To VC or not to VC

Discussion in '80-Series Tech' started by jpoole, Jan 9, 2018.

  1. jpoole

    jpoole

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    That is the question, to run a VC or not to run a VC?

    VC = Viscous Coupler

    Background:

    The VC on my '97 FZJ80 is locked up. Front drive shaft is out for now but I'll be servicing the front axle soon, reinstalling the front shaft and then plan to either pull the VC and run without it or source a used one to replace my locked up VC with. The 80 is primarily for getting into the woods and exploring with no pursuit of hard wheeling (rock crawling, mud bogging, deep fording, etc.) that can be avoided. Tires/lift will stay within an inch or two of stock. The truck has axle lockers and if I don't replace the VC I'll do the mod for locking the center diff in high range.

    My preference leans towards replacing the VC so that the truck is more sure-footed on wet, gravel, slick roads etc. I also drive a newer Subaru Outback and I like knowing I'm not going to spin a tire on a rainy day when I aggressively accelerate to merge etc. My understanding is that without a VC the 80 will essentially be 1wd (open center and axle diffs) which makes it more likely that I'll spin a tire in the slick stuff vs never noticing the slick spots. For what it's worth, driving around with only rear wheel drive I spin a tire more than I'd like. Lots of steep hills in my neighborhood in the wet is the primary reason.

    I've read from some on mud that no VC is preferable. One reason may be to avoid binding in tight turns with high traction, another may be because the VC isn't very effective in their opinion and no VC is a simplification.

    What are some of the pros and cons of VC vs. no VC? Should I source a replacement or run without?

    Thanks!
     
  2. BILT4ME

    BILT4ME

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    If you're going to that level, go part time kit with lockout hubs.
     
  3. inkpot

    inkpot SILVER Star

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    They are worthless. They tend to die with old age, and they are ALL getting old! We throw them all away.
     
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  4. gummycarbs

    gummycarbs

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    I say replace it unless you're going to go part time, in which case you'll continue to get wheel spin on slick surfaces.

    The stock AWD system is pretty awesome. Having tampered with mine, I'd say don't tamper with yours unless you have a specific reason for doing so.
     
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  5. nukegoat

    nukegoat

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    I removed mine due to peer pressure
     
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  6. scottryana

    scottryana

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    I still want someone to try and drill a drain hole drain the viscous fluid much like the fan clutch and add new. I think it could be done and might give us more adjustment on how "aggressive" the AWD is.
     
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  7. inkpot

    inkpot SILVER Star

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    I thought that would put your head gasket at risk??
     
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  8. inkpot

    inkpot SILVER Star

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    I know someone that cut a stuck one apart to check it out. I have seen it. Lots of corrosion. It was an experiment that failed. IIRC it was only in North American market for 3 years. They did not continue it in the 100 series, which could use it more than the 80s. If you really need quick traction on slippery surfaces just employ the CDL. It works great. I really cant recommend that anyone spend hundreds of $ to replace something with so little benefit and such a high risk of failure.
     
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  9. flintknapper

    flintknapper

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    What would be some of the signs/symptoms of a failing VC?
     
  10. Lumpskie

    Lumpskie

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    I'm wondering about this too. I LOVE having AWD out here with slick road surfaces a solid 4 months out of the year.
     
  11. Dork

    Dork SILVER Star

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    Sounds like you answered your own question. If you slip more than you'd like right now with the front shaft out, who cares what anyone else thinks?
     
  12. CJF

    CJF

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    Open center, no VC, AWD on an 80 series is still VERY sure footed on wet, gravel, slick roads etc.

    Remember, 91-92's came stock that way (I have two). I've NEVER thought, "gee, I sure wish I had one of those VC things..." I doubt you'll even be able to find an instance where you notice the difference.

    On the other hand, an 80 with the front DS removed, so rear drive only (like yours is now, and how one of mine currently is), does HORRIBLY on things like packed snow, etc.

    It's the AWD that makes it sure-footed, not the VC.
     
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  13. jpoole

    jpoole

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    @Dork, good question. If I had a good VC on hand I'd install it but I asked my question because not putting a VC back in saves me the time/$$ involved in sourcing one. Further, since I'd probably buy used it may save the time/$ of another replacement in the future, etc. I've also never driven an 80 with a functioning VC so wanted more information before I started trying to source a replacement.

    @CJF this is really helpful information. I didn't know if my 80 with RWD was essentially equivalent to 4WD with open center diff. Your comparison of non VC 4WD with RWD pushes me towards avoiding the hassle of replacing the VC and trying the truck in 4WD with open center diff for a while. If I'm still slipping more than I'd like I can always source/add a VC later.

    Of course, if anyone reading this thread wants to mail me the good, low-mileage VC that they pulled out I'll be glad to put it to use :)
     
  14. baldilocks

    baldilocks Battle Ground, WA GOLD Star

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    I’ve owned two 94’s and now a 93 and all had VC’s and two had closer to 300k than 200k on them and were still operating just fine. Last year I went part time on my current 80 and recently sold the VC to a Mud member because he wanted a spare. It was still working fine. How many vehicles are actually on the road 20 plus years and 280k miles??? An experiment that failed?
     
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  15. IanB

    IanB SILVER Star

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    Are you running the stock trans from a '96 FZJ80? If your trans was swapped with your 1HD-T, then you likely don't have a VC. My '93 HDJ81 doesn't have the VC from factory. I live where there's snow and ice half the year, I've never missed it. Good tires are far more important than an LSD in the center diff.
     
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  16. Lumpskie

    Lumpskie

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    @CJF @IanB

    Honestly, I'm not sure if I have a VC or not. And I didn't mean to say that no VC meant no AWD. I am curious if there is an easy way for me to confirm... without hijacking this thread too much. I'm running the hydraulic A442f transmission but I believe that I'm running the 1996 HF2AV case. From my understanding, it's the case that contains the VC... is that right? So, my thought is that I have the VC. Is there an easy way to check?
     
  17. IanB

    IanB SILVER Star

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    It is the TC that houses the VC if equipped, not the transmission, I wasn't clear on that. The TC is physically longer if it's the model with the VC, you may be able to tell from looking at it, or snap a pic and I can compare to mine.
     
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  18. Lumpskie

    Lumpskie

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    Good call @IanB
    Here's a picture I found for a VC case vs no VC case, for reference.

    [​IMG]

    I'll try to check after work. (if I can sneak a peak around my skid plates)
     
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  19. gummycarbs

    gummycarbs

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    Any situation where you get one wheel spinning. The VC acts like a limited slip differential for the transfer case. You'll probably never really notice it. The only time I did was when turning tight circles on gravel, where you'll see tire slip occasionally and feel a slight lurch. I was confused by this at first, thinking it was a binding Birfield!

    Jeep had a similar viscous coupling setup from 93 - 95 (NP249 Quadra-Trac). My 95 ZJ was amazing when I drove through a blizzard.
     
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  20. Lumpskie

    Lumpskie

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    Same here. My old Wagoneer NP229 has a VC that I used a lot on steep, icy hills back in CO. I could feel it work when a wheel started spinning. I could swear I get the same sensation in the LC but don't have any empirical data.
     
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