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NV4500 clunk

Discussion in 'Manual Transmission & Clutch' started by Frankenchevy, Jan 7, 2021.

  1. Frankenchevy

    Frankenchevy Lying Dog-Faced Pony Soldier

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    Thanks!
     
  2. bucket

    bucket Super Moderator Staff Member

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    Your crossmember should mount on top of the bottom frame lip... inside the 'C' of the frame. A K20 will have it mounted to the underside of the frame.
     
  3. Frankenchevy

    Frankenchevy Lying Dog-Faced Pony Soldier

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    Really? I have the flat CM and it’s always been mounted under the frame...

    I thought I’ve seen other cucv trucks the same way. I need to see if I can find some pictures.
     
  4. Frankenchevy

    Frankenchevy Lying Dog-Faced Pony Soldier

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    Just like this guy’s
    ED868A17-A1DC-46D6-9DA1-B58E068EDD18.jpeg
     
  5. Frankenchevy

    Frankenchevy Lying Dog-Faced Pony Soldier

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    The guy at the diff shop that did both of my axles said he’d put an ARB in for free if he got to keep the Detroit. Sounds pretty reasonable.

    edit: actually he said he’d owe me money after the work.
     
    Last edited: Jan 9, 2021
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  6. SquareRoot

    SquareRoot Full Access Member

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    @Frankenchevy .

    My x-member (w-style) mounts to the bottom of the frame rail.

    The flat part where the trans mount sits is exactly the same height as the bottom of the frame rails. The trans mount is 3 inches high.
     
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  7. bucket

    bucket Super Moderator Staff Member

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    My thought process isn't always correct. What I meant was, if you had the "W" style crossmember, it would mount up inside the frame.

    The flat crossmember used through '84, and all CUCV's had two styles. A more flat one for K30's and one that had more curve on the ends for the 10-20 trucks.
     
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  8. Craig 85

    Craig 85 Full Access Member

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    Granted I have a 205 and a "W" crossmember, but it's above the frame rail. All my K10/20's have been below.

    IMG_1486.JPG
    IMG_1612.JPG
     
  9. SquareRoot

    SquareRoot Full Access Member

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    It's impossible for my x member to mount inside the rails. There's only 1 set of holes in the frame that corresponds with mounting it underneath the rail.

    IMG_20210109_111138496_HDR_copy_3000x2250.jpg

    IMG_20210109_111147137_copy_3000x2250.jpg
     
  10. bucket

    bucket Super Moderator Staff Member

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    Right, but if it were a taller K30 frame, the holes would be there.
     
  11. SquareRoot

    SquareRoot Full Access Member

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    Ok, makes sense.
     
  12. GRK82

    GRK82 Junior Member

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    I have a NV4500 conversion in my 1985 K20. My trans is a 1993 GM unit. My tower would torque over and clunk my floor cut out. I had to make the hole larger. I know you’ve probably already thought of this and checked clearance. Have you checked your motor mounts? That could cause lots more movement than you would anticipate.
     
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  13. Frankenchevy

    Frankenchevy Lying Dog-Faced Pony Soldier

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    I was one of the things I considered. I checked clearance, but maybe I missed something. I’d be curious to see a truck with the 4500 in it from the factory to see how much perimeter clearance they have. How much space did you end up with around the edge?

    I have an experiment to conduct as soon as my lift is complete to see if I can isolate the clunk to the Detroit locker disengagement. If it is the culprit, it’s coming out.
     
  14. QBuff02

    QBuff02 I like Big Blocks and I cannot lie Supporting Member

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    I glanced through the comments briefly after watching the video.. Didn't see if it was mentioned but that trans/shifter tower seems to move around an awful lot in that hole between accelerate and decelerate in my opinion. I'd be rechecking the mounts and verifying they are tight/to spec. And i'd also take a good look at your motor mounts as well. Especially since you just put brandy new trans mounts in, you really need to install all new mounts together. New engine mounts= new trans mounts and new trans mounts= new engine mounts. The torque has to go somewhere and it will find the weakest link. Dad taught me 30 years ago "If you feel it in your hands it's somewhere in the front end, you feel it in the seat of your pants its in the driveline or rear end" and I've used that ever since. I've seen rearends with excess play make it sound like its up in the trans. and it could be in the motor mounts emanating back through the trans. I saw locker mentioned but figured i'd throw my .02 in the ring.
     
  15. Frankenchevy

    Frankenchevy Lying Dog-Faced Pony Soldier

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    All valid points.

    The motor mounts are new as well. I wasn’t super clear about that other than saying everything is new. At this point everything but the frame, body and axle tubes are new on the truck. Well, and I haven’t been through the transfer case yet, but the chain is tight and there’s no apparent slop in the bearings.

    There was no clunk pre-locker, then some sense of it loading unloading behind the th400 and now it’s full on behind the 4500. The guy who rebuilt my axles concurs that they are in fact clunky SOBs behind manuals. That’s why I’m going to test the theory with the rear driveshaft removed.

    I did check the mount torque again. Everything is really tight.
     
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