4wd clunks hard, does not immediately engage when selected

[6716]

Let me start with transfer case fluid has 10k miles on it, and was serviced about 50k miles before the previous service, so I don't think it is fluid or service interval.

The issue started last year when I was driving with 4Hi on through some snowy bits, and then turned sort of sharply onto some dry pavement to park (so I wasn't moving very fast). There was a loud clunk but I didn't have other drivability issues but I didn't feel like 4wd was engaging after that. Like in other situations I would select 4Hi but didn't gain traction and just spun the one back wheel.

I didn't deal with it because I had other things but now interestingly it has actually seemed to work on occasion.

Tonight I was backing uphill and spinning the rear wheel, so I selected 4Hi and it didn't immediately engage, but then there was a loud clunk seemingly under the driver's seat and then I had 4wd.

So it seems like something in the transfer case but I don't know where else to start.

Thoughts?

Thanks

 

[Mooseman]

Even though you describe the noise as under your seat, I'm thinking the disconnect as I consider it the weakest link. Maybe it wasn't quite meshed together and when you applied some gas and slip, the gears got together all of a sudden.

Before I'd suspect the transfer case, I would certainly give the disconnect the stink eye.

 

[6716]

Well shoot. I wish I had brought it up a couple of months ago and taken care of it while I was replacing the lower control arm brackets. Oh, well. Maybe I will dream up something else to get done on the front end at the same time. I was kind of hoping after new hubs, calipers, LCAs, and brackets that I was done up front for a minute. Maybe I will re-re-do the UCAs, they have 60k miles on them.

It looks like people have struggled to remove the thing based on threads I read.

It definitely seemed like something broke on that one day when I turned onto dry pavement from the snowy road, it was definitely a noise from up front. What part of the disconnect would that have been do you suppose?

 

[Mooseman]

Probably the shift fork or the dog gear that locks the input and output gears together.

It might or not be stuck to the oil pan. Start spraying penetrating oil on it now. There is a way to get it off without breaking it in the pan by spinning it in the hole, not prying on it. Maybe heat around the pan hole might help.

 

[NJTB]

This happened to me, the shift fork in the disconnect broke. Bought a new one and rebuilt it.

 

[6716]

well, hold up.

The splined disconnect only affects the right side axle, right? The Front Drive Axle Clutch Sleeve connects the splined bit of the right outer axle to the splined bit of the inner axle.

So if I have 4wd selected and the transfer case is engaged, isn't the left front wheel being powered? Or does it have to do with the front diff being open, (is that why no power would be going to the left front if the right front were not engaged) ... like with a non-locking rear diff, if there's no traction one wheel will spin and the other is stationary? Like if the fork is broken in the disconnect, it's like the right side is "spinning" ... sort of theoretically?

Reading the manual, looking at the diagram, trying to figure it out ... it makes more sense than it did, but not total sense yet.

 

[Mooseman]

So if I have 4wd selected and the transfer case is engaged, isn't the left front wheel being powered? Or does it have to do with the front diff being open, (is that why no power would be going to the left front if the right front were not engaged) ... like with a non-locking rear diff, if there's no traction one wheel will spin and the other is stationary? Like if the fork is broken in the disconnect, it's like the right side is "spinning" ... sort of theoretically?

That is correct. You won't get anything to the left front wheel.

 

[6716]

So having 4wd selected, with the open diff in back, is really 2wd, one front and one rear, though those two wheels are essentially locked to each other?

But with a G80 locker, it's 3wd, which is essentially saying "I hope one of these 3 wheels gets some bite here."

 

[6716]

Ok. The disconnect will simply not come free of the oil pan. We took the disconnect apart to get the half shaft out, with the back half of the disconnect still on the oil pan, and put a ratchet strap around the front part of the disconnect and bolted the cover back on and put a bunch of tension on it.

I've been hitting with pb blaster. And a hammer. Little bit of prying but I don't want to damage the oil pan.

Not sure what else to do.

 

[6716]

Also the pin on the fork is not broken, and the actuator actuates.

 

[flyboy2610]

The disconnect is corroded to the oil pan. Try using a hammer and tapping on the side of the disconnect, not front to back but up and down. Trying to remove the disconnect before breaking the corrosion bond is almost guaranteed to break it. Tap on the side of the disconnect like you're trying to rotate it towards the ground, then tap on it like you're trying to rotate it towards the hood. Once it will rotate, then start trying to get it out of the hole. Pull/pry it out just a bit, then tap it back in. Pull/pry it out a bit further, then tap it back in. Repeat the process going a bit further each time, and eventually you will get it out.
Brute force will destroy it.

 

[6716]

I'll try that thx.

 

[6716]

It spins a little but not much, back and forth a few times but no major movement

 

[6716]

It's off. Thanks for the tip!

 

[flyboy2610]

You're welcome!

 

[6716]

Do I want to replace the half shaft on this side? I haven't started the reassembly yet. Halfshaft is original but the boots are ok. Seems like the retaining clip has a lot of play in it but I am comparing it to my recollection of the retaining ring on the other half shaft when I replaced that one.

 

[flyboy2610]

I'd say it's your call on the axle. If you have any doubts about it, this the perfect time to replace it. You could always keep the original as an emergency spare.

 

[Mooseman]

Usually it gets replaced when the disco destroys it. But if its still good, I'd put it back in.

 

[6716]

I put the half shaft back in, thanks, and got everything put back together, plus as a bonus I replaced the upper ball joint on that side, it was floppy.

I think the 4wd works, or at least it worked the one time I tested it tonight. On dry pavement the steering bound up in a turn like it does with the 4wd engaged, and it clunked a little coming out of 4wd.

So thanks, Mooseman, for pointing me at the disconnect. I can't say exactly what the problem with the old one was, but the grease was old a little stiff. The roller bearings seemed to be ok, and the pin on the fork was good, and I don't know that the seals were bad.

Oh well, all's well that ends in a truck that drives down the road.

 

[6716]

So ... what if it maybe wasn't the disconnect?

Ok, so I changed the disconnect, as detailed above. Tested it real quick on some dry pavement and it seemed like it engaged just fine.

But then I didn't need 4wd until the winter. It engages, but it kinda makes a grinding noise. And I'm the kind of dumba$$ who's like "yeah that'll probably go away" but it mostly didn't. I mean, it didn't until the 4wd stopped engaging again. I got maybe 3-4 little sessions of 4wd out of it.

And then I got busy and didn't have time to think about it.

But here I am again, thinking about it.

Now, the last disconnect I took off, I also took it apart, and like I never looked at one before but I did a bunch of reading and it didn't look all destroyed like I would have expected, based on what I read.

It could be the actuator, except that kinda checked out when I had it apart. It would be weird for the new disconnect to go immediately bad but I suppose not impossible.

Could it be the half shaft on the *right side? That is still original, even though I had it out to do the disconnect. That doesn't really make any sense. But like imagine the actuator actuates and the disconnect connects and then things kinda work like they should but then stop again.

Anyway, thanks for reading.

 

[6716]

I suppose it could be the diff as well. That mofo leaks hard.

 

[Sparky]

If you can, when it stops working, keep it in that "non-working but supposed to be" state, jack it up, and see if you can figure out what isn't engaged. Is the actuator actually engaged fully, or it is partly trying then failing because it is weak? Is the diff making a funky noise when you spin stuff? etc.

 

[Mooseman]

It could also be the intermediate shaft, the one that goes from the diff to the disco.

Stripped Intermediate Shaft