Viscous Coupler info.

13

Comments

  • suntrana45 wrote:
    This may be redundant but have you checked to make sure the 4 wheel drive shift lever (towing disengage) is in the proper position for 4 wheel drive.? It is located on the top of the transmission (very hard to see, look slightly behind the distributor and down to the top of the tranny), there is a 10mm nut that you have to loosen (Caution: just a couple of turns) and then the other 10mm bolt can be turned to engage/disengage 4 wheel drive. Just a thought.
    Yes i was actually thinking the same thing. I haven't checked it yet. I did try to locate the lever once, out of curiosity, but I was in a hurry. I plan on looking at this tomorrow afternoon. I was lucky enough to get my wagon with the original owners manual (with the key code written in it too!) and I read through the whole thing the first night I had my car. It explains how to disengage the 4wd for towing, but the diagrams are kind of crappy and don't really explain EXACTLY where the lever is. Plus it says the lever is orange or something, and everything i can see has a nice layer of brown dirt on it.
  • suntrana45suntrana45 Band Wagon
    Kinda "orangey" or sorta "yellowish" depending on amount of dirt and grime, I used a 1/4" socket set (smaller footprint), and if I remember about 12" of extension and a deepwell 10mm socket,( a little easier to fit on nut). Just accidently found this most wonderful, long awaited, fantastic submitted article on the VC coupler itself with tips and tricks on how to actually work on the damn thing, complete with pictures, suggested fluid replacement and where to buy same. I have been looking for several years for this most appreciated info, hope it helps you also. The VC is actually very easy to remove from the vehicle, just make sure you have proper jack stands in place and emergency brake set. By the way just about everything under there is very heavy, especially if it is supported just by your fingertips (personnal discovery), good idea to wear goggles or safety glasses, (another discovery). Take it easy and take care.
    viewtopic.php?f=7&t=11567
  • Yeah thats the thread I was talking about yesterday. Seems pretty helpful. I'm curious about the fluid he used. 75w-90 gear oil I believe. And if I understand, the VC is supposed to use a Silicon-based fluid because of it's distinct thermal expansion properties, so I wonder if the gear oil is really a good choice or if the silicon fluid should be used.

    Thanks again for the info, you've been very helpful.
  • suntrana45suntrana45 Band Wagon
    Somehow the "threads" I am watching don't seem to link together.
    Great, wonderful, fantastic write up. I did some cross referencing on the fluid, as near as I can tell ( add several grains of salt), the recommended fluid is a Silcone based liquid (from the German website) was listed as 1000 cSt, this would convert out to about 250 weight gear lube. I am not sure what the SAE weight of Lucas product was or where you would find this information.
  • suntrana45suntrana45 Band Wagon
    Would agree on the "Silicone" oil it does have some very unique properties, temperature expansion and I think it has a tendency to adhere to surfaces a little differently than petroleum based products. I also noted he used a large air driven impact to remove the nut on shaft, this would probably be a tough one for the "shade tree" mechanic to get loose. Would guess the torque requirements for this could be looked up on a chart by size of shaft. Really appreciate the efforts he went through to "solve" this mystery repair problem.
  • I'm sure the torque spec for that big nut is in the service manual. I'll look later, I have it saved on my computer somewhere.

    I spent all day fixing someone else's car today, so I didn't get much time to look at my own. I DID find the Disengagement lever, and it WAS in 2WD mode. The problem is, there didn't seem to be a lock bolt. Upon further inspection, I found that the bolt is broken off, with half of the bolt still in the hole. :-( Damn, more headaches.
  • suntrana45suntrana45 Band Wagon
    Oh NO, Mr. Bill, sounds like someone before you didn't use the old "Lefty Loosy" "Righty Tighty" method. I remember the warning note that states, "Don't loosen the locking bolt to far, because is can be a major effort to repair", or some such. On the wagon I am trying to maintain at the moment I can't seem to get the lever to engage the four wheel selection, it has a "spongy" type rebound when I try to engage it, and something tells me that isn't normal. Wonder what your chances would be to try and spot or tack weld something to whatever is left of the bolt, long shot I know. You might be able to figure out another method of holding, or wedging the lever in the 4 wheel mode assuming you can move the lever.
  • JakerJaker familEE
    Chances are the broken piece of bolt is not seized and you could probably unscrew it relatively easily. Then again, I have been wrong before!
  • suntrana45 wrote:
    Oh NO, Mr. Bill, sounds like someone before you didn't use the old "Lefty Loosy" "Righty Tighty" method. I remember the warning note that states, "Don't loosen the locking bolt to far, because is can be a major effort to repair", or some such. On the wagon I am trying to maintain at the moment I can't seem to get the lever to engage the four wheel selection, it has a "spongy" type rebound when I try to engage it, and something tells me that isn't normal. Wonder what your chances would be to try and spot or tack weld something to whatever is left of the bolt, long shot I know. You might be able to figure out another method of holding, or wedging the lever in the 4 wheel mode assuming you can move the lever.

