Viscous Couplings

[Ifixyawata]

This is regarding the Mountaineer in my sig, first some back story:

We purchased this truck around a year ago. I'd done a TON of research on third-gen Exploders/Mounties/Aviators. I'd decided against any Aviators because of the abundance of Aviator-only parts, though the DOHC motor was tempting. Going through my daily searches of craigslist, etc I was well aware of the known issues with transmission failures, wheel bearings, etc. I also ran across a few things about AWD models and how, without proper tire inflation and rotation, the viscous couplings would fail in a locked mode.

Because I live in NE Ohio and vehicles of this vintage have a good chance of being rusted or on their way to rusted, I searched around NC where my in-laws live. My FIL had offered to go look over anything I found online. I ran across several turds like an '03 Explorer EB that was beaten to death, an '04 Limited Explorer AWD that was beaten worse, and lots and lots of 170k+ short-timers. Oh, and lots of 2wd models because, hey, it's NC. Finally, like a revelation this '04 Mountaineer appeared and with ONLY 113k! It was AWD and it had all the other things I required, V8, Leather, Sunroof. And also fit my wife's list of requirements: NOT red. I sent my FIL to look at this one, with high hopes and anticipation and he called me at work after he'd looked at it and reported back that all seemed well with it. I made sure to tell him to do some full-lock turns and take note if it was binding or struggling; he said it was smooth and easy going. He'd scrutinized everything else he could and told me that he would buy it if it were him, so we did. Picked it up a few weeks later.

Before I even got it home I knew it needed at least one front wheel bearing and at my first gas stop I noticed that the front upper ball joint boots were shredded. We bought 4 new tires because the ones on it were pretty old/cracked and worn a bit unevenly... as if they hadn't been rotated ever. Last fall I replaced the front wheel bearings (thanks, southern state, no-rust suspension components!) and just a couple weeks ago I replaced the front upper ball joints. All seems well still but I'm starting to think more about this viscous coupling.

Since we've had it, it's been kind of... hesitant to make tight turns in a parking lot. Having never owned an AWD vehicle I don't know if this is normal or if it's a sign that the VC is on the way out. Poking around online, one would think that if the VC is truly locked you'd have inside wheels skipping and hopping and the like. This is not the case with my Mutineer, but recently my wife tells me it's 'doing something strange' while making turns. I tried to get more information out of her but once I told her what was involved in replacing the VC, she's ready to sell the truck, deeming it a 'lemon'. I didn't get a chance to tell her that the VC, at least on some vehicles is considered a wear item and has a finite lifespan.

I saw a 3-part video on YouTube of the diagnosis and repair of a bad viscous coupling and I feel confident that I can do it. I even checked around online and found that, through their eBay store, a company called STE Couplers sells a re-manufactured coupling, x-fer case chain and seals for $495. That seemed expensive until I priced the coupling by itself at other places and came up all north of $600...

Mind you I haven't diagnosed this at all yet and I feel pretty confident that it's not a matter that needs immediate attention, hence my comments about not wheel-skipping. Also bear in mind that I haven't changed any of the fluids besides the engine oil yet... it's hard to justify $150+ worth of fluid changes (Transmission, x-fer case and diffs) when, insofar as my wife is concerned there is nothing wrong with any of those things. I think if I change any of the underside fluids it will be the transmission first.


So, what say you, BITOGers? Anyone had one of these 3rd gen Exploders/Mutineers with AWD? Anyone replaced a viscous coupling?

 

[andyd]

At least check the lube levels. Iwould change the ATF simply to baseline it. My Grand Wags had NP transfer cases with Viscous couplings and all performed well.

 

[The_Eric]

If it's in good shape and your wiff likes to drive it, then fix it. It's a single speed gearbox- can't be that hard. I know that I personally would.

 

[RF Overlord]

I know it's a different vehicle, but hear me out:

My work van, a 2001 GMC Safari AWD, developed a strange "grabbing" when doing tight turns, both in forward and reverse...felt like a posi axle without the friction modifier, only worse.

Turned out a transfer case seal had gone bad and allowed most of the fluid to leak out. The shop took the unit apart, replaced the seals and refilled it and it's been like new since, so at least I caught it in time.

 

[The_Eric]

Originally Posted By: RF Overlord
I know it's a different vehicle, but hear me out:

My work van, a 2001 GMC Safari AWD, developed a strange "grabbing" when doing tight turns, both in forward and reverse...felt like a posi axle without the friction modifier, only worse.

Turned out a transfer case seal had gone bad and allowed most of the fluid to leak out. The shop took the unit apart, replaced the seals and refilled it and it's been like new since, so at least I caught it in time.


In this case the coupler is a sealed unit and is not affected by t-case fluids or lack of.

 

[Ifixyawata]

I only stated that she was ready to sell it to illustrate how badly she dislikes spending money on car repairs. She likes it too much to sell and it took too long to find this one. It's partially fault because I can never prioritize my repairs correctly. For example, I, at least until now, hadn't had a clear idea of which fluids to change first so I just avoided it all together. It's hard to justify the 'why' when you're talking about changing four different fluids. Especially when I think as certain repair will net a certain result and it doesn't. I sort of lose credibility and the work that was done wasn't necessary and the money was entirely wasted. My desire for preventative maintenance covers across, to my wife, as a desire to spend money on unnecessary things.

I think the first order of business will be to check the level in the transfer case... then if that's good I may try to take out the front prop shaft.

 

[Ifixyawata]

Now I'm trying to determine which fluid this t-case takes.... some sort of Mercon or variant...

 

[The_Eric]

Yep. Any ATF type lube will due. Valvoline also has a specialty T-case lube now too- I've got some Amsoil in mine.

 

[Ifixyawata]

I'm thinking I'll just change it with some Castrol Transmax Mercon V.

 

[Ifixyawata]

I didn't even see the post above about the VC being sealed. I knew this but hoped that maybe the possibility low or old fluid could be affecting the function of the planetary gears inside. Changing the fluid is a long shot but at least it's cheap.

 

[The_Eric]

Yes- they have a silicone fluid in them. The coupler attaches the rear output to the front output via the chain and under normal driving, provides no coupling effect. When the rear output turns faster than the front, the coupler heats up the fluid inside which expands and applies clutches inside the coupler, thus giving you four wheel drive. This all happens in milliseconds.

They're good for incidental 4x4 needs but not suited for heavy duty use. It's very important to remember to keep the tires rotated and evenly worn. Also always replace all 4 at once- same brand. Stay away from anything that cause a prolonged differential in speed or load between the front and rear and the new one should live a long happy life.