (why it's not in place), or, it's out of place.

FYI - if the axle end looks warped, that's gear oil causing visual distortion. They're both nice and flat at each end with exception to the center divot.

Ahh, okay. What I get for closing one eye!
Still, just going by the sound (pun) of things, curious if you've done those basic backlash checks on the gears?
At the yoke, in and out should be minimal, basicly a very small amount. Side to side ring and pinion should be only slight. You should be able to feel some free backlash, but not that much, so there's no binding on the gears. And, like mentioned before, the free rotation thing. If it binds anywhere through the full circle...problem.
Just common sense checks, to look for the obvious.

 

[cudak888]

Hmm. This is a bit interesting, because from the photos I've seen since making this post and reading your replies, I'm not quite sure how the hell the pinion gears are being supported in the case to begin with - as you can see, I have a pretty unobstructed view of the butt end of either axle from the housing ends.

I'll do the backlash checks this weekend (should the checks be done with the axles installed or removed?), but I have a feeling I'm going to be dumping the center section out one way or another.

-Kurt

 

[oldbee]

You have the side gears that the axle slides in to & pinion gears that balance those out & thrust washers behind each gear. Maybe some/all of any of the above are worn out. Those 4 years all mesh with each other to balance out each other with a cross-shaft between the pinion gears to hold everything together.

 

[cudak888]

You have the side gears that the axle slides in to & pinion gears that balance those out & thrust washers behind each gear. Maybe some/all of any of the above are worn out. Those 4 years all mesh with each other to balance out each other with a cross-shaft between the pinion gears to hold everything together.

EDIT: Scratch everything I said below. Isn't that the thrust button that I'm looking at, not the other axle shaft?

And that's my worry. The more I learn what that diff is supposed to look like, the more I worry about what I see - the butt end of each axle, with no visual obstruction:

Which leads me to ask: Where on earth is the pinion gear shaft? Floating in there loose with only the side gears keeping them barely in place?

-Kurt

 

[coloradodave]

Remove both axles. If you can see from one side out the other, the centering block is missing. If you can't, the block is in place. That picture sure looks like the block with a roll pin in the center (like my 'barbell'description above).

 

[miller]

Correct me if I'm wrong...there are two different 8 3/4" carriers, point is you need to know which one your looking at, first. Think the numbers are cast on the driver's side of the housing. Do you have a service manual??? It would show the parts break-down for both, so you can get a better idea what your looking at.

Still wondering if 'something' is either wore-out, or come loose, in the carrier. Checking backlash (axles out) might tell if something is amiss...might not, too. Sorry if it sound confusing, but all the parts that make one of those guys work right, is not a simple deal.
But, as you said, something in there isn't right...just need to find out what.

 

[Daves69]

EDIT: Scratch everything I said below. Isn't that the thrust button that I'm looking at, not the other axle shaft?

And that's my worry. The more I learn what that diff is supposed to look like, the more I worry about what I see - the butt end of each axle, with no visual obstruction:

Which leads me to ask: Where on earth is the pinion gear shaft? Floating in there loose with only the side gears keeping them barely in place?

-Kurt

Measure the depth to the axle flange. See if it matches the axle.
A 489 case with sure grip looks the similar.............

 

[cudak888]

Correct me if I'm wrong...there are two different 8 3/4" carriers, point is you need to know which one your looking at, first. Think the numbers are cast on the driver's side of the housing. Do you have a service manual??? It would show the parts break-down for both, so you can get a better idea what your looking at.

Still wondering if 'something' is either wore-out, or come loose, in the carrier. Checking backlash (axles out) might tell if something is amiss...might not, too. Sorry if it sound confusing, but all the parts that make one of those guys work right, is not a simple deal.
But, as you said, something in there isn't right...just need to find out what.

Almost certain I have a bottom-end 741. Will have more to report on this weekend when I pull the axles again.

Measure the depth to the axle flange. See if it matches the axle.
A 489 case with sure grip looks the similar.............

Probably will. Can't imagine the thing working at all without this piece.

-Kurt

 

[miller]

Probably grabbing at straws...but, while you have the axles out...make sure both are the same length for a B-body, and for straightness.
Going to be interesting to hear what you find. Good luck on it!