Rear wheels don't move but draveshaft does - uh oh

[M@2s]

Hey folks,

got a new one after running some diagnostics and coming up with what I thought was the issue.

Something broke and then made a metalic tink sound every time my rear driveshaft turned. This is as I was a block from home, so I put her in front drive and made it back. initially I thought I was dealing with a transfer case output shaft, so O bought a bulkier one and went to replace the old one, only to find that as I was taking nuts and bolts apart from the front joint of the driveshaft, I could turn the driveshaft and not have my rear wheels move. I then decided that pulling the entire rear out to clean it up and figure out what was going on.

Well, after taking out the axles and removing the third member, I don't see anything obvious and the everything turns real smooth and has all teeth in tact with no apparent wear. I've heard that when there is no load, a broken pinion nut and a few other things can be culprits but now I have the third member out and it's tough to test much.

Any suggestions?

Dealing with 9" rear, Currie housing, 31 spline axles, 11" drums, large bearings and a detroit locker, on 4.56 gearing

Thanks ahead of time
images at:
https://www.homeloanbasecamp.com/bronco

https://static.wixstatic.com/media/.../w_750,h_563,al_c,lg_1,q_85/3rd member 2.webp

https://static.wixstatic.com/media/...1/fill/w_750,h_563,al_c,lg_1,q_85/axle 1.webp

https://static.wixstatic.com/media/.../w_750,h_563,al_c,lg_1,q_85/pinion input.webp

https://static.wixstatic.com/media/...c,q_80,usm_0.66_1.00_0.01/rear diff back.webp

 

[WILDHORSES]

This is not making sense. Looks like you have a good ring and pinion. Peak inside the axle bore of that Detroit. Something would have to be really torn up inside that unit for it not to move at all when you turn the drive shaft.

Jim

 

[.94 OR]

I would drop the pinion carrier out and see if there is anything lurking in there.

 

[M@2s]

If I drop the pinion carrier, is there anything I should know ahead of time for keeping alignments or anything? I'd seen a lot about third members but very few videos on the pinion carrier removal. I have freed the bolts, is this all I have to do besides breaking the gasket seal free?

 

[Timstrk]

Can you hold the ring gear and turn the pinion shaft by itself. Broken pinion shaft binding just enough to make everything seem good?

 

[Nothing Special]

Can you try sticking the axle shafts into the diff to see if they can turn without the ring gear turning (to look at whether the Detroit is broken)? If you stick one axle in one side and try to turn it you won't be able to unlock the Detroit so the ring gear ought to turn. Try that on both sides.

 

[rmk57]

There's not a lot of moving parts in locker. Mark your caps with a center punch, take it apart and it should be pretty clear as to what the carnage is.

 

[.94 OR]

The pinion carrier has the obvious 5 bolts on the cover, likely some shims that are obvious and then an O-ring around the carrier. Other than that it will come out pretty easy. There shouldn't need to be any indexing here as the pinion teeth and the ring gear mesh up differently on each turn of the driveshaft.

 

[Timmy390]

My limited slip did what your's is doing right after my 351W upgrade.........

What I found when I got inside......Hope your's is not like mine.....

Tim

 

[Jfryjfry]

If you turned the rear driveshaft and neither wheel turned before you did any work, then the problem is between the parts that turn and the parts that don’t. So before you start taking things apart (too late) check everything to make sure you know exactly where the problem is(even if you don’t know what exactly the problem is.

 

[blubuckaroo]

Broken spider gears?

 

[Nothing Special]

Broken spider gears?

No spider gears in a Detroit

 

[Hazegray]

My vote is broken pinion gear

 

[Glass Pony]

OP, I had the exact same symptoms that you described when I busted all the ring gear bolts. But it was real obvious when I pulled the third member.

 

[Justafordguy]

It's going to be a broken pinion shaft or a busted locker, probably the locker I'd Just pull it apart.

 

[langester]

My limited slip did what your's is doing right after my 351W upgrade.........

What I found when I got inside......Hope your's is not like mine.....

Tim

I had one of these units do the same thing. Not sure if the lockers break there as well or not. Good luck with it!

 

[Yeller]

Had 3 things cause that in the past for me.
1- broken pinion shaft, however they normally break at the end of the splines spitting out the driveshaft but have seen them between the bearings
2- debris from other failure stuck in locker holding it open so it can’t engage, this usually is obvious, broken ring gear, axles ect.
3- broken locker but normally includes a broken axle/axles.

The first requires an new ring and pinion. 2 and 3 require disassembly of the locker cleaning, inspecting and reassembly. Even if broken I’ve always had them function when reassembled, they just may no longer unlock when turning.

Tip for those that break one on a trip from a broken axle and you have a replacement axle, disassemble the locker. Clean all the parts, removing all debris, reassemble and go wheeling you’ll probably have a spool but you’ll be living life and enjoying yourself again.

 

[Nothing Special]

It's going to be a broken pinion shaft or a busted locker, probably the locker I'd Just pull it apart.

I'm thinking probably the locker as well. But I'd figure out which before I took it apart. Try to turn the driveshaft yoke while holding the ring gear still. And try to turn each axle shaft while holding the ring gear still. Whichever one moves is the one that's broken.

 

[Justafordguy]

I'm thinking probably the locker as well. But I'd figure out which before I took it apart. Try to turn the driveshaft yoke while holding the ring gear still. And try to turn each axle shaft while holding the ring gear still. Whichever one moves is the one that's broken.

Yep, good plan.

 

[M@2s]

Update
I took the pinion carrier out and fount nothing obvious. The two shims may have taken a little abuse while I was working the pinion out. It didn’t just slide out but rather needed me to work the gap all the way around for a while. I’d assume that I’ll need fresh shims to keep this all from leaking in the future. Next venture is to attempt to put some of it back together and try turning one axle at a time to test the detroit. I guess I’d rather test than continue to dismantle. I’m starting to think I was crazy.. but the locker being bad might explain a lot.

Let you guys know soon. Thanks folks!