6.5 Turbo Diesel: BIG trouble I think. HELP!

Discussion in 'Trucks and Trailers' started by MowJo, Dec 5, 2000.

  1. MowJo

    MowJo LawnSite Member
    from KY
    Messages: 70

    My 93' w/6.5 turbo diesel (automatic tranny-103,000 miles) downshifted from overdrive to 3rd on a broad sweeping curve and the engine noise suddenly became twice as loud as normal. I idled the truck off the road immediately (still running) to investigate the sound. It appeares to be coming from the top / center of the engine. When I firmly tap the accelerator the engine will die out. One more clue, when the truck is in park or neutral it sounds basically normal, put it in gear and the engine noise intensifies. It starts every time. Please advise, I am lost on this one.

    Thanks in advance
  2. TLS

    TLS LawnSite Fanatic
    Messages: 7,943

    Not sure as you haven't described your noise, but, I had a similar type noise when my flexplate cracked. No noise at idle, lots on acceleration. The diesel flexplates are really tough though so maybe its not the problem.
  3. MowJo

    MowJo LawnSite Member
    from KY
    Messages: 70

    I'll take any insight on this problem. I've been waiting 3 weeks for a diagnosis from the only reputable diesel guy in the area and am getting VERY AGITATED! The noise is basicaly the normal engine sound, only MUCH louder (there is no hole in the muffler: LOL). Could it be the turbo fan, breaking or has its bearing worn out? I think a big clue is that it dies out when you stomp the gas pedal as if there is an obstruction in the air intake choking it off. What is the flexplate and where is it?
    thanks again, MowJo
  4. Mudrtrukr79

    Mudrtrukr79 LawnSite Member
    Messages: 42

    I didnt realize GM used a flexplate in the HD.The last flexplate I saw was in my 72 Dodge Dart I had in High school. It had the same symptoms as your truck and the flex plate was bad in it. A flex plate is basically an X pattern steel plate that connects between your Motor and your torque converter in place of a flywheel

  5. mike reeh

    mike reeh LawnSite Member
    Messages: 229

    Not often you hear of a diesel not running well.. they seem so simple and bulletproof..

    also its news to me that they use flexplates in some autos.. thats very interesting.. what is the purpose exactly?

    mike reeh
  6. TLS

    TLS LawnSite Fanatic
    Messages: 7,943

    A flexplate is a 10 gauge (varies) sheetmetal flywheel with 168 teeth (varies) around the diameter. It links the crankshaft of the engine to the torque converter of the transmission. Flexplates are used in almost all vehicles with an automatic transmissions. The torque converter supplies plenty of inertia so a flywheel is not needed. They often crack in high stress areas causing a banging sound upon acceleration as the crack flexes side to side upon itself. The GM diesels have a thicker flexplate than gassers, but i would guess it is still possible for them to crack. They are relatively inexpensive, however, sliding back transmission and transfer case along with driveshafts is very time consuming.

    GM Diesels are far from simple and bulletproof. They have just as many sensors as a gasser, plus most garages dont have dedicated diesel "experts".


    Upon furthur reading of your post, it seems as though it may be the injection pump. This is the brains of your engine. The internal injection timing may have slipped and is causing it to run real bad. I would assume that you already replaced your fuel filter...right? Are you showing any codes?

    [Edited by dixie1 on 12-16-2000 at 12:53 AM]
  7. plowking35

    plowking35 LawnSite Bronze Member
    from S.E. CT
    Messages: 1,687

    The 93 was pre electronis injection, I believe it has the DB-2 mechanical pump. Go to the gm diesel page.

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