DYI: rebuilding/repair RT4wd Viscous Coupler

2»

Comments

  • Successfully disassembled my VC today. Used gentle heat with propane torch and prying with screwdriver to loosen and remove the metal covers. Only had to remove 2 retaining rings, the big one and the little one on the shaft at the opposite end. Coupler had not leaked, seals intact and unit filled with fluid. Fluid was almost black, presumably from metal particles. The coupler did work somewhat (was too stiff to rotate by hand), but would not reach full lock-up. When testing with the e-brake set and wheels off the ground, the engine would bog down but wouldn't die, then speed would recover. Need to get it cleaned up and replace seals. Don't really want to buy 5 (minimum order) of the big ones (at almost 6 bucks each) to get one, anyone want to sell one?

    LMK
    Thanks
    Craig

    edit:
    Belay my last, I found that the MOR-94.4X3.1V is available in single unit quantities. It is made with Viton (I believe), which is recommended for use with Silicone Grease. With discounts, the order, including shipping, totalled $26.69.
  • I recently rebuilt my VC using the Dimethylpolysiloxane (Dimethicone) available from Sage
    http://www.thesage.com/catalog/products ... icone.html

    The viscosity is too low, 1000 cS., the vc does not transmit torque, even though it feels quite stiff when turned by hand. Further research reveals that the 3 viscous coupling fluids listed by Dow Corning (which are no longer available according to the distributor I contacted) range from 10,000 cS to 88,000 cS viscosity. My research indicates that the fluid used in the synchro video is 100,000 cS, the metric measurement is equal to centistokes (cS). Note that, while they weighed the dimethicone carefully, getting it all into the VC is like trying to empty a bottle of refrigerated honey.

    I am still trying to find a supplier for the Dimethicone in the 60,000-80,000 cS range in a reasonable volume. So far i haven't.

    As for the correct volume, this is what I did. The air in the coupler is intended to allow for thermal expansion without damaging the seals. I reasoned that the maximum temperature of the coupling must not exceed the maximum temperature for those seals. The Buna-n seals have a maximum temp of 240 deg. F., so I filled the VC completely, then placed it with the fill holes up and open in an oven heated to 200 deg. F. and let it soak for about 3 hours (until the Dimethicone stopped oozing out). I placed a catch pan underneath so Heidi wouldn't know I was using her oven. I then took the VC out of the oven, poured out just a little more to bring the level below the bottom of the fill hole, then let it cool overnight. The next morning I reinstalled the plugs in the fill holes. This SHOULD provide enough expansion space without going over.

    The filling process will be very slow with the proper viscosity fluid, if and when I find it.

    I hope this makes sense.
  • GriftyGrifty Wagonist
    VIPwryann wrote:
    kylerwho wrote:
    Just to be clear what fluid did you use to fill the vc?


    Good question the correct answer may change based on feeback,

    however This is what I recommend:

    Its petroleum based so it may help expand the seals and get then to work for a little longer.

    Has anyone tried this oil yet? i just noticed my VC is leaking and i want to rebuild it, but since im in Australia i might not have access to a wide variety of oils.
  • Grifty wrote:
    VIPwryann wrote:
    kylerwho wrote:

    Has anyone tried this oil yet? i just noticed my VC is leaking and i want to rebuild it, but since im in Australia i might not have access to a wide variety of oils.

    I have located the correct silicone oil (Polydimethylsiloxane or PDMS, 100,000 cSt viscosity) and refilled my VC with it. It is now working properly. I had to buy a gallon of the stuff, the VC only needs about 9 oz, so I have the excess for sale.

    viewtopic.php?f=14&t=15384

    Of course, I wouldn't be able to ship to Australia for that price.
  • I hate to revive a dead thread. This is fantastic info - now I was wondering if the VC is the same on the '87 RT4WD? If so, I'll just be able to order the same part number o-rings.

    I'd like to think it's the same...can't see why Honda would have redesigned it the next year...
  • It should be the same, i dont see why not.
  • loiselle.m wrote: »
    I hate to revive a dead thread. This is fantastic info - now I was wondering if the VC is the same on the '87 RT4WD? If so, I'll just be able to order the same part number o-rings.

    I'd like to think it's the same...can't see why Honda would have redesigned it the next year...

