Silverado Big Block Owners(8.1 liter)

Discussion in 'Trucks and Trailers' started by mckell68, Jun 6, 2003.

  1. mckell68

    mckell68 LawnSite Member
    Posts: 46

    Thinking about a silverado 2500 HD with the 8.1 liter. Is this a monster or what? What kind of realistic gas mileage can you get out of it? Any problems or complaints on thus motor? All comments appreciated----Mike
  2. pottstim

    pottstim LawnSite Senior Member
    Posts: 501

    I'm sure you can find some good opinions on that truck and engine here, but you can probably find out more at
    I frequent that forum quite a bit, and from what I hear most guys with the 8.1 get around 12 mpg or so unloaded. If memory serves me right, I think I remember someone saying they got nearly 15mpg, which is great for that size engine. From what everyone says, this powertrain is a heck of a puller. If you decide to visit that site, post your question in the GM truck forum. You will have to register for the forum, but it is quick easy and free just like Best of luck.
  3. bluebeard

    bluebeard LawnSite Member
    from ny
    Posts: 21

    9mpg loaded or unloaded, headwind or tailwind.
  4. CO.d 502nd

    CO.d 502nd Banned
    Posts: 288

    When i was still in partnership with my brothers we had the big block ,its a beast allright haul a mountain but look to get po mileage at best.Dang good motor though.
  5. Jimbo

    Jimbo LawnSite Bronze Member
    Posts: 1,093

    Bluebeard is right. With an engine that size she doesnt know if you have a loaded trailer behind you or not- gas milage is near the same regardless. Is that a gas engine? If so you might want to go diesel for a motor that size.
    Damn near twice as big as the engine in my rig.
  6. TLS

    TLS LawnSite Fanatic
    Posts: 7,937

    Great engine. Not quite sure they needed to stretch it to 8.1 Liters though. That extra 42ci, while I'm sure is nice, probably isn't needed if they were to simply tweak a few things on the old 454.

    I really am not a big fan of the new Allison or its pricetag. I really AM a fan of the new Duramax, however between the Allison and the Duramax, I can buy a brand new Lazer! WAY too much of an upcharge for an engine/transmission option IMO. If I'm going to pay THAT much for a Diesel option, it better be a HO Cummins under the hood!

    Ideal combo would be the 8.1 and the 4L80E (they offer it in the Suburban). I'd buy one in a second as its only an $800 option.

    If I were you I'd look at what the 6.0/4L80E is capable of. And if it will meet your needs. It's no slouch, but if your going to be towing heavy every day (large enclosed trailer, etc) it may not be for you. You really need to wind the 6.0 up a bit to get it to work.

    If your buying a BIG BLOCK truck, fuel mileage should NOT be on your shopping list! People have been asking me my Big Block mileage since 1989! Best was 12 worst was 5.
  7. o-so-n-so

    o-so-n-so LawnSite Bronze Member
    from Alabama
    Posts: 1,218

    I own an 2002 2500HD 4X4, 8.1, Allison Auto. Upgraded from a 2000 Z71, Auto OD, 5.4 (327)

    I am very pleased with my truck. Plenty of motor to compliment the Allison Auto. Tran is electronically controlled to shift when needed and also will downshift going downhill to save your brakes. I bought as a work horse. No carpet, vinyl seat, