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Thread: NP208 Issues

  1. #1

    Default NP208 Issues

    1985 Chevrolet Silverado 4x4 regular cab short box.

    I just finished swapping out my blown turbo 350 transmission with another one, and it works great compared to my last one! But, i have another issue now. I wanted to see if 4x4 would work last night when i got done. So after my first test drive with my truck, just light driving up and down road, i brought it back in the yard, my yard has gravel on it, so tires spin, very, very easy. I wanted to see if 4x4 worked, so i got out, locked the hubs, put the tranny in neutral, and i have the manual shifter for my transfer case, so i dropped it all the way down to 4-low, i wanted to see if it would spin all 4 tires. Which can be done very easy in my 2002 silverado. So i get it in 4-low, drive around 20 feet to make sure its in, i stop, and then give it some gas. And i can hear an awful TUNK TUNK TUNK coming from under the truck. I refilled the transfer case properly, i bolted the front drive shaft down right, i made sure both hubs were locked. I also tried this in 4-hi, and it did the same thing.

    Anyone got a clue what it could be? Hopefully i don't need to drop it out and get the damn thing rebuilt.
    2002 Chevrolet Silverado 1500 z71 1985 Chevrolet Silverado k10 2006 Chevrolet Silverado 2500hd 6.6l LLY Duramax
    6.5" BDS Suspension Lift Edelbrock Carb & Polished Intake Manifold & Valve Covers NAPC Race Transmission & NAPC Built Transfer Case
    EFI Live Comp Cam and Valvetrain Snow Performance Methanol Injection
    35" Toyo Open Country Mud Terrain on 18" Ion Alloy 179's Headman Long Tube Headers and True Dual Exhaust FASS 150gph Titanium Series Pump
    AirAid Cold Air Intake with K&N Dry Filter & AirAid PowerAid Throttle Body Spacer 2" Suspension Lift 33x12.50r15 Tires EFI Live & AFE Stage 2 Intake
    Pacesetter Long Tube Headers with Cats Gone True Dual Exhaust FlowPro 3.73 Gears Yukon Grizzly Locker with Mag-Hytec Cover & Traction Bars
    NGK Iridium Tips & MSD Ignition Plug Wires Baja Spare Tire Holder 33x13.5 Hankook rt03 18" XD Rims
    Innovate LC-1 Wideband o2 Sensor x2 HID's all around LED taillights and 3rd brake light
    BDS Dual Steering Stabilizers Pioneer Double-DIN Touchscreen Navigation with Two 10" Subs under rear seat
    Electric Fan Autometer Pressure, Boost, and Pyro Gauges
    4.56 Gears Airlift Air Bag Suspension

  2. #2


    My only thought would be a loose chain if it does it an 4 hi and 4 low. Did it do this before with the old trans?

    2004 SILVERADO 2500HD LS
    Pro Comp Leveling Kit
    285-75-16 Cooper ST All Terrains
    Pro Comp Programmer
    Bilstein Shocks
    Linux Bed Liner
    Tinted Windows

    Other rides:

    1967 Landcruiser <350 Chevy>
    1970 Camaro
    1990 Geo Metro Convertible
    2007 FJ Cruiser

  3. #3


    I never got to use the transfer case with the old transmission, it blew on the second time driving it. I have a couple ideas, U-joints, front driveshaft splines, or the loose chain.

  4. #4


    Chain may even be broken, I broke 2 in my old Dodge and it displayed the same symptom each time.

  5. #5


    Changed the fluid in the transfer case and didn't have any metal in it, so i think it's stretched.

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