A 4wd operational question no one has been able to answer.

[clickscrazy]

05 TB LT 4wd G80

No one has been able to explain this 4wd operation experience:

4wd works great off-road (No bad sounds, no blinking links, no service lights). Sink the rears in sand, Put it in 4wd low, it pulls right out.

When the truck is on a lift (all 4 wheels off the ground), the front wheels will not spin under power (the backs will).

What you DO get is a whirling/grinding sound. Like a clutch is slipping. Everything I have researched says at least 1 wheel should spin.

I am REALLY curious as to why this happens, and no shop or forum poster has been able to tell me if this is by design, or just some weird issue.

[Trail X]

There's a misconception that when something goes bad, it results in 3WD... there's simply no such thing.

Often when a truck is on a lift, the CV shaft angle into the disconnect gets even worse due to the drooping suspension. As a result the alignment between the disconnect gears can get thrown off, especially if there is internal wear. I'd suspect the disconnect has some bad bearings at least, and possibly needs to be rebuilt - hard to tell without breaking it open.

To be sure, have you worked through the flowchart? What are your results? Explain your steps and observations.

http://www.offroadtb.com/articles/tech- ... wd-system/

[clickscrazy]

The lift/level kit is being put in today. I will run some tests when I get it back. As I go through and inspect the job and update this thread.

I was leaning towards the front disconnect as well, but all the symptoms of it being bad did not match. (Noises, staying engaged, etc.)

Questions:
1. When you say "internal wear", are you referring to the disconnect?
2. Could it also be wear on the CV axle itself, so that its not grabbing?
3. If everything tests good, should I even care?

[Trail X]

The fact that you were not lifted when you experienced this basically confirms my suspicions. A non-lifted truck has a straight CV axle line into the tripod joint. Basically nothing there to throw off the internal disconnect gear alignment. I bet the disconnect will not work well after your lift because the lift puts an angle into the tripod joint, similar to when your suspension droops on a garage lift.

1. Yes, the internal wear I'm referring to would be in the disconnect. Normally the outer two bearings and seal are damaged at a minimum.
2. Doubtful. The only thing that kills a CV shaft is lack of grease or ingestion of water in the joints - or overload at a high steering angle.
3. Refer to my statement above. You may have issues after the lift. If you don't, then I'd still expect it to be intermittent operation, and will probably not work when you need it most.

[clickscrazy]

Just a quick update here:
The lift was put in today. I tested 4wd on road, it seemed to work.

The mechanic said he believes the CV's are simply disconnected at that angle due to a bad design.

But it still does not seem right to me.

1. Based on previous input, it seems the front disconnect could use replacing. Is that what I am hearing?
2. If I have one front wheel in the air and the other with ground contact, will the one with ground contact still spin (with this issue)?

[clickscrazy]

Based on the test above, its the 4WD Disconnect.

With both wheels raised, the driver wheel will not rotate if rotating the passenger side.

With that said, I have a few questions:
1. Based on research, this seems to be an improved 4wd disconnect: http://www.ebay.com/itm/161509948512 Is this still true?
2. I figure I might as well replace the CV. I believe it is original with 151K. Can I replace JUST the passenger side CV with a Cardone or Detroit?

Thanks for all the help.

[Trail X]

CVs don't disconnect at a certain angle unless they are broken.

If you're going to buy a disconnect, it is recommended to upgrade to an AWD disconnect.

[clickscrazy]

Just did an actual test of the 4WD off road with the lift.

....and Trail X was right.

Front wheels do not engage at all. Nothing.

You can hear everything do what its supposed to, the front wheels simply wont spin under power.

The Lift made the real problem clear.

I can tell the transfer case is engaged and the diff (since in 4 lo, the gearing change can be felt), just no front wheel movement at all.

[clickscrazy]

I have ordered:
Front Disconnect: http://www.ebay.com/itm/161509948512
CV Axel (Cardone from Amazon)

A1 Auto has a great how to video. I am sure it will still be a pain, but I will post a new thread on how it went.

[Trail X]

Too bad, you should have gotten the AWD one, gotten a more reliable system, and saved some money.
http://r.ebay.com/woS4lN

[mason10198]

Trail X is right. If you can get a refund on that, just send it right back without opening the box. Buy the AWD unit from them instead. There are virtually no ill effects from the AWD disconnect mod, just a stronger system with less failure and breaking points than the mechanical 4WD disconnect.

