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Thread: 6.5 turbo Diesel transmission help

  1. #1
    Join Date
    Dec 2018
    Location
    El Paso TX
    Posts
    2

    Default 6.5 turbo Diesel transmission help

    Hello guys,
    I recently purchased a 1997 GMC Suburban 2500 6.5 Turbo Diesel 4x4. Now I’m having transmission problems with the truck, seems to have a delayed and hard shift from 1st to 2nd and 3rd and won’t go into 4th od, tops at 40 mph. Any clues on what might be causing this and what to check first before trying to do a full rebuild. Hope to hear back from y’all, thanks! Truck has 86K miles

  2. #2
    Join Date
    Feb 2014
    Location
    NC
    Posts
    32

    Default

    How is the fluid level? Does the fluid smell burned?

  3. #3
    Join Date
    Dec 2018
    Location
    El Paso TX
    Posts
    2

    Unhappy

    No, fluid looks good doesn’t smell burned. But I’ll start there new fluid and maybe replace the filter.

  4. #4
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,575

    Arrow

    Welcome aboard!

    Step one: Replace the fuel filter.

    Then, verify the lift pump is running when it should, and is providing enough fuel pressure and volume. At idle, open the fuel water drain (Tee valve at the thermostat housing, routed to an appropriate container). The engine should continue to run while fuel fills the container.

    Is the SES lamp on?
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  5. #5
    Join Date
    Feb 2014
    Location
    NC
    Posts
    32

    Default

    Check the temperature sender on the drivers side head is plugged in.

  6. #6
    Join Date
    Apr 2001
    Location
    Newberg Oregon
    Posts
    12,292

    Default

    I agree with Maverick

    If there is an SES showing (Check engine lamp) pull the codes and see wasssssup..

    If no codes, then definitely replace the fuel filter and follow what Maverick said...

    A plugged fuel filter or failed lift pump can cause poor fuel flow and result in the low power.

    With the engine not producing power as it should you are mashing on the throttle harder and this tells the computer that the throttle pressure is high and this results in the hard shifts.

    The temp sender on the drivers side head is for the gauge only.. The sender on the water crossover up on the front of the engine is the temp sender to the computer...

    Keep us in the loop.
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2005 Suburban (Papa Smurf)
    THIS IS BOW TIE COUNTRY

  7. #7
    Join Date
    Dec 2003
    Location
    Yukon Canada
    Posts
    1,621

    Default

    Check your throttle position sensor.
    A friends sons 97 gasser was having tranny issues.He was going to replace but did some more digging online and discovered the issue.
    Replace the sensor and he is ratting the chyt out of it again.Been going for over a month now.
    90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews

  8. #8
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,575

    Arrow

    Quote Originally Posted by Yukon6.2 View Post
    Check your throttle position sensor.
    A friends sons 97 gasser was having tranny issues.He was going to replace but did some more digging online and discovered the issue.
    Replace the sensor and he is ratting the chyt out of it again.Been going for over a month now.
    It's a 1997 6.5 EFI Diesel. No TPS.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

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