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Transmission or transfer case failure

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  • Transmission or transfer case failure

    I picked up a recovered theft Typhoon at auction last fall, and found the truck to be in better shape than
    the auction house listed it. They said it had a bad engine, but it was just a loose power steering bracket
    making noise. I found most vacuum lines in sad shape and mis-connected. Some minor wiring issues,
    the worst being the stereo. The only 'major' mechanical issues found were missing front drive shaft and
    a fuel pump that had was not functioning properly.

    I work from home and was able to address all of these issue without putting many miles on it, and after
    fixing everything I found I prompted it to my daily driver. At which point I found one more issue, cruise
    control was not working and the ABS light would turn on at 15 mph and back off if I dropped below that
    speed. Research revealed that would likely be a vacuum release/TCC brake switch. I did not have one,
    but digging around under the dash I found what was left of one. I found only ONE new unit anywhere in
    the country and the seller wanted $300 for it. We negotiated and I finally only paid $45 for the $12 part,
    but at least now I had one. Cruise still did not work, but the TCC did and no more ABS light.

    That was two weeks ago. Last night while pulling away from a stop sign and approaching 35 MPH
    the engine revved up and the transmission acted like it was in neutral. I pulled over the tried each
    gear manually, including reverse. The truck will not move under it's own power in any gear, forward
    or reverse. I did not lose a driveshaft or a transmission fluid line. The fluid level is in the normal range,
    and is not burnt.

    I wrote this novel to provide as much info to help narrow the problem down. I am not sure if the t-case can
    fail in a manner to prevent any power being transferred. Note that in park the vehicle cannot be moved, which
    I think means the t-case is not the problem, but I may be misinterpreting that detail. I suspect an easy fix
    is not in my future, so I'd appreciate any guidance this group may have to offer.

  • #2
    If PARK holds, you're assessment is correct: It is NOT the transfer case.

    Interesting failure in that everything went away at once with no reported bangs or noise associated with the event. Some possibilities are trans pump rotor failure, broken input shaft/stripped drum spline, or broken output shaft (forward of the rear planetary where they usually break). If you were to put a pressure gauge on the trans, and run the static TV pressure tests, you could learn more about where you need to look when the trans gets out.


    • #3
      Thanks for the feedback. I have found out this morning that the last local transmission rebuilder has closed his shop,
      leaving me with a three hour drive each way to the next closest. So I think a new/reman is in the books as opposed
      to rebuilding what I have. I may run the pressure tests anyways to have a roadmap for a future rebuild.

      As to a bang or noise, there may have been a pop, but it was no Earth-shattering kaboom, and if it happened was lost
      over low volume stereo and the engine revving up at the same time


      • #4
        If your Ty still has its original transmission, you should try to keep it. Look at the passenger rear side rail, just above the pan gasket, between the last two pan bolts. There is a stamped number. Should be something like 2 (or 3) LHMXXXS. Where the leading digit is the model year, LHM is the SyTy 4L60 transmission, XXX= the Julian Day of the year built, and S = Shift (A, B, or C). Directly above the assembly stamp, on the horizontal surface is the VIN derrivitive stamping. You'll need a mirror to read it if installed. << 1992 ONLY. The 93 Ty VIN is "pin dots" on the LH rear body of the case. Very difficult to find even with the trans out of the truck. Impossible if installed. If you have a 93, the presence of "LHM" on the rail, and the indicators in the next paragraph are what need to be used.

        When the T-case is off, look at the rear output shaft, forward of the splines. The SyTy only has 2 radial grooves for ID of its special treated output shaft. With the pan off, the detent bracket for the shifter rod is gold irradiate plated (normal transmissions are silver). And the last SyTy identifier is the separator plate Identification. DT for 91 and 92, GS for 93. The id can be read with the valve body installed, but I forget exactly where it is. There aren't many places you can see the separator plate, so in the few where it is exposed, look there. The letters are about 1/4" high.

        Any 4L60 can be built up to work with a SyTy, especially a mild street build, but if you have the original bits, it's just cool to keep them with the truck.
        Last edited by DaveP; 03-28-2019, 09:21 PM.


        • #5
          OK, I bought a rebuild kit from ProBuilt, and had a local tech do the work. After delivering it to the shop
          to be reinstalled he thought he made a mistake and picked the truck up to remove the trans and double
          check. Turn out to be a false alarm, but did allow him to test the trans as part of the whole system and
          he reported the transfer case as failed. He reported 100% torque transfer to the front output, but I suspect
          he was dumbing it down for me and meant it was locked doing a 50/50 split.

          I think I read here or the other forum that new viscous units could be hard to come by, but not impossible.
          I am off to search for one, but if anyone knows where to get either a new viscous clutch assembly or a
          quality reman, I would sure appreciate it.


          • #6
            This link to a sticky post by Morgan should help you. Lots of great info.



            • #7
              Saw that, and it does help track down the part numbers. I thought I read that some had found the cobra v-clutch
              assemblies to be less than ideal. But it also appears that there may not be a lot of options either.


              • #8
                You initially reported that "Park Holds". Also, the VC can't fail in a way that no power is sent to the wheels unless one of the driveshafts is removed. And park shouldn't hold very well if this is what has happened. If you install the front driveshaft, the truck should drive normally again without changing the VC. It won't be great in snow, but just fine on the dry. Your VC has failed "open". Put a front driveshaft back in it, you'll barely be able to tell that anything is wrong.


                • #9
                  Great. Before the front pump failed (hub shattered in three large and multiple small pieces)
                  the truck drove fine with just the rear drive shaft. It took me a week to realize the front was
                  missing and it drove fine with both installed. So I won't worry about it and will use a different
                  vehicle for the once in a decade snow storm here in southern AZ


                  • #10
                    May I ask which ProBuilt kit you used? I'm looking at their kits to handle a mild build of 500-600 whp.


                    • #11
                      I think I went with the heavy duty, but cannot really comment on it. The local guy I had install it buggered it up several times, and I ended up with a rebuild just to get it moving


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