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AWD Transfer Case Problem

JakePSD

Well-Known Member
Joined
March 25, 2010
Messages
402
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City, State
Ohio
Year, Model & Trim Level
2003 Mercury Mountaineer
The transfer case on my girlfriends 97 AWD V8 Mountaineer is making some God awful noise. I just put a new (junkyard) front drive shaft in the truck since it didn't have one when we bought it, and I noticed as I was tightening the bolts at the Tcase end the flange would slip and pop when I put a decent amount of torque on the wrench. I knew then something wasn't right but I proceeded to finish putting it on anyway just to see what would happen. As I pull out of my driveway, which is covered with snow, when the rear wheels begin to slip there is some loud popping/grinding sounds coming from the transfer case. Even making a turn causes it since obviously the front and rear wheels are spinning at different speeds.

What do you guys think is wrong inside it? Is the transfer case on these rebuildable? If so, is it something a good DIY mechanic can do? I've torn apart regular 4x4 tcases and they worked when I put them back together. If this isn't rebuildable, how much do they usually run and does anyone on here have one for sale?

I now realize why that son of a ***** didn't have the front d-shaft on it when he sold it. :mad:
 



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IMO, an AWD vehicle driven without the front shaft for extended periods of time will damage the Viscous Coupling inside the center differential (you call it a "transfer case" but that's incorrect technically).
Now, the shaft you put in it might be also defective - I am rebuilding now mine because of popping noises in the shaft - rear CV was very "loose" when I pull it out.
 






It's not the shaft. Like I said, when I was tightening the tcase end bolts i could clearly feel, see, and hear it slipping. Driving it makes some horrible sounds from the same slipping. I don't know if the VC unit in it is bad or what.

She's about had it with this truck.
 






If you do replace the transfer case, make sure you get the correct one.

Most 97 models have a speed sensor in the t-case output shaft.
Late 97-up moved the speed sensor to the ABS sensor in the rear diff, so they have no sensor in the transfer case.
 






I'm not sure what she wants to do at this point. She's been wanting a Fusion for a while and had thought about keeping this to drive in the winter, but with this problem she is considering just using it for trade in for the Fusion when she gets one, probably this spring. She keeps saying that its been one problem after another since we bought it because we had to replace the ball joints and tie rod ends, and had issues with the door wires being broke, which I told her is normal on a 240k mile vehicle, and those are all fixed now. The engine runs really good and the trans seems to be in good shape, we haven't had any issues out of either of those besides and intermittent check engine light which is an O2 sensor code, neither power or fuel mileage seems to have suffered. She told me earlier that I'm not gonna convince her that it's a good truck. :dunno:

She paid $1500 for it back in october, knowing it needed new lower ball joints and that the speedometer would cut out sometimes. The guy had already replaced the uppers. I looked over the truck pretty good but didn't notice the missing front shaft. But in my defense, really who the hell is even gonna think to look to make sure it's there? It's an AWD vehicle, you expect that to be there. When I was replacing the ball joints and tie rods is when I noticed the missing shaft. Called the guy and he claimed he didn't know it was missing. Knowing what I know now I call BS. I'm sure he knew about the problem and just took the shaft off to sell it and hope someone didn't notice, along with the missing check engine light. Yep, that's right. When I was diagnosing the intermittent cutting out of the gauge cluster I noticed that the bulb for the CEL was taken completely out. Shady son of a *****.
 






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IMO, an AWD vehicle driven without the front shaft for extended periods of time will damage the Viscous Coupling inside the center differential (you call it a "transfer case" but that's incorrect technically).
Now, the shaft you put in it might be also defective - I am rebuilding now mine because of popping noises in the shaft - rear CV was very "loose" when I pull it out.

I've been in a debate about this with some people on here before. In my opinion, it wouldn't damage anything. The front output would just free spin at whatever speed the rear is spinning. There is no resistance other than air, which would be miniscule compared to even that of tires having 1/32" difference in tread. I could be wrong, but based on my understanding of these trucks (which is limited, especially the transfer case/center differential) and the laws of physics, I don't think I am.
 






If one were to drive with only the front shaft and no rear, I could see that tearing up the VC in very short order, but with no front shaft its still a direct drive to the rear wheels, leaving the front to free spin.
 






No, it's NOT. This is NOT a classical TC (with clutches between rear and front shaft), this is a true differential.
VC is locking the rear-front axles together, transmitting the 100% or torque when front shaft is missing. If the VC wasn't there to transmit the locking torque, the different axles would spin like a FWD diff when one tire is on ice. That means the tire on ice (like the missing front shaft) will spin very fast, and the other will not move at all. That's what a open diff does.

Read the document that I linked, somebody posted a similar GM document (the GM had center diff with VC for their trucks too).
 






Her truck hasn't had a front shaft in it since we got it. It drives perfectly fine without the front shaft. It feels and drives exactly like a 2wd would be. The diagrams and pictures I've seen of the 4404 look like a direct link from the transmission to the rear wheels, with the front having the viscous clutch. I never saw a clutch between the input and the rear output.
 