    The 1987 RT4WD used a different VC
    [URL]http://www.hondapartsnow.com/Page_Product/PartDetail.aspx?catalogID=30&productID=4&yearID=26&doorID=3&gradeID=70&areaID=4&transmissionID=3&originID=-1&colorLabelIDs=-1&colorLabelID=-1&sectionID=&idAndImageID=5308 1474373[/URL]

    from the 1988 driveline:
    [URL]http://www.hondapartsnow.com/Page_Product/PartDetail.aspx?catalogID=37&productID=4&yearID=27&doorID=3&gradeID=79&areaID=4&transmissionID=3&originID=-1&colorLabelIDs=-1&colorLabelID=-1&sectionID=&idAndImageID=6480 1475545[/URL]
  • MrWhoopee wrote: »
    I have located the correct silicone oil (Polydimethylsiloxane or PDMS, 100,000 cSt viscosity) and refilled my VC with it. It is now working properly. I had to buy a gallon of the stuff, the VC only needs about 9 oz, so I have the excess for sale.

    viewtopic.php?f=14&t=15384

    I know it's a long shot but you still have that fluid left to sell?

    also I sent you a PM.
  • I know it's a long shot but you still have that fluid left to sell?

    also I sent you a PM.

    Yes, I still have some. Replied to PM.
  • Tanks Craig, too bad the 87 is different - I will have to do some scouting for the seals. Do you have any more of the fluid I could buy? I will send you a PM.

    -Mat
  • Just wanted to give a big thanks to Craig aka MrWoopee for meeting up with me to sell me enough Viscous fluid to do
    two couplers! Great seller.

    As soon as I get a little time I will rebuild the one in my car now as well as a back up. Ill post up results
  • Looking thru this thread, I realized that the complete info for the seals was missing, so here it is.

    Supplier: Hercules Sealing Products
    http://www.herculesus.com/

    1 ea. Shaft Lip Seal Hercules #MOS-38X50X7TC
    2 ea. Quad-ring Seal Hercules #QR-4325
    1 ea. O-Ring Seal Hercules #MOR-94.4x3.1-90D

    I still have some of the fluid left.
  • No one ever mention a video but I saw this today, might be helpful.

    https://www.youtube.com/watch?v=feD4D1quS0k
  • Questions for you guys who have rebuilt the VC:
    1. At what point did you decide that the VC's performance was poor enough to necessitate a rebuild?
    2. How has your rebuilt VC fared long-term? Any issues with vibration?
    3. Has anyone weighed a full or empty VC? This might be a good metric for evaluating a VC's health.

    My driveshaft is already apart so I could rebuild the VC relatively easily. However my VC hasn't shown any signs of imminent failure (passes the e-brake test and I can kick the back end out in the dirt, although I've noticed a strange fishy smell when the back wheels start getting power) and I don't want to 'fix' what isn't broken.
  • 1. I knew my VC had failed when I couldn't climb my snow-covered driveway with the '91, but the '88 would motor right up without hesitation.
    2. After 4 years, the VC in the '91 is still working properly, no issues, vibration or otherwise.
    3. Weighing is a thought, but requires removal and an accurate scale with sufficient capacity. The e-brake test should be sufficient.

    If your VC passes the e-brake test, I wouldn't worry about it. Put your efforts into prevention. Be sure your tires are all the same circumference. Get a flexible measuring tape over 70 in. long and check your tires whenever it's practical. Here's what I bought:
    http://www.ebay.com/itm/2X-Body-Measuring-Ruler-Sewing-Cloth-Tailor-Tape-Measure-Soft-Flat-118-300cm-/151815992403

    Put the largest in the front (they wear faster) and keep them within 3/16 in. of each other.

    HTH
  • Zwierzak89Zwierzak89 New Wagonist
    Guys how much oil is needed for coupler?
  • MrWhoopee wrote: »
    I have located the correct silicone oil (Polydimethylsiloxane or PDMS, 100,000 cSt viscosity) and refilled my VC with it. It is now working properly. I had to buy a gallon of the stuff, the VC only needs about 9 oz, so I have the excess for sale.

    viewtopic.php?f=14&t=15384

    Of course, I wouldn't be able to ship to Australia for that price.

    See above.
  • Zwierzak89Zwierzak89 New Wagonist
    oooo yeah now i see :D So it's about 260ml. It's funny but in Poland this oil is very difficult to find. But U can buy it in shop with RC models :D in 50ml bottles :D
Sign In or Register to comment.