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    Testing your Transfer case without using the Jack Test

    A few years ago, i had a 2 ix parts cars that didn't run. i wanted to find a way to test the Viscus Coupling in the Transfer Case since the "jack test" wasn't an option.

    With some experimentation, here is what i came up with:

    Test #1: for complete non running or running car

    1) set the parking brake and/or chock both back wheels.
    2) put the car in neutral.
    3) jack up one of the FRONT wheels
    4) Spin the wheel by hand or better yet, use a beam style torque wrench on the center axle nut.

    you will need a fairly uncommon socket to accomplish this. i think the nut size is around 28-30mm? my inexpensive solution was to go to napa and buy a cheap 6 point thin wall 1 3/16" deep socket. i think this tool was around 10 bucks. you probably don't need a deep socket to do this test but you will if you are are checking a tc that is out of the car. (more on this below) also, most axle nuts are held on with a sheetmetal retainer that will probably impede you from getting a good grip on the nut with your socket. you can put a socket on one of the lug nuts instead but your torque value will be mathematically skewed by about 3".






    once you get the car lifted up and the wrench on the axle nut, you should feel a nice smooth fluid resistance as you rotate the wheel. in my case, i measured approximately 62ft/lbs as the wheel was spinning. unfortunately, i cannot find my beam style torque wrench and had to use the spring style. this type of wrench isn't very accurate for this test but perhaps its better than nothing. something to point out: it seems to me that the faster you spin the viscous coupling, the higher the torque rating. the reading i have above resulted from spinning the wheel about 1/4 turn in aproximately 2 seconds.

    if you can spin your front wheel with very little effort, this is an indication your vc is shot. unfortunately, this is probably the case for most of you.




    Test #2: Testing the Transfer case while it is out of the car

    you will need something to hold the front input shaft from moving. the easiest thing would be to stick the front driveshaft in the socket.

    in this case, it is imperative that you use a thin wall deep socket as pictured above. this is the only thing that will fit because of the alignment pin that sticks off the end of the rear shaft. even if you remove the guibo, a normal wall thickness socket won't seat on the nut.





    since i didn't want to mar up my driveshaft with a pipe wrench, i elected to step on the triangular end of the driveshaft in order to hold it in place. i used the same socket mentioned above to attach the torque wrench to the rear output.

    here is another "action" pic of me doing the test:



    once again, i couldn't find my beam style torque wrench so i used the shitty harbor freight spring type. in this case i measured somewhere around 18 ft pounds of torque. i guess this smaller value might make sense because when you test it on the car you have to go backwards through a 3.90 or 4.10 front diff. once again, the coupling has a nice fluid feeling resistance. as posted above, it seems to me that the faster you spin the viscous coupling, the higher the torque rating. the reading i have above resulted from spinning the rear output about 1/4 turn in aproximately 2 seconds.

    previously, i have had a few transfer cases with bad couplings. i found that i could insert the front shaft into the socket and use my hands to spin the case outputs against each other. if you can do this with yours, this obviously is an indication your coupling has failed.

    i certainly encourage all of you to contribute to this thread in any useful way possible. i will be happy to update the original post as contributions come in.


    this transfer case spec sheet comes from angus. you will note that it states the torque spec for a transfer case out of the car is 51ft/lbs @ 150 rpm. this works out to 2.5 revolutions/second. thus far, we have not figured out how to accomplish a reading at this speed.
    Attached Files
    Last edited by flyboyx; 06-19-2015, 11:55 AM.
    sigpic
    Gigitty Gigitty!!!!

    88 cabrio becoming alpina b6 3.5s transplanted s62
    92 Mtech 2 cabrio alpinweiss 770 code
    88 325ix coupe manual lachsilber/cardinal
    88 325ix coupe manual diamondschwartz/natur
    87 e30 m3 for parts lachsilber/cardinal(serial number 7)
    12 135i M sport cabrio grey/black

    #2
    that bottom test looks easy enough. I'll test my new one and post results. I have the same HF click wrench. they're supposed to be fairly accurate, actually.
    Build thread

    Bimmerlabs

    Comment


      #3
      I just did the bottom test side by side of a BAD one and GOOD one!
      NASA
      BMWCCA member
      PCA member 25yrs




      1991 318IS slick top
      1997 M3 sedan
      2001 325CI DD

      “whoever turns the wheel the least, wins"

      Comment


        #4
        Originally posted by nando View Post
        that bottom test looks easy enough. I'll test my new one and post results. I have the same HF click wrench. they're supposed to be fairly accurate, actually.
        it occurred to me after i posted this that it seems to me that the faster you spin the vc, the higher the torque reading. i'm going to update my initial post with this info.
        sigpic
        Gigitty Gigitty!!!!

        88 cabrio becoming alpina b6 3.5s transplanted s62
        92 Mtech 2 cabrio alpinweiss 770 code
        88 325ix coupe manual lachsilber/cardinal
        88 325ix coupe manual diamondschwartz/natur
        87 e30 m3 for parts lachsilber/cardinal(serial number 7)
        12 135i M sport cabrio grey/black

        Comment


          #5
          Hmm. how would we control for the speed?

          that makes total sense though. the faster you slip the VC, the more it will lock. maybe we can finally kill the myth that it works via heat..
          Build thread

          Bimmerlabs

          Comment


            #6
            Originally posted by nando View Post
            Hmm. how would we control for the speed?

            that makes total sense though. the faster you slip the VC, the more it will lock. maybe we can finally kill the myth that it works via heat..

