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Thread: Speedometer bouncing

  1. #1
    Join Date
    Mar 2010
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    158

    Default Speedometer bouncing

    My 94 GMC K2500 Suburban the speedo is acting up . Its wont work right , or its bouncing all over the place and then sometimes it just stays on 0 mph
    Anyone have any ideas on where to start chasing this down ?

    Thanks Brian
    1994 GMC 2500 6.5LTD 4wd
    Marine injectors and built 4911 pump to run veggie oil

    1981 Toyota 22L Diesel Pickup

  2. #2
    Join Date
    Jan 2001
    Location
    Knoxville,Tennessee
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    2,639

    Default

    Check your plug going to the sending unit on transfer case. If it is good go ahead and pull sending unit to see if it is full of filings on the bottom end.

    Might check connections at VSB too. Pull glove box out and it will be a white plastic box about the size of a cigarette pack just left of the opening where the glove box was.
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
    -Patrick Henry


    A5150nut
    2006 K3500 D/A
    94 6.5 4x4 5spd Sold

  3. #3
    Join Date
    Dec 2000
    Location
    Hawaii/Arizona
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    259

    Default

    If it is cable driven remove the cable from the back of the speedometer. Put some wheel bearing grease on the tip of your finger and put it on the cable behind the speedometer and put it back on to the speedometer snug. If the cable is loose at the back of the speedometer it causes the needle to jump around. If it is electric check for a bad ground or bad sending unit.
    Good luck
    John
    *2006 Chevy, 3500, 4X4, DRW, (LBZ) D/A, CC, LT, 252K Miles, 19.5" Wheels, Mag Hytec Transmission Pan and Differential Cover, SS Grill Guard, Racor 2 micron aux fuel filter, 100 Gallon Aux Fuel Tank, using Edge Evolution, Predator Diablosport, Kennedy ECM tune, Fitch Fuel Catalyst.

    *2006 Four Winds, Dutchman, 36', RV, D/A, 5500 Kodiak.
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    BUY AMERICAN or CANADIAN, NOTHING from CHINA .

  4. #4
    Join Date
    Jan 2001
    Location
    Knoxville,Tennessee
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    Default

    Quote Originally Posted by CoyleJR View Post
    If it is cable driven remove the cable from the back of the speedometer. Put some wheel bearing grease on the tip of your finger and put it on the cable behind the speedometer and put it back on to the speedometer snug. If the cable is loose at the back of the speedometer it causes the needle to jump around. If it is electric check for a bad ground or bad sending unit.
    Good luck
    John
    94 is electronic not cable driven.
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
    -Patrick Henry


    A5150nut
    2006 K3500 D/A
    94 6.5 4x4 5spd Sold

  5. #5
    Join Date
    Mar 2010
    Posts
    158

    Default

    ok thanks ill give that stuff a try this weekend ....
    1994 GMC 2500 6.5LTD 4wd
    Marine injectors and built 4911 pump to run veggie oil

    1981 Toyota 22L Diesel Pickup

  6. #6
    Join Date
    Sep 2001
    Location
    Lubbock TX, USA
    Posts
    4,194

    Default

    Sounds like speed sensor, wiring, or VSSB/DRAC Module behind glove box near the PCM.

    If you need a new VSSB you can get one at www.uniquediesel.com/drac

    Thanks,

    John
    1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
    1982 C10 SCSWB 6.2NA, 2.73 700
    1986 C10 SCLWB 6.2TD 3.73 700
    1989 V20 SUB 6.2NA, 3.73 400
    1994 G20 VAN 6.5NA, 3.42 60E
    1994 K20LD ECSWB 6.5TD, 3.42 80E
    1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
    1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
    1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
    1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
    1995 C20LD ECSWB 6.5TD 3.73 80E
    1995 K20LD SCLWB 6.5TD 3.73 80E
    1996 K30 DRW 6.5TD 4.10 80E
    1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway

  7. #7
    Join Date
    Dec 2000
    Location
    Walla Walla WA
    Posts
    69

    Default

    I had a similar issue. Turned out to be the male plug connector on the rear pickup. It was removed previously by someone who had the tranny replaced. Probably yanked on it to hard and broke one of the two arms. Was inserted but not tightly which led to sporadic speedo bouncing around.
    1994 K2500 ext cab. Recently repowered with; Non-cracked 599 block, factory compression, used old DSG girdle for main caps. Factory for what remains. Changed diffs to 3.42. Fuel economy Hwy 22.5 mpg US, in town without lcokup in 2nd/3rd - 18 mpg US.
    1994 K3500 CC LB Silverado. Next project. Built for endurance, power and gearing. Plan on opened up intake and exhaust sytem, best cooling mods, 4.11 gearing 4L80E, followed by Gear Vendors OD. Need to be able to split all gears and have lockup in 2nd/3rd/4th. Tan interior cloth, Bad ass dark blue (coming) aluminum wheels and air ride (coming)

  8. #8
    Join Date
    Mar 2010
    Posts
    158

    Default

    Ok ive cleaned the plugin on the transfer case and pulled it and cleaned the sensor . I will try the box int he dash next . Are these boxes the same on the gas trucks and burbs of the same body style ? if so i may goto my local pick n pull and get one . those new ones are pricey

    Thanks Brian
    1994 GMC 2500 6.5LTD 4wd
    Marine injectors and built 4911 pump to run veggie oil

    1981 Toyota 22L Diesel Pickup

  9. #9
    Join Date
    Jan 2001
    Location
    Knoxville,Tennessee
    Posts
    2,639

    Default

    Little white case just inside the dash. Pull glove box and its in the lip of the dash to your left. About the size of a cigarette pack.
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
    -Patrick Henry


    A5150nut
    2006 K3500 D/A
    94 6.5 4x4 5spd Sold

  10. #10
    Join Date
    Mar 2010
    Posts
    158

    Default

    Anyone know if the little white box on these are the same on the gasser trucks and burbs ? I took the one out of my 94 Chevy 1/2 ton with a 305 and I'm still getting the same thing . I may try taking the sensor back and get a warranty one and try that before i invest in a new box

    Thanks Brian
    1994 GMC 2500 6.5LTD 4wd
    Marine injectors and built 4911 pump to run veggie oil

    1981 Toyota 22L Diesel Pickup

  11. #11
    Join Date
    Jan 2001
    Location
    Knoxville,Tennessee
    Posts
    2,639

    Default

    Can't remember if it was bouncing or just quit all together on my 94. But it was filings built up on sending unit in transfer case where it reads the reluctor wheel. Just pull it out and see if its all covered in metal.
    "The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
    -Patrick Henry


    A5150nut
    2006 K3500 D/A
    94 6.5 4x4 5spd Sold

  12. #12
    Join Date
    Mar 2010
    Posts
    158

    Default

    I will have to try and pull it and clean it . I tried that when i first posted and it didnt seem to do any good . Ill clean it and if it dont help ill replace it
    1994 GMC 2500 6.5LTD 4wd
    Marine injectors and built 4911 pump to run veggie oil

    1981 Toyota 22L Diesel Pickup

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