Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

GM Diesels Suck

bigfurbigfur Posts: 649
edited February 28 in GMC
I want to buy a new one ton diesel but my 3/4 GMC
deisel sucks. Any recomodatios. I have heard a
rumble here and there about a full CAT deisel in GM
truck. Someone please help me in my choice


  • queenmsqueenms Posts: 26

    I have heard those rumbles from GM fans for 2 years now. My father was an Operating Engineer on D-9 Cats all my childhood and I would consider buying a GM product if it were Cat powered. However I have been listening to the same rumors about the Cat powerplants in GM's for 2 years with no sign that it's about to come to pass.

    That is why I am going to go ahead with a purchase of the Ford '99 F-350 with the proven International/Navistar turbo diesel. Stump pulling power and a long life.

    If and when a Cat powerplant makes it into a light truck I will look at the brand it goes into.

    Does anyone else have more recent information on the Cat/GM rumours?
  • bigfurbigfur Posts: 649
    I actually work for GM, and alot of people in the higher up positions(trainer and teachers) have been mentioning the CAT. but if I don't hear more good news about it, Hello 99 F-350 xtended cab dually diesel.
  • mharde2mharde2 Posts: 278
    bigfur, Wow, you will be a big hit in the GM parking lot. I love it...
  • KCRam@EdmundsKCRam@Edmunds Mt. Arlington NJPosts: 3,495

    Maybe bigfur coming to work in a brand new Ford SD will let GM know that they couldn't make a suitable heavy duty truck... nothing lets a manufacturer know their products are weak like their employees buying the competition's products. Kinda like a Gateway employee bringing his Mac to work...

    KCRam - Pickups/Wagons/Vans+Minivans Moderator

  • bigfurbigfur Posts: 649
    Hey guys,
    I'm just like you. I like style and a whole s#$t laod of power. GM has the absolute weakest deisel on the market. I like working for them but I am not ever going to buy 6.5 deisel unless it was a deal i couldn't pass up(i havent come upon one yet).
    Thanks for the encouragement
  • fredwoodfredwood Posts: 79
    Is the GM diesel that bad?
  • bigfurbigfur Posts: 649
    I have heard and read(in town hall) many horror stories of GM deisels. There are people on their third or fourth engine by a hundred grand. Currently tey are experimenting with Isuzu and CAT engines, but havent heard anything beyond that.
  • KCRam@EdmundsKCRam@Edmunds Mt. Arlington NJPosts: 3,495

    The big knock on the GM diesels is lack of power. Until this past year, they hadn't even produced 400 lb-ft of torque WITH a turbo. Everyone is aware of the Dodge/Cummins and Ford/Navistar battle, and the heavy duty truck market shops there because they get power and good economy in a strong truck. The 6.5 needs aftermarket upgrades to match the power, and suffers in economy because you have to keep your foot in it more than the other diesels.

    Don't expect the next GM trucks to be successful even with the Isuzu diesels. You will hear "[non-permissible content removed] engine" almost immediately (as bad as that is to say), and the fear of expensive replacement parts (from the experiences with Japanese cars) will also drive people away.

    KCRam - Pickups/Wagons/Vans+Minivans Moderator

  • cdeancdean Posts: 1,110

    wait to you have to fix any diesel. its going to be expensive as hell whether it was produced in Japan, detroit, hawaii, whatever...

    GM diesels were designed at the lower horsepowers for effieciency reasons. i don't know how much yall know about them. the 6.5 turbo was a strong engine up till '94. it gave almost identical performance to ford's turbo 7.3 (pre powerstroke).

    My father bought a ton and a half chevy diesel in '94. that year, they change their injection system to completely computerized. there wasn't even a throttle cable, just a wire running from the accelerator to the fuel pump. the diesel was smokeless. you cannot make it smoke, no matter how hard you clutch it or put your foot into it. the engine met emission standards for year 2000 something.

    they had lots of software problems. my dads truck would die every now and then when he was slowing down to a stop and clutched it. not fun when your work truck weighs 14,000 empty. a GM engineer would come to the dealership with different stuff, because in '94, the really had no clue what was wrong with these engines. they tried several different computer chips. one of them they tried had awesome power. that motor would smoke like peace pipe, but would it run! they thought pumping up the fuel would keep the engine from dying. it did. but the chip also had a flaw that made injectors miss at idle, and the truck literally shook back and forth it was so bad (at idle).

    they finally found the software glitch and the truck has been flawless ever since. but it does not run like a powerstroke, and it gets only moderate mileage, but 12 mpg isn't bad in 14000#. another company with superduty powerstrokes in similar trucks never got better than 7 mpg.

    when a diesel smokes, there is more fuel burning than air will allow, or there is too much air. the black smoke you see is unburned fuel. the way GM did this is with an airgate. they carefully monitored the air fuel ratio at every instance, and would actually dump air out of the turbo line, if the mixture was not right. or the computer would cut back fuel, even if you had the accelerator pushed, that way--no smoke. the result: an engine that wouldn't go when you wanted to. basically that diesel grunt that everyone loves, happens you're at low rpms, you step into it, and some black smoke starts coming out the back as you accelerate.

    that was longer than i anticipated, but you basically have the story behind the 6.5 GM.
  • KCRam@EdmundsKCRam@Edmunds Mt. Arlington NJPosts: 3,495
    cdean - well-written post

    I really have to floor my Cummins to get smoke. It *does* have a cat-con, but the new 24 valve doesn't use one, not even in California.

