My 8 3/4 Rear End Tear-Down and Exploration!

[jenkins71]

Sup DUDES. So, tonight I got a hair under my *** and decided to take apart my rear end on my 71 Charger. Been working on this car for a bout a year, rebuilt the engine and trans this winter. The previous owner had it as his drag racing toy, with street use, and it had been sitting for a while before i got to it.

Little backstory. A few weeks ago I took this video of the pinion rotational play, and put it up here for you guys to see. I started a thread about it, and most guys watched it and said "bad bearings" or something.
(Here's a link to that thread: http://www.forbbodiesonly.com/mopar...-some-play-in-the-pinion-is-this-normal-VIDEO)

And here is that video again:

https://www.youtube.com/watch?v=Sqd12dNSFAs

As you can see, the pinion can be rotated a good amount before the wheels start to turn.

So, tonight I jacked it up and went about yanking the axles.



The first thing that I discovered was that the previous owner had installed green bearings. Now, I've always heard that green bearings were a no-no for the street due to a lack of side-load capabilities. Furthermore, I had already went online and bought a set of new tapered Timken bearings, and accompanying seals, assuming I would go ahead and replace the bearings and seals while I was in there. So, I was kind of disappointed to see the green bearing set up. I also noted that on the passenger side, the seals were badly leaking diff oil into the brakes. Would it be easy to switch back to tapered bearings? Would it be worth it?

Anyway. With the axles out, pulling the center section was a cinch.



Soon I had my center section on the bench. It is a 741 section, with 3.91 gears. I was pleasantly surprised to see that I had the rebuildable style sure-grip! The other surprise came when I once again rotated the pinion to check the free play in the unit. It had close to none!

https://www.youtube.com/watch?v=3vUzRRa1rDk

And the gears looked to have little wear, nothing abnormal looking there. SO! Where did that free-play in my first video come from? What do I need to do to correct things? What can people tell me about green bearings?

I should add. I was able to drive it a few blocks last week with the axle all together. The thing chirps and shudders in the rear like no other when turning corners. It also makes a lot of noise just leaving a stand-still.

Thanks guys!

 

[747mopar]

Green bearing are just regular ball bearings and have worked fine in the Ford 9" and many other rearends for years but tapered bearing are far superior. The advantage of the green bearing is it allows for quick gear changes by eliminating the need to adjust endplay which is why drag racers like them. Honestly though it only takes me 15 minutes to set endplay (very straight forward).

- - - Updated - - -

Check the pinion and carrier bearings for endplay using a dial indicator while prying back and forth (you just pry back and forth and get an idea if you don't have an indicator). If they seem tight then check your carrier bearing adjusters to see if one could have backed off (should have retainers). If all looks good it could be whoever had their fingers in it last just didn't know what they were doing.

 

[jenkins71]

Thanks for the advice.

One thing confuses me. Why is there so much play while the wheels are are on the ground and the center section attached to the axles, but near zero play with the center section on the bench?

Remember, this is rotational play. Rotation of the pinion Vs rotation of the wheels/ ring gear.

 

[super-bee_ski]

Great graphics!
Good points

I'm like you, I am convinced the tapered Timken bearings are best for street usage.

 

[jenkins71]

I was starting to think maybe the problem was in the differential, the sure grip unit.... Any ideas? I guess the play would be between ring gear rotation, and rotation of the axles/wheels.

 

[747mopar]

Hmmm, how is the pig being supported when your checking it now? Try turning the carrier on it's side with the ring gear down, pry the pinion forward and the ring gear away from the pinion gear to create the maximum amount of play and check again. If it's still tight then dig in, I'll be interested to see what you find.

 

[miller]

What kinda shape are your axle splines in? And the splines in the gear box?
I'd also look hard at the suregrip unit...could be wore out, or assembled wrong.

 

[RJRENTON]

Gentlemen,
The original Timken bearing set up is far superior, owing to the fact that a tapered roller bearing has both radial load and AXIAL load capabilities. Axial load is the in/out load imposed by cornering forces plus thermal expansion of the axels. The "green" style bearing if it is a roller bearing, not a ball bearing, has only radial load capabilities. If it is a "ball bearing" ,it has a slight amount of axial load capability plus radial load capability. The only true ball bearing that had high axial load capability is an angular contact bearing and only in the direction of the thrust face. In order to get true axial load capability in both directions is thru a duplex angular contact bearing. It is my opinion to use the original Timken bearing setup with the end play adjuster.
Questions?
Cheers,
RJRENTON

 

[jenkins71]

Gentlemen,
The original Timken bearing set up is far superior, owing to the fact that a tapered roller bearing has both radial load and AXIAL load capabilities. Axial load is the in/out load imposed by cornering forces plus thermal expansion of the axels. The "green" style bearing if it is a roller bearing, not a ball bearing, has only radial load capabilities. If it is a "ball bearing" ,it has a slight amount of axial load capability plus radial load capability. The only true ball bearing that had high axial load capability is an angular contact bearing and only in the direction of the thrust face. In order to get true axial load capability in both directions is thru a duplex angular contact bearing. It is my opinion to use the original Timken bearing setup with the end play adjuster.
Questions?
Cheers,
RJRENTON

I think we can pretty much all agree with that. Let's drop the green bearing subject...

I really just need advice as to why there is play in the rear end when the wheels are on the ground! I should have time to dig in soon.