Well, you are wrong. Your VC is solidified by now, that's why was driving in 2WD and not anymore in AWD. There is no direct connection between input shaft and rear shaft.
I posted the above link to the BW4404 (that was used in GM too).
www.rsgear.com/tsguides/Borg-Warner-4472-4404F.pdf‎ I suppose they don't know what they are talking?
Also another user posted here some similar info from technical bulletin.
To prevent damage to the viscous coupling, DO NOT:
Tow with only two wheels down
Drive without one propshaft
Drive with a "donut" spare tire for an extended period of time
Again, those don't have a clue either?

You can choose to think otherwise, I'm out. Please read the links if still not convinced.
 






Ain't gotta be a dick dude. I'm still learning about these trucks. I read those links but it still seems like it would be fine without the front. Also, if there is no direct link between the input and rear output, then wouldn't there would be slippage at all times, much like an older vehicle that doesn't have a lock up torque converter? Asking to learn...

Anyway, here is the fluid I just drained out of her tcase/center diff. Eeww... There was even some streaks of lighter, almost silver colored fluid in there too. I'm guessing this is what happens when a viscous unit decides to defecate all over itself?

20140125_200905Large.jpg


20140125_200924Large.jpg


I don't see even a HINT of red in there...
 






You have no clue how a differential works but you choose to disregard what those links say?
Do you have a FWD car? In it there is no direct link either between wheels and transmission, is trough differential gears. That means when you have a wheel off the ground (removed like your front shaft), the other would NOT move. Try it on your driveway.
Also, if you raise BOTH wheels, rotating one by hand will rotate the other in reverse.
This is different from a classical Transfer Case, that has no such capability - that's why it cannot be driven on asphalt in 4x4.

That's what the VC does - when there is a difference in speeds, it will heat up and will "lock" the differential output shafts, allowing power from engine to reach the wheel that has resistance. It transforms for that short period of time a differential in a regular transfer case.
But is not made to drive like that forever, only for short periods of time. Keep it heated for a few miles and it will give up.
 






I have a clue how a differential works. What we are talking about it TOTALLY different than a typical differential. By direct link I meant a solid mechanical coupling, like a gear. So in my previous post's definition of direct link, on a FWD car, such as the Escort that I have sitting in my driveway, yes, there is a direct link. With these center differentials, there is a viscous coupling to the front wheels, no mechanical link.

Edit: The reason you "can't" drive in 4x4 on dry pavement is because of binding caused by the wheels spinning at different speeds due to turning or slight differences in tire sizes due to wear. You can drive in 4x4 on dry pavement, but I wouldn't recommend in for long periods of time as it will cause extra wear and heat in the transfer case.

I did do a little experiment, as I was backing the truck off the ramps I put it in park near the top. It slowly creeped its way to the concrete. So I now realize that there is no solid link. So what does that mean, that the front output was actually spinning the opposite way when I did that?
 
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Yes. It was doing what your Escort would do with one wheel on ice. The VC needs normally some "spinning" time to heat up and lock the two output shafts. Mine takes a couple of seconds.
There are some FWD cars that have a limited slip (VC) inside too, that works exactly like your central differential.
The rear diff on your truck can be LS too - if you have that one (usually it came with AWD).

The fact that is still creeping in park is an indication of being a true open differential. VC won't work at that low speed of rotation (to lock the axles). And based on color of your fluid... you might not have a VC anymore.
 






On my mountaineer it locks up almost instantly. Almost makes me wonder if the VC in it is more locked than anything. I know it makes a bit of a low pitched whine when I make sharp turns. Oh well, screw it, it still works.

On hers, when I did my little ramp experiment, it creeped down the ramps real slow. This was with no front shaft. I took it off after the horrible grinding popping sounds that was coming from the CD after I put it on.
 






The fact that it creeps makes me think the VC still works. A fused VC would essentially make the transfer case a full-time 4wd box with no way to disconnect it.

While I agree in theory with Sonic, I had my own rig running without a front driveshaft for an indefinite amount of time (at least 6 months, previous owner had it removed). Finally reinstalled the shaft and it seems to work just fine.
 






I stopped reading when it got stupid, buy I have a 2000 AWD tcase that is in mint condition, doesn't have the sensor in it though
 



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The fact that it creeps makes me think the VC still works. A fused VC would essentially make the transfer case a full-time 4wd box with no way to disconnect it.

While I agree in theory with Sonic, I had my own rig running without a front driveshaft for an indefinite amount of time (at least 6 months, previous owner had it removed). Finally reinstalled the shaft and it seems to work just fine.

That thought had occurred to me as well, but I wonder what the popping is. I guess the chain could be slipping or something. Either way, looking at the color of the fluid makes me think the VC unit is junk. That or it was just never changed in the 240k miles that are on the truck.

I stopped reading when it got stupid, buy I have a 2000 AWD tcase that is in mint condition, doesn't have the sensor in it though

Exactly which point did it get stupid? Haha. Unfortunately that tcase probably won't help me will it?
 






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