    I slid the lever over into 4WD and just lieft it. So far it hasn't popped out, but I haven't been in a situation where 4WD would be engaged. It is supposed to rain a bit later this week though.... So i guess we'll find out.

    As far as moving the selector, here's what I had to do.

    FIRST!!! Park on level ground and block the wheels, but leave enough room so the car can roll back and forth a little bit. I only needed to roll a few inches, but yours may be more. I used two phone books. Just don't roll it too fast.

    Put the shifter in Neutral, and release the parking brake. Engine off.

    Now atand in front of the car and reach down with your left arm to the 4WD lever (this is much easier with the intake tube removed) and gently push the lever towards 4WD while using your right arm and your legs to roll the car back and forth. You could also use a buddy to roll the car, but whatever.

    I only had to roll mine forwards like 2 inches and it slipped right in the first time, with minimal effort.
  • Jaker wrote:
    Chances are the broken piece of bolt is not seized and you could probably unscrew it relatively easily. Then again, I have been wrong before!
    I would imagine it would have to be seized to break in the first place.... I was considering trying to cut a phillips head into it and use an impact screwdriver to try to back int out. don't know.
  • suntrana45suntrana45 Band Wagon
    Sounds like your problem, while a bummer, may not stop the 4 wheel engagement, fingers crossed. Thanks for the tip on moving the selector, I tried "rocking" the car but had it in gear and pushing on the bumper, Neutral position of shifter makes more sense.
    I have been using a mixture ( 50/50) of charcoal starting fluid and automatic transmission fluid on my old Ford tractor to break loose old rusty bolts, seems to work better than WD-40, PB Blaster etc. if you can occasionally spray the lever assembly for a few days it may help break loose the "stuck". On another note, not sure what shape your wagon is in, but one of mine rusted out at the rear wheel wishbone, the "A" frame collapsed and the wheel folded out, luckily I was just backing out of the parking lot when it happened.
  • I think your only chance of getting the broken bolt piece out of the hole is with a screw or bolt extractor. This tool has saved me quite a few times on broken rusted bolts. However, I don't know how you would be able to do it with the transmission still in the car as you need to drill a pilot hole and use the extractor to back it out...
  • suntrana45suntrana45 Band Wagon
    Extractor, Hex Head Fastener, 5/16" (8mm), 3/8" square drive, this is from Snap-on, I have had really good luck with the larger model, it really "digs" in as you are turning it counter clockwise, of course that is if you can get to it. Biggest problem, of course, is getting a clear angle of attack.
  • JakerJaker familEE
    I would imagine it would have to be seized to break in the first place.... I was considering trying to cut a phillips head into it and use an impact screwdriver to try to back int out. don't know.

    Not if it broke from overtightening!
  • suntrana45 wrote:
    Sounds like your problem, while a bummer, may not stop the 4 wheel engagement, fingers crossed. Thanks for the tip on moving the selector, I tried "rocking" the car but had it in gear and pushing on the bumper, Neutral position of shifter makes more sense.
    I have been using a mixture ( 50/50) of charcoal starting fluid and automatic transmission fluid on my old Ford tractor to break loose old rusty bolts, seems to work better than WD-40, PB Blaster etc. if you can occasionally spray the lever assembly for a few days it may help break loose the "stuck". On another note, not sure what shape your wagon is in, but one of mine rusted out at the rear wheel wishbone, the "A" frame collapsed and the wheel folded out, luckily I was just backing out of the parking lot when it happened.
    Man that really sucks. No, my wagon is definitely not rusted out. It's actually in pretty good shape, just had some half-assed mechanical work done to it apparently.
  • A few interesting things today. First, I was doing a little work to the rear brakes, and I noticed that with one rear wheel off the ground, parking brake off, car in gear, the wheel didn't want to turn. I would turn, but it took considerable force, like it was encountering resistance from viscous fluid. That got me really hopeful that the VC is still in working condition.