    The 6.2 was so weak power and torque wise, and the 6.5 was viewed as a turbo "just to have a turbo". Until the "Powerstroke" version of the Navistar, no one could touch the low-end torque of the Cummins, and that spoiled a lot of people for what a diesel pickup should be. The 6.5 is finally over 200 horsepower; the Cummins and the Nav have been there for years, and the Nav has raised the torque benchmark to 500 lb-ft (which the Cummins will match when Dodge releases its 6 speed next winter).

    As you mentioned, the 6.2/6.5 was designed to be as gasoline-like as possible in terms of drivability, but GM has since learned, you need the strength as well.

    KCRam - Pickups/Wagons/Vans+Minivans Moderator

  • bigfurbigfur Posts: 649
    Has anyone got apprximate numbers on the Isuzu diedel engine.
  • cdeancdean Posts: 1,110
    i don't think there have been any kinda of release of any number. the '99 chevy's, all of them, will still get the improved version of the 6.5--440ftlb, 220 hp. i've heard a couple of owners with '97 chevy diesels saying they are much better and more driveable than the previous 3 years version. i wouldn't look for the isuzu before the '00 model.
  • DuckdogDuckdog Posts: 3
    What everyone need is a Ford with a Powerstroke and a Banks intercooler. You talk about power. And you should see the numbers over 600 foot pounds of torque
  • BrutusBrutus Posts: 1,113
    The new auto trans in the Superduty is only rated to 500 lb-ft of torque. I'm guessing you would kill your tranny if your engine generated 600 lb-ft of torque. From what I can tell, the tranny is the only thing stopping Ford and Dodge from putting the more powerful diesels in their trucks.
  • richflynnrichflynn Posts: 147
    Maybe I should have let this topic just die.

    I've been thinking of this almost since the topic was started. I'm also thinking back to the late '70s and early '80s.

    Perhaps the three key words are the topic title and that they are just plain fact.

    I dun-no,
  • fredwoodfredwood Posts: 79
    Just for grins, I pulled out my 1990 chevy brochure. The 1990 chevy 6.2 liter diesel pumped out a whopping 135 hp with 250 lbs of torque. Hmmm.
  • hcombs0hcombs0 Posts: 22
    Remember that 1990 was pre-Cummins and pre-Powerstroke (I believe). IMHO, had the Cummins not come along, I doubt diesel engines would not be at the levels of sophistication (factory turbos, 24V, electronic controls) that they are presently. Power levels would still probably be ~400ft-lbs and <200hp. As it is, it looks like the sky (or transmission capacity) is the limit.
    I'm not an apologist for GM diesels, but there is one in my garage. Taken as a whole package I like it and it's been reliable. It's not a Powerstroke, nor is it a Cummins, but I think 430 ft-lbs, 4.10 gears, and a 4L80 is enough to tow anything.
  • richflynnrichflynn Posts: 147

    You're partially correct about the Cummins forcing the competition to improve. The other half of the equation is the nasty four letter "S" word. The main reason for the electronic controls on my '99 PS is emissions!

    There is one thing rather interesting about the '99 diesel. The oil doesn't get junked up nearly as quickly as my old '92 7.3 L. I changed the oil in the '99 at about 2500 miles. It still looked like honey. In the '92 it would take about 1000 miles to turn black with carbon. Granted there are four more quarts, but still......

  • BrutusBrutus Posts: 1,113
    I think the first year for the Powerstroke may have been 1995. I went to the Ford Diesel Website and found the numbers for the pre-Powerstroke Ford diesel engines.

    1983-87: 6.9L, 170hp, 307 lb-ft
    1988-92: 7.3L, 185hp, 345 lb-ft
    1993: 7.3L, 185hp, 360 lb-ft
    1994: 7.3L(non-turbo), 190hp, 385 lb-ft
  • hcombs0hcombs0 Posts: 22
    That's interesting. It seems that Ford's non-turbo 7.3L was just as powerful in '94 as GM's 6.5L WITH a turbo. If the above figures are accurate, their output is identical: 190hp & 385lb-ft.

    A question to Ford guys: How much more power is in the Powerstroke? I seem to remember one poster mentioning 600ft-lbs. Obviously, there's more capacity in the Cummins engine.

    I ask because the GM 6.5 TD is basically tapped-out right now @ 430-440 lb-ft. As I understand it, the engine's comp. ratio is too high for more turbo pressure without detonation. So, GM's turning to Isuzu for their next diesel. Should be interesting.
This discussion has been closed.