            Yea,something i've been trying to get across for years , if heat changed the slip characteristics would BMW use this technology ,i think not.

            if you read the spec sheets on Polydimethylsiloxane its dynamically stable over a wide temperature range which is one reason its used for this application

            i posted the spec for the Torque value here some time ago ,right off a factory Tech sheet or manual
            and heres the link http://www.r3vlimited.com/board/show...ng+torque+spec
            Angus
            88 E30M3 X2
            89 325IX
            92 R100GS/PD
            :)

            Comment


              #7
              ok, here's an idea.

              Set your torque wrench to 51ft/lbs. move it as fast as you can and see if you can hit that. if it's too easy/fast then it's probably on the way out or dead.

              I think without a way to set RPM, there's no way to standardize it. I read an article years ago about a shop that used a lathe set at a specific RPM to measure a VC, but I'm not sure how you do that (not like you can put a torque wrench on it while it spins).
              Build thread

              Bimmerlabs

              Comment


                #8
                i saw the one you are talking about. i seem to remember it was from a subaru. i also seem to recall they had some special tools made up.

                angus, i added the spec sheet to this thread. thank you for posting.
                Last edited by flyboyx; 06-16-2015, 08:11 AM.
                sigpic
                Gigitty Gigitty!!!!

                88 cabrio becoming alpina b6 3.5s transplanted s62
                92 Mtech 2 cabrio alpinweiss 770 code
                88 325ix coupe manual lachsilber/cardinal
                88 325ix coupe manual diamondschwartz/natur
                87 e30 m3 for parts lachsilber/cardinal(serial number 7)
                12 135i M sport cabrio grey/black

                Comment


                  #9
                  OK now folks - no getting clocked in the head by a flying torque wrench - LOL

                  Awesome work!!! Much needed testing methods!!!

                  Comment


                    #10
                    This is why I love this site..

                    Comment


                      #11
                      How about fabricating a knob to attach to the torque wrench handle. I bet after testing a few good ones, one would develop a "feel" for the condition.

                      Comment


                        #12
                        Decided to try this myself on an unknown unit (believed to be good - but who the hell knows)

                        Loaded up a manual trans case onto the work bench and placed the drive shaft into the Monster vice (I bought last weekend..weeee)


                        Next I tried spinning it by hand and it took some force to spin the shaft - does not spin easy..

                        Pulled out the trusted Harbor Freight clicker and basically I was getting around the 18 foot pounds with an even steady slow pull - If pulled faster it clicked. I could if I tried to just move it very slow I could at 10 foot pounds..

                        Ok - so I pulled out the spring inch pound and measured the torque of the initial pull to get it to move - and I was reading around 50 inch pounds (around 4 ft pounds) -

                        If I tried to follow what Nando suggested to pull has fast as I could (limited to only 45degrees of pulling action) - starting from a dead stop - to see how fast I could spin it - I Maxed my gauge at 600 inch pounds (or roughly 50 ft pounds of torque) although it was really hard to tell exactly what the number was as I didn't have enough rotation to get a steady number.

                        Disclaimer - the spring gauge is old and hasn't been calibrated -yada, yada - so I take these measurements as an approximation..

                        However - I can see that "steady pull" would be the issue - that is why I tried to measure what the initial resistance (force) it took to begin rotation..

                        The TC acts as though it meets the requirements - meaning the force it takes to rotate faster grows - versus spinning one with no resistance..

                        So I wonder if this is good or not..?
                        Attached Files

                        Comment


                          #13
                          i would flip that setup around so you can get a clear 360 deg of rotation at rear output flange with the Tcase on a separate table strapped down and front output locked in vice with rear output hanging over edge of an appropriate height table . i think you need to get a smooth consistent 2.5 turns a second (2.5 X 60 sec = 150 RPM,should be close to do-able) to get a good reading on the beam torque wrench to have a better reading than just 45 deg rotation, as stiction will affect initial reading from a stop and i think a couple rotations would be needed for VC fluid to start locking up.
                          Angus
                          88 E30M3 X2
                          89 325IX
                          92 R100GS/PD
                          :)

                          Comment


                            #14
                            honestly, i think it would be all but impossible to spin the tail stock @ 150rpm with a hand wrench. the length of the torque wrench handle is about 20". this x 3.14" x 2.5 = 157"/second or about 13 feet!

                            i do think it might be possible to spin it momentarily pretty close to that speed. the problem is that it would be impossible to quantify the rpm.
                            sigpic
                            Gigitty Gigitty!!!!

                            88 cabrio becoming alpina b6 3.5s transplanted s62
                            92 Mtech 2 cabrio alpinweiss 770 code
                            88 325ix coupe manual lachsilber/cardinal
                            88 325ix coupe manual diamondschwartz/natur
                            87 e30 m3 for parts lachsilber/cardinal(serial number 7)
                            12 135i M sport cabrio grey/black

                            Comment


                              #15
                              http://www.omega.com/pptst/TQ513.html

                              http://www.omega.com/pptst/DFG35.html

                              Come on guys, everyones got one of these things attached to their $10,000 lathe nowadays, catch up.

                              But seriously, I was tryin to come up with a way to measure the torque as well, does anyone have a way to spin it at 150 rpms? If you could, you could just put a torque wrench on the stationary side and measure the torque on it while the other side spun.

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