    It rained tonight too! I hit the same exit ramp, and gave it all hell in 2nd gear around that tight turn. As soon as the front started to break away, I noticed a significant reduction in wheelspin, and almost no understeer. In fact, the first time I let out of the throttle, I even felt a little oversteer.

    Did you ever get yours into 4WD Suntrana45?
  • suntrana45suntrana45 Band Wagon
    Not yet, really glad to hear yours seems to be working, I think I would check the outside of the VC for any "leaks", looks like you might have found a simple way of "testing" the VC also.
    At the moment my 99 Civic is down for timing belt problems and since that is a daily driver my "hobby honda's" will have to wait for awhile. Never have figured out why the little wagons were not more popular, for me it is a great little utility vehicle. My experience, for what it is worth, never, ever let a Honda overheat, the distributor "ignitors" were a source of trouble and the Main Power Relay was undersized and the solder joints were pathetic.
  • suntrana45 wrote:
    Not yet, really glad to hear yours seems to be working, I think I would check the outside of the VC for any "leaks", looks like you might have found a simple way of "testing" the VC also.
    At the moment my 99 Civic is down for timing belt problems and since that is a daily driver my "hobby honda's" will have to wait for awhile. Never have figured out why the little wagons were not more popular, for me it is a great little utility vehicle. My experience, for what it is worth, never, ever let a Honda overheat, the distributor "ignitors" were a source of trouble and the Main Power Relay was undersized and the solder joints were pathetic.
    I agree, my old 91 civic hatch had those exact same problems.
  • ban hammer
  • SkeletorSkeletor Band Wagon
    I want to rebuild my viscous coupler. It still works but not feeling as strong as it used to. I was wondering if I disengage the 4wd can i remove my whole propeller from the tranny to the rear diff still drive my car while i rebuild it or will something be thrown off?
    Also when cleaning the viscous coupler what is the best product to use? is the viscous coupler fluid resistant to certain types of cleaners since it is not petroleum based?
    I love my RT
  • AbideAbide Council Member
    it runs just fine in 2wd mode with no shaft. drove mine without it after i got it for 5 months
  • Might be a good idea to take a few digital photo's of all running gear and where needed put punch marks or match marks to aid in reassembly, this might save a lot of time as far as balancing issues. Those ziplock bag are great for small parts and you can write on them as to where they came from. Also from the school of hard knocks is make a list of what order you take things apart, made the mistake of "bagging" parts, etc, but then forgot the reassembly order, cost me hours and hours of frustration. If possible apply lots of penetrating oil a few days before dis assembly and always wear safety goggles, (saves hours of washing gunk out of your eyes)..... :) :)
  • suntrana45 wrote:
    Might be a good idea to take a few digital photo's of all running gear and where needed put punch marks or match marks to aid in reassembly, this might save a lot of time as far as balancing issues. Those ziplock bag are great for small parts and you can write on them as to where they came from. Also from the school of hard knocks is make a list of what order you take things apart, made the mistake of "bagging" parts, etc, but then forgot the reassembly order, cost me hours and hours of frustration. If possible apply lots of penetrating oil a few days before dis assembly and always wear safety goggles, (saves hours of washing gunk out of your eyes)..... :) :)

    I totally agree with everything you said. Been there, made all those mistakes myself! haha!
  • SkeletorSkeletor Band Wagon
    Just got my seal and fluid. Prob going to be a while before i do it because i am moving. I will definitely do a write up when i do it though. Thanks Lavoy
  • Just finished refilling my VC with 100,000 cSt PDMS (polydimethylsiloxane, also known as dimethylpolysiloxane and Dimethicone). Man that stuff is thick! On the upside, it's really nice on your skin. As lavoy1 (hereinafter known as He Who Shall Remain Nameless, HWSRN) stated in his video, you have to disassemble the plate stack in order to fill the VC, the PDMS is just too thick to fill by allowing it to flow down thru the plate stack. I took some pictures and measurements while I had the stack apart.
    378.jpg

    I will refer to the slotted plates with splines on the OD as "A" plates, the plates with round holes and splines on the ID as "B" plates.
    Note the little wire ring below the plates, it serves to keep the B plates separated, maintaining clearance for the A plate. There is one of these rings between each pair of B plates, the ID of the A plate is large enough to clear the ring, allowing it to "float" between the B plates. The ring is made from .044 dia. (1.1 mm) spring steel. The A and B plates are .027 (0.7 mm) thick. This means that the B plates are .044 apart with a .027 A plate between them. This leaves a clearance (on each side) between the A and B plates of .008 (.044 -.027=.017/2=.0085) (.2 mm). This is about the thickness of 2 sheets of copy paper, much too narrow for something as thick as honey to flow into. When reassembling the stack, be sure that there is fluid between the plates as you drop them in, then press each one down firmly before adding the next one. I had some difficulty getting the stack compressed enough to get the retaining ring in place.

