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GM Diesels Suck

bigfurbigfur Member Posts: 649
edited February 2014 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 Member 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 Member 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 Member Posts: 278
    bigfur, Wow, you will be a big hit in the GM parking lot. I love it...
  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516

    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...
  • bigfurbigfur Member 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 Member Posts: 79
    Is the GM diesel that bad?
  • bigfurbigfur Member 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.
  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516

    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.
  • cdeancdean Member 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.
  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516
    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.
  • bigfurbigfur Member Posts: 649
    Has anyone got apprximate numbers on the Isuzu diedel engine.
  • cdeancdean Member 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 Member 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 Member 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 Member 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 Member 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 Member 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 Member 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 Member 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 Member 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.
  • stanfordstanford Member Posts: 606
    Of course, navistar produces several 7.3l "powerstroke" type engines with higher outputs, just as cummins does. Although I will admit that they don't scale as far (top of the line Cummins runs around 2,000 lb feet). It's all in the transmissions.
  • hcombs0hcombs0 Member Posts: 22
    Does anyone have any prediction as to where this power war will all end? Is it possible that we'll all be driving 600ft-lb diesels in 2002 or beyond?

    Also, why aren't diesel engine prices coming down? It seems to me that diesel engines are becoming more popular, and this should mean that manufacturers can spread-out costs more effectively, reducing unit price. However, the opposite is happening. Any ideas?
  • richflynnrichflynn Member Posts: 147
    The '99 PS 7.3L in my F-250 accelerates like a smaller gasoline (non V-10) engine would. Very impressive but not of much use at the stop light drag races.

    In comparison:
    The '99 PS 7.3L is rather quick and snappy;
    The '92 7.3L (non turbo) was acceptable;
    The '86 6.9L couldn't get out of it's own way;
    all three had a 3.73 rear end. Only the '86 was non LS.

    The '86 went through the Eisenhower tunnel on I70 at about 48-50 MPH while flat towing a Datsun 310 and carrying three adults with luggage. (For those of you who aren't aware, that's about 11,000 feet above sea level. A good example of torque too.) I was driving by the color of the exhaust. Clear, more throttle; black, less throttle.

    In all three trucks, I've never been happer with the drivability (Is there such a word?) of the diesel engines.
  • cdeancdean Member Posts: 1,110
    as power goes up on a diesel, so does the price. It is very expensive to get that kinda power into that displacement. those pre powerstroke 7.3's damn sure didn't cost $4500. innercoolers, turbos, hightech injectors, cost lots of money, lots! then, once you give yourself the ability to make all that power, you have to beef up the pistons, block, crank, rods, and cooling system, all so you can handle the power and dissipate the heat. diesel engine prices won't go anywhere but up. unless the engines get simpler. right now, diesel motors are the most complicated motors in trucks.
  • hcombs0hcombs0 Member Posts: 22
    That's sort of ironic, isn't it? A diesel being more complicated than its gas counterpart?
  • cdeancdean Member Posts: 1,110
    thats not ironic at all. i've worked on diesels since i was a kid. the simplest diesel is more complicated than the most complicated gas motor. Any average mechanic can go through an entire gas motor by himself. there are no complicated parts, nothing really special about them. newer motors with computers require you to have a code reader or some sort of software downloader. and thats it. the rest is like building a model airplane.

    There is no way an average mechanic can go through a diesel engine all by himself, even older ones, like 80's model engines. fuel pumps on diesels must be sent to specialty shops that have special tools and test equipment built specifically for diesels. those pumps have incredibly tight tolerances, small gaps, special screens (interior filters that are so fine, water cannot pass thru), and other intricacies. your cheapest rebuild of a simple fuel pump in the late 80's early 90's was in the $300 range.

    then there are injectors on diesels. there are only a few places in the country that actually work on injectors, and those are usually the producers. most of the time, you don't work on an injector; you buy a rebuilt set, and give yours to the dealer, and he sends them back to the factory in Timbuktu.

    turbos are extremely expensive, and are only worked on, built, or fixed in specialty shops. turbos spin at such incredibly high rpms, they have very specific bearing tolerances, and lubrication requirements, as well as high tech metals used for material, so they can withstand the heat.

    now, within the last 5 years, the diesels have become computerized. take all the crap i mentioned above, and throw in complicated fuel injection software that only a handful of engineers in the country actually understand. they only tell the servicemen how to fix it or reprogram it.

    if you thought buying a diesel is expensive, you better sit down when it comes time to fix it. everyone says diesels last longer than gas engines, but truth is, over a period of 200,000 miles, the only thing that you really have to replace (given good maintenance) is distributor, plugs, wires---ignition stuff. fuel pumps on these new computerized diesels today rarely make over 120k-150k at the most. that eats up about $1000. then you have injectors to go wrong, head gaskets more prone to blow. i can buy a lot of caps and rotors for that money.
  • hcombs0hcombs0 Member Posts: 22
    I hear you, especially about the fuel pumps. One of the reasons people hate the GM 6.5L is the problem GM had with electronic fuel pumps in 1994-1996.

    I was just saying how ironic it is that diesels these days are so complicated, since when they are conceptually simpler (no ignition system). I'm sorry if I touched a nerve.

    I know I'm asking lots of questions here, but diesels interest me a lot, not just practically (towing power) but conceptually (efficiency, special concerns). This conference has been a great help to me.
  • cdeancdean Member Posts: 1,110
    no prob, you didn't touch a nerve, i just didn't want anyone to think diesels were simple, because i mechanic-ed them for a long time, and know there is a lot to go wrong. you are right about the chevy '94-96 fuel pumps. they had probs with fuel pumps themselves and/or software. the trucks don't even have throttle cables, just a wire running from you foot pedal to the pump. technology is tops, but if it doesn't put out, then who cares. the chevy diesel has been maxed out as far as how much they get out of the current design, and it is about time they go somewhere to get a better one. they were competitve in the pre powerstroke era. engine power same as ford, just under dodge, and engines lasted. in '94, they got left behind.
  • glenn2glenn2 Member Posts: 39
    I guess the title says it all.....
  • bigfurbigfur Member Posts: 649
    NO S#$T
  • 0306199503061995 Member Posts: 1
    I think that all of ya"ll are makeink a big deal out of nothing be cause i drive one with deseal in it and it does every thing i need it to.
  • fredwoodfredwood Member Posts: 79
    The reason the chevy diesels are so disliked is that they really are an optional engine for the 350 not the 454. I can see why consumers would be pissed as spending a lot more money for an engine that does not provide as much or more hp and torque as the 454. I personally like the idea of a mid sized diesel engine (as long as its inexpensive). But the guys who need the power of a big block and want a diesel will be spending their money at the local dodge or ford dealer. Come on Chevy, get with it!
  • KCRamKCRam Mt. Arlington NJMember Posts: 3,516
    The GM/Isuzu diesel was announced today:


    6.6L V8 direct-injection turbo
This discussion has been closed.