77 460 w/ C6 and divorced np2 4x4.

I've had this truck for 5 years and my 4x4 operation has never been reliable. First the transfer case had issues so I rebuilt that. Then the linkage was broken so I fabricated one that works. I've replaced all ujoints and rebuilt my driveshafts. Front hubs are new Warns that click into place like they should.

I was confident that all of this would get my 4x4 working but tonight was the first time I had to test it and it failed miserably. Was stuck in the mud, shifted the transfer case into 4L, locked the hubs and..... Nothing. Still stuck.

Got it winched out and into the shop. Confirmed that the front driveshaft was engaged. Put the front up on jackstands and the hubs seem to lock.

With hubs unlocked: both wheels spin freely from the driveshaft.
With hubs locked: both wheels spin opposite from each other when spun by hand.

Put the rear up on jackstands and with tc engaged and the truck in gear, rear wheels both spin in the same direction. Passenger front spins in forward direction. Driver front doesn't spin at all.

What the hell is going on??

 

With an open differential one wheel will spin the opposite direction if you spin the other. so this is nothing.

If one front wheel spins with power and the other doesn't , assuming they're both off the ground, it sounds like your driver front hub isn't engaging properly. just because it moves the other wheel by hand doesn't mean much it takes very little to do that.

 

Any better way I can test that hub? Does it make sense that both rear wheels would be spinning the same direction? I believe my rear diff is also open.

 

Someone could have installed a limited-slip diff, or a locker at any time in it's past. So hard to say until you open it up and check.
Or, if there are two of you, you can turn one while the helper holds the other one steady. If the spinning one becomes notably harder to turn, chances are you have a limited-slip diff.

For checking the locking hubs, yours should be an open-knuckle diff with the axle u-joints visible. Correct?
If so, then you can lock a hub and try to spin the wheel while you jam a prybar or similar locking device into the u-joint area. If you can't turn the wheel in either direction with the axle locked up like that, the lockout would seem to be working. But definitely try to spin it in both directions, just in case.
Seems like that would be a relatively definitive test.

By the way.. Are you sure that this is a part-time NP205 transfer case, and not a full-time NP203 that was converted?
And speaking of unknowns (to us at least) just how did you modify/fix the shift linkage on the t-case? Are you sure that both shift rods are going into their proper detent positions when expected? It does sound as if they are, but I figured I'd check since I'm curious about the linkage.
The reason it seems to be working at the t-case is that you said that when shifted into 4WD the front shaft is engaged. Meaning you can't turn it by hand while in 4WD. Correct? If so then it seems that the t-case is working fine (thanks to your fixing it before) but something is going on up front.

Obviously not sure here either. Just spitballing for the moment until some sort of Ford light bulb moment happens with someone!
Good luck.

Paul

 

Thanks, Paul! Yes, I'm sure it's a part time np205 and I have confirmed the shift linkage is working properly. I always had troubles with it before. Usually had to crawl under the truck with a hammer and/or sure iron to manually shift it. It's a very farm-grade lever mounted to a bracket that pivots on a mount connected to the trans. Was hard to access the mount to figure out what was wrong but I recently pulled my tailshaft housing to replace the seal and learned that the shift-bracket had been broken. Fabbed up a new one and now (it's not always easy) I can reliably get the t-case shifted. 4L being all the way forward (shift rods all the way into the case) is easy to find.

I'm not sure exactly what my front axles look like but will try to check them out tomorrow.

The reason I don't believe I have a locker in the back is whenever I get stuck in snow or mud I only have a one-wheel-wonder under me. My bmw has a limited slip rear end and never gets stuck. How embarrassing is it that my huge truck on 37s is a disaster in the snow!?

 

It's possible something is buggered up in the rear too then. Or, as is common with older, tired and worn out limited-slips, it might still turn both wheels in the same direction when under no load (up in the air) but not have enough grip in the clutches any longer to do any good when actual torque transfer is needed.
We used to see this all the time in the factory Ford limited-slip diffs. Customers would complain about the units not working right when they got about to the 60k mile mark or so. Seemed like a consistent mileage to where they became ineffective.

Guess we won't know until you get the time to open it up and take a look-see. Maybe your open diff just happens to have enough internal friction that the unloaded wheels will spin the same direction even where no limited-slip is present.
Don't know if it's possible, but I can see that happening in my mind.

Paul

 

I've never changed the rear diff oil and it leaks a little bit so sounds like a good excuse to do that. I'll try and report back what I find.

 

Perfect timing then! Get that old junk outta there and put in some nice fresh food for the gears.
And stop that leak at the same time. Is it coming from the cover gasket (hopefully)? Dana 60 I presume?

Paul

 

Both wheels turning the same direction under power would be normal for an open axle.

i was assuming you had an open knuckle front axle but if you have the closed knuckle there could be issues in there.

 

Good catch 440. I was fixated on the "turning by hand" scenario, but he clearly stated that the engine was doing the turning.
Thanks

Paul

 

Yes. Dana 60 leaking from the gasket. I've heard good things about the lube locker gaskets so I'll try one of those.

Got it. 99pct sure it's an open knuckle but I'll verify in the AM.

 

Deleted....

 

D60 is open knuckle and rear end appears stock?





I think I have found the issue (maybe.) Both hubs seem to lock and if I get it into 4L I think it works..... But the problem is actually getting it to shift into 4L.

I can shift from 4H to 2H to N with my shifter without any issue.... And sometimes it seems like it goes into 2L. But getting into 4L is absolutely impossible without crawling under the truck and wiggling the front drive shaft while someone else works the lever. I've put a big pipe over the shifter and everything is solid, I just can't get it to engage without some help. Obviously when you're stuck you are in the mud or snow or on the boat ramp so this is less than an ideal place to be crawling around.

Any tips/ideas on how I can improve/fix this?

 

Yes on the stock "open" differential. You could have a limited-slip and still be "stock" of course, since those were optional just as were different gear ratios.
But yours is the base model at least in the rear. Since front and rear could be optioned separately with limited-slips (I believe) you can still have a different setup in the front.

Have you changed the gear lube in the transfer case lately? Maybe cleaned up the exposed part of the shift-shafts and lubricated the pivot points on the shift mechanism?
Hard to imagine that just a little lube can fix something that can't even shift with added leverage, but you never know. And it never hurts to optimize as much as possible to narrow down the issue. Could be one thing, could be a case of "stacked tolerances" fighting you.

Good luck. Sorry not more insight into the shifting thing.

Paul

 

I appreciate the words nontheless. Linkage could probably get some lube on it but the transfer case oil is pretty fresh and the shift rails are clean.

This was my first time doing a rear diff change..... People aren't kidding about the smell. My whole shop stinks now!!