    HWSRN stated in the video that he was told that the PDMS expands very little up to 400* F. From the supplier's website, I find the coefficient of thermal expansion to be .00094 cc/cc*C. That is, for every degree C of temperature rise, a cc (ml) will expand .00094 cc. With a temperature rise of 100* C (from freezing to boiling water), the expansion is .094 cc/cc. This equals 10.64% expansion (1/.094=10.638). While your VC may or may not reach the boiling point of water, it is clear that the expansion with heat is significant. Since liquids are not compressible, allowance must be made for expansion or the PDMS will force its way out past the seals, potentially damaging them. The 10.6% expansion seems to agree with the figures I have found elsewhere on the Web regarding the percentage of air (10-15%) needed when refilling a VC. I chose 100* C temperature rise based on the maximum operating temperature of the Buna-N quadrings used as shaft seals (115* C./ 240* F.), assuming that the temp of the VC will not exceed that figure.

    I have posted this elsewhere, but I'll post it again here.

    Since I didn't know how much fluid capacity the VC has, I had to find another way to achieve the proper air volume. I decided to fill the VC completely, close it up with a vent hole open, then heat it in the oven at 200*F (93*C) for a few hours allowing the PDMS to expand and ooze out thru the vent. Once this was done, I poured off just a little more, then let the VC cool overnight and draw air in. After it was cool, I sealed the vent and finished reassembling. The first time I did this, I removed one of the Torx head screws at the end of the VC opposite the shaft. This was a little difficult because it is opposite the open end and makes it hard to close the unit and seat the big retaining ring. This time I knocked out one of the ball-bearings that are staked into holes in the large cover plate. I believe these were probably vents used during the original filling. This allowed air to escape as I seated the end cap and big retaining ring. Once I was done heating the VC, I poured off the excess PDMS, put the ball back in the hole and staked it with a center-punch.

    Sorry for the long post, there's a lot going on here and I don't want anyone else to have to redo theirs like I have.
  • bam-bambam-bam Council Member
    Thanks for posting. I've been reading around as well, found some good discussion on VW Vanagon sites. I seem to remember something like 86 percent fill .

    I have 3 couplers, at least one is leaking. I bought seals and fluid enough for 2.
  • CharbCharb Administrator
    Nice work guys! Keep this thread updated... very useful for newbies!
  • :shock: I have found more information on some of the issues we are having with our "Vicious Viscous" Couplers. Please take with several grains of salt or salt substitute.
    VC's life span seems to run between a low of 40,000 miles (60KM) to a high of 125,000 miles (200Km). Depending on several factors, the number one cause of VC fluid failure (turns to a gel like substance) is "Stress", this stress is most often caused by: Improper tire pressures, Different tire diameters (tires should be within .08in (2mm) to .16in (4mm). Tire tread depth should be within .04 to .08 in (1 to 2 mm) *These seem to me to be pretty "tight" as far as wear but the overall idea is to make sure all four tires are as close being the same as possible..
    Naturally the best bet would be never, ever mix tire brands or even different models from the same manufacturer. Needless to say it would probably be really hard on a VC to use the Mickey Mouse spare for any distance.
    I read a small excerpt from a Mechanical text book that may help in solving the difficulty in determining the proper fluid level when refilling, it seems these little buggers are filled by weight not volume, of course this process would put it out of reach for the "shade tree" mechanic, other sources range from completely full, to a critical 80% to 86% with the optimum being 84% to 86% full.

