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Opinions/Experiences with GMC Diesel

Discussion in 'Chevy Trucks' started by tvpierce, Dec 8, 2006.

  1. tvpierce

    tvpierce Senior Member
    from Maine
    Messages: 209

    I'm considering purchasing a '96 GMC 1-Ton with a 6.5 liter turbo diesel and automatic transmission.

    What have been poeple's experiences with this engine? Or this engine/tranny combination? (in terms of durability, longevity, etc.)

    Thanks in advance for sharing your insight.

  2. Oshkosh

    Oshkosh PlowSite.com Addict
    Messages: 1,655

  3. Bruce'sEx

    Bruce'sEx Senior Member
    Messages: 873

    We have two GMC 3/4 ton with the 6.5 tur

    a 93 and a 99, and both are great trucks, nothing really bad to say, we haul up to 3 tons behind both of them all summer long. and both plow.

    our 93 has gone through two trannies I think now, and the one in it is getting do, I can feel it. Think it was the reverse both times.
    the 99 we picke up two years ago, and so far not a single problem (touch wood).

    Cold nights use the block heater. or they don't want to start.
    We only use gm oil filters by the recommedation of our mechanic, and other that have diesels.
    other then that I can't think of much unless you have specfic questions.
    Last edited: Dec 8, 2006
  4. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    pre 97s are prone to overheating and blowing the passenger side head gasket. Doesn't have to happen if you watch the temp and don't try to kill it, but a better option is to upgrade to a 97 cooling kit which gives you two thermostats and reroutes the coolant to both heads. Old system cools left head first then right head gets hot coolant. A good exhaust to get rid of the incredibly restrictive factory system will wake it up and give you a couple more mpgs as well. I bought the Banks Stinger kit because it came with downpipe and gauges, but there are several suppliers out there. The trans is a 4l80e, decent tranny, mine has over 150k with no trouble, I tow an 11k camper, push a Blizzard 810 and now have a little sander. I have had some problems with my truck, replaced the glow plug control module that wasn't turning on the glow plugs, replaced the oil cooler lines because they always leak at the stupid crimp. I also replaced the oil cooler at the same time because I snapped it when I was unhooking the cooler lines. PMD was done last year. People will tell you the 6.5s are known for injector pumps, but that is not true, what fails is the Pump Mounted Driver, which is a little electronic device mounted to the pump. Best thing is to get a replacement PMD, a cooler plate and extension harness and put the new one on the fenderwell away from that intake valley heat. Don't even bother taking the old one out, just unplug it and leave it there, it's nearly impossble to get at the bolts. If you do buy it and you're interested I can take some pics of my mods and send them to you, along with some sources for parts. Keep the fuel filter changed every other oil change (I do oil and filter every 5k on the 5 thousands, and fuel filter every other time) There's a few other things I've learned, don't have room here for it. Overall I've been really happy with my truck, it's not the powerhouse that a Duramax, Cummins HO or Powerstroke is, but it's not $40 grand either. For what it is it is a pretty respectable motor.
  5. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    There are two GMC 6.5 4x4s for sale near me, both for $3850 and both show 320-330k on the odometer. I wouldn't expect much more than that out of them. It shows they are good for 300k miles, but who knows how much longer than that it will go. I wouldn't buy one with that many miles, that's when you start getting nickel and dimed to death.
  6. Bruce'sEx

    Bruce'sEx Senior Member
    Messages: 873

    Sounds like you have had alot more trouble then we have with are trucks, mind you we don't put much milleage on them, but what they do put on them is all work.
  7. Dragonscapes

    Dragonscapes Junior Member
    Messages: 17

    The 94 I had did over 500k on the original drivetrain then the engine went they can be great trucks but when they break.... Injection pumps are a known problme on them just be sure that it has the 4L80E on it and not the 4L60E for some reason if the tranny's been repaired or replaced they sometimes end up with the light duty one and they generally don't hold up to heavy work
  8. tvpierce

    tvpierce Senior Member
    from Maine
    Messages: 209

    Thanks for the responses.

    DetroitDan, thanks for the heads-up on the cooling issue. If we get this truck, I'll definately take you up on your offer for further info.

    I didn't/don't have more specific questions... you folks gave me exactly what I was looking for. My limited knowledge of GM diesels goes back to the early 80s, when their reputation was less than stellar.

    It sounds like by the 90's, GM got things sorted out. Would that be an accurate statement?

    Thanks again.

    Jeff Pierce
  9. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    I'd agree on your diesel assessment. The old converted Oldsmobile 350s were garbage, the 6.2 non turbos were gutless, so the 6.5 turbo was a big improvement. They improved upon it gradually over the years, unfortunately they switched to the Duramax just before the whole hotrod diesel craze took hold, so there is limited aftermarket performance available for the 6.5. The 6.5 doesn't compare power-wise to a new diesel, but for what it is it's a darn good motor. Everyone loves the Cummins because of the huge aftermarket, but stock they weren't as powerful as the 6.5 was back in the 90s.
  10. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    If you do any reading up on the old 6.2, you will find it was meant to be a fuel-miser diesel, not a powerhouse. It was designed to be an alternative to a 305 gasser, but with twice the fuel mileage. Modern diesels cannot touch the old 6.2 for MPG's. Well into the 20's....

    The 6.5's were harder on fuel because people wanted more 'oomph'.

    One of my favorite links on the GM diesels is:

  11. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    havent read that in a long time. Makes me want to rebuild my truck to those specs. Probably be a lot cheaper than doing a Cummins conversion. Every time I think about giving my old truck the boot and getting something newer, something like that comes along and makes me want to keep mine. It seems like a lot of money, but compared to what buying a newer truck would cost, I could completely restore the body on my truck, rebuild the engine with the intercooler and other mods, and still spend less than ten grand. Can't replace the truck for that. I wonder what kind of numbers that truck was putting up? I bet it was approaching 300 horse.
  12. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    just found a company selling them on ebay, everything but the intercooler for $7200. Ouch!