If you swap in the AWD disconnect, just take the black electric actuator off of the old 4WD disconnect and zip tie it to the truck somewhere, leaving it plugged in. That will keep your 4WD service light on the dash from coming on.

Sent from my XT1650 using Tapatalk

[clickscrazy]

I did call that guy before I ordered. He told me I had to get the one I got.

I guess I need to research this mod a bit.

[KingBird]

Yeah, a lot of folks think that awd parts are specific to the awds.

They are very wrong.

That being said, the AWD sleeve CAN fail, but it will only happen after 120k hard miles and even then, a new sleeve, intermediate shaft, and a few hours are all you need to be functional again.

Nothing a little money and a "can do" attitude can't fix.

[clickscrazy]

I'll just stick with the normal disconnect. The factory one has lasted 150k (though that is pre-lift).

If what is said on this ebay listing is true, this is an "improved" version.

We will see.

Plus, won't the AWD version keep the diff spinning all the time? Using more fuel?

[TBYODA]

I'll just stick with the normal disconnect. The factory one has lasted 150k (though that is pre-lift).

If what is said on this ebay listing is true, this is an "improved" version.

We will see.

Plus, won't the AWD version keep the diff spinning all the time? Using more fuel?

You are correct the diff is moving all the time and the loss in mpg is less than 1 mpg if that. Btw to keep the disconnect working at peak performance service it with new grease every 2-3 years, fully clean and regrease it. Also when removing the disconnect from the oil pan, tap the housing from underneath a little on each side to create a rotational force to break it free as your applying a little outward force. Clean up the crud in the pan and apply liberal amount of anti seize before you install the new one.
If you try and just pry off you could break of the disconnect housing in the oil pan as many have done.

[clickscrazy]

Thank you for the tips! Based on the photo, the disconnect seems to come pre-greased.

I was planning on greasing the splines on the new CV and intermediate shaft.

I don't understand when you say to clean the crud in the pan though. Once the disconnect is removed, I won't be able to get in the pan through the small hole with the intermediate shaft.

[larryk]

"Plus, won't the AWD version keep the diff spinning all the time? Using more fuel?"

There is a common fallacy that the diff isnt spinning with the part time disconnect vs the AWD version. Due to the design....if the drivers wheel is spinning, then the diff (not the case, but parts within) is spinning as well. Since there is no disconnect on the drivers side, movement of that wheel WILL rotate the side gear in the differential at the same speed. Since the gears are meshed in the diff, the other gears will also rotate, with the OTHER side gear rotating at the same speed, but in the OPPOSITE direction. This side gear will also rotate the intermediate shaft, and the side gear in the disconnect. The OTHER gear in the disconnect will be rotating with the passenger side tire in the same direction as vehicle direction. SOOOO...the two gears in the disconnect will roating at the same speed, but in opposite directions. (This is why I would never switch to 4x4 while the vehicle is moving, although it is allegedly good to do so under some certain speed). The only thing the disconnect prevents from rotating is the differntial case itself (with the ring gear) and therefore the pinion gear/front driveshaft/transfer case front output. That's it.

If you convet to the AWD sleeve, since this locks both side of the passenger side axle/intermediae shaft together, it forces rotation of the differential case and all of the parts noted above. No load on them, as the transfer case will be transmitting power only in 4x4, but they will be rotating with the resulting inertia/wear points.

[clickscrazy]

Makes sense. Thank you for that explanation.

[KingBird]

The disconnect sits in a little "shelf" clearanced into the oil pan.

In theory, this area is not sealed off nor watertight. Neither is the area behind the diff on the other side.

This means that water COULD pass from one side of the engine, through the hole in the pan the intermediate shaft passes through, to the other side and out.

The clearances are so small however, that oftentimes dirt and crud gets back there and gathers.

This has a way of "sealing" the disconnect to the pan, even with the bolts removed, many have had to destroy the disconnect and actually drill out the shoulders to get the old disconnect out.

That's why it's recommended that you clean that area as often as possible (when the disconnect is out) to keep that from happening with the new one.

[clickscrazy]

I tore into it today. I got the disconnect out.

The story continues here (I thought it was better to post this in the general board): viewtopic.php?f=32&t=6809

But basically, I opened up the disconnect, and didn't see any issue...