    Another little nugget was the plate construction, the plates have microscopic "burrs" on their surfaces when they are manufactured again something we couldn't do at home.
    Some of the failure indications were; Hard steering, Tires "scuffing" on turns, especially backing up, When turning a sharp corner it feels as though you were applying the brakes. These symptoms must be addressed as soon as possible because a VC failure can lead to really, really extensive damage to everything from the trans axle to any or all of the running gear. The fluid also, over time, picks up minute metal particles hence the need for thorough cleaning when attempting rebuild. It looks as if the actual rebuild process will very greatly from vehicle to vehicle because of previous usage and internal wear on the plates. And to state the obvious, isn't it sad that there isn't a "standard" VC unit that could be shared by all manufacturers, or at least narrow down the differences between them? Hope this information will help all in efforts to keep the little guys running and on the road.
  • suntrana45 wrote:
    :shock: I have found more information on some of the issues we are having with our "Vicious Viscous" Couplers. Please take with several grains of salt or salt substitute.
    VC's life span seems to run between a low of 40,000 miles (60KM) to a high of 125,000 miles (200Km). Depending on several factors, the number one cause of VC fluid failure (turns to a gel like substance) is "Stress", this stress is most often caused by: Improper tire pressures, Different tire diameters (tires should be within .08in (2mm) to .16in (4mm). Tire tread depth should be within .04 to .08 in (1 to 2 mm) *These seem to me to be pretty "tight" as far as wear but the overall idea is to make sure all four tires are as close being the same as possible..
    Naturally the best bet would be never, ever mix tire brands or even different models from the same manufacturer. Needless to say it would probably be really hard on a VC to use the Mickey Mouse spare for any distance.
    I read a small excerpt from a Mechanical text book that may help in solving the difficulty in determining the proper fluid level when refilling, it seems these little buggers are filled by weight not volume, of course this process would put it out of reach for the "shade tree" mechanic, other sources range from completely full, to a critical 80% to 86% with the optimum being 84% to 86% full.

    Another little nugget was the plate construction, the plates have microscopic "burrs" on their surfaces when they are manufactured again something we couldn't do at home.
    Some of the failure indications were; Hard steering, Tires "scuffing" on turns, especially backing up, When turning a sharp corner it feels as though you were applying the brakes. These symptoms must be addressed as soon as possible because a VC failure can lead to really, really extensive damage to everything from the trans axle to any or all of the running gear.

    I have run across this same material in various places. Matched tire diameters is one of the most critical factors. STE Couplers, who rebuilds VCs for almost everybody but us, sells a "Stagger Tape" for measuring the circumference of your tires.
    http://stecouplers.com/recharge/modules ... x.php?id=8

    They state that variation of more than 3/16 inch on circumference (less than 1/16 diameter) is hazardous to your VC.
    As for tread depth, it's harder to see what effect that might have, although .04 is down at the wear bars anyway. Just be sure to check your tires and rotate them regularly (largest in front).

    Once you've established the proper amount, filling by weight is the only accurate way. So much of the PDMS sticks to the container there is no way to accurately determine the volume transfered. While filling my VC, I did my best to determine the weight of the fill. I started by weighing my container of PDMS before filling, then again after to determine the amount of the initial fill. I then recovered what was expelled from the VC during the heating process. These numbers are very rough. The PDMS sticks to everything, so the amount I calculated will be high. The initial fill was 259.4 g., the amount recovered after heating was 14.2 g (closer to 5% than 10%, I can't be sure how much air was still in the VC when I closed it up), final fill weight 245.2 g. (8.65 oz.) Remember, these numbers are very rough, but give a good idea as to how much fluid you will need to start.

    The stuff about "microsopic burrs" is interesting. To have these burrs on both sides, the plates would have to be ground flat (i.e. surface, blanchard or double-disk ground), leaving the sharp edge on the holes and slots. Our plates have not been ground, the surface would show tell-tale grinding marks, or they have been tumbled in an abrasive media which would erase the grinding marks and the burrs. While these burrs could possibly increase the drag between the fluid and the plate, they would likely be worn off fairly quickly in use. It seems unlikely that a professional rebuilder would have the means to recreate these burrs (regrinding the plates would change the thickness, throwing the whole stack height off) and I'm quite certain they are not replacing the plates with new ones. I believe the "microscopic burrs" are a theoretical concept or a myth, perhaps intended to discourage attempts at doing the work yourself.

    "Gellation" and the failure indications listed seem to be associated with AWD vehicles that utilize a pre-load on the coupling. Gellation would cause the VC to behave as if it were solid, causing the symptoms mentioned. Running mis-matched tires will cause this behavior, I found this out by personal experience. Our little babies just seem to quietly lose their function after the fluid escapes. We aren't even aware of it until we try to climb a snow-covered driveway. Interestingly, my VC showed no signs of leakage, yet only had about 1/2 the fluid it should.

    I'm about due to find something else to obsess about. :lol:
  • I love this thread!
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