88GMCtruck's 98 Silverado Towpig Build: "Black Fox"

Discussion in 'Member Trucks' started by 88GMCtruck, Aug 16, 2013.

  1. Supercharged111

    Supercharged111 I'm Awesome

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    Well I'm feeling lazy. I've read the majority of this thread, but what I can't recall is how big of a tire did you end up on and did you require spacers between the wheels to fit the whole hot mess?
     
  2. Biggershaft96

    Biggershaft96 Resident 4l60e killer

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    He is running 255/85r16 coopers and he had to put a spacer in the rear but i cant remember how wide it is.
     
  3. 83GMCK2500

    83GMCK2500 I'm Awesome

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    1.5", same as my truck.
     
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  4. 88GMCtruck

    88GMCtruck I'm all 8-Luggy!

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    Wow it's been awhile! Had quite the busy holiday season, of course right in the middle of it I started hearing a whining sound while driving... A couple hundred miles later it was WAY louder than it should be. So, time to diagnose...

    After all the transmission problems, I'm pretty in tune to figuring out sounds. So first was the easy test - is this trans, transfercase, driveline or rear end... Shift the transfercase in neutral and "drive" the trans. There is no other way to describe this other than watching the video.

    th_BC895109-E6B9-4F17-9A71-491AFA333E5A.jpg

    So, very obvious that the transfercase has something wrong with it. Pulled the fill plug to check fluid, yup, plenty. Color though..... oh no.

    F92A10EF-D0A4-4485-AA44-29890EFC1B28.jpg

    Due to the holidays, the cold temps outside, I decided to just buy a transfercase.... That turned into a disaster in itself. My truck is a K3500. And for those who aren't familiar... K3500 trucks use a Borg Warner Transfercase with a PTO provision and fixed front and rear yolks. Sounds straight forward right? Nope.

    GM used 3 BW cases in these trucks. BW1370, BW4401, and BW4470. My truck has a BW4401. It's a predecessor of a BW1370 (they actually share a ton of parts, and half of the case even says 1370 on it). They used the BW4470 in Chassis Cab trucks which were rated at 12,000 GVW. There is also a heavier version of the BW4401, for crewcab longbed trucks outfitted with RPO 9D6 (11,000 GVW). Both the BW4401 9D6 and the BW4470 use a 1.5" wide chain and gears as opposed to the 1.25", and the BW4470 has a fixed oil pump housing plate which the others do not have. To make it even more confusing up front there are flange (early) and fixed yolk (late) outputs, and in the rear there are slip yolk outputs for early regular cabs, and fixed yolks for the rest.

    Oh, did I mention this transfercase has an electromagnetic front driveline synchronizer that is tied into the front actuator? Yup. And because of this it uses a different 4wd harness than the rest of the NP241 trucks and has a firewall mounted relay to control it.

    Basically, this was 2 weeks worth of research, and a couple junkyard trips. The cases are like, $1,200 for a rebuilt one, and run $600 or so for a used one, if you can find one locally. They are just simply not common. I thought I had one at a junkyard locally, ended up spending about 4 hours looking through tons of transfercases only to find an early flange front output style, and they couldn't locate the correct one. Another yard had one, and Devin (@83GMCK2500) went to look at it for me, but it turned out to be a BW4470 (at this time I didn't fully know the differences between them). The fixed oil pump plate added about 1" to the length, so with those measurements I determined I did have enough slip yolk useable to swap that larger case in my truck, so home it came.

    BW4470 VS BW4401
    DDBE86FC-930D-47C5-B238-756383FD8EED.jpg
    10A708CF-D76A-4D4C-A47C-24FBDE58E400.jpg
    65EF715E-C649-4AA7-A879-E9A2BEAB19F5.jpg

    I haven't gotten into it yet, but here is the case out of the truck, in neutral.... Something got fried in there.
    th_EEE36C05-9263-4797-AF30-9F7BEDF297C8.jpg

    Oh, and I forgot to mention, as much of a PITA it is to pull the transfercase in this (they are about 2x as heavy as a NP241), it was a bit of a blessing in disguise/potential nightmare. Upon myself inspecting things, I found the nut on 5th gear had backed off on my NV4500 and the gear was only 1/2 engaged... Mind you this only has 6,000 miles on it from brand new.......
    43711667-54EE-417C-98D7-FDFC3DF8EBA9.jpg
    A213C6C0-C332-40C5-AE93-1D15B97AB8DE.jpg

    I tapped the gear back on, installed the spacer, the OEM spring washer (which was not installed by the trans shop), and a replacement nut with loctite.

    Been working fine since.

    Another little upgrade, Devin gave me a front receiver he scored at the junkyard.
    D58F2295-B38E-49F5-B7E2-AF4E962F3571.jpg
     
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  5. adray96

    adray96 I'm Awesome

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    I've said it before earlier in the tread, but I'm going to go ahead and said it again: I absolutely love this truck. I've never wanted a dually so bad until I found this thread, haha. I literally have a picture or two of it saved in my phone to show friends my ideal truck.

    It sucks about the transfer case, but glad you got it figured out


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  6. 83GMCK2500

    83GMCK2500 I'm Awesome

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    To recap...

    "tapped it back on" Hah! ...again, yay having the NV-4500 tool kit.

    Yes, heavy bitch it was.

    WHY IS THERE NO INFORMATION ABOUT BORG WARNER TRANSFER CASES!? F---!

    Glad you like hitch.
     
    Last edited: Jan 10, 2017
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  7. 88GMCtruck

    88GMCtruck I'm all 8-Luggy!

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    At least, if people search and find my thread, they will at least get some idea about these cases.
     
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  8. dave_erald

    dave_erald I like cheese

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    I remember reading a little bit on these things, and i think their may still be a parts website that has good info on these cases.

    32 spline outputs are nice and bigger chain is always good.

    So rear shaft got changed than?
     
  9. dhunt

    dhunt Newbie

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    Can't ever catch a break. Gives you an excuse to drive the 88


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  10. Biggershaft96

    Biggershaft96 Resident 4l60e killer

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    I think he mentioned the slip yoke had enough play that the stock shaft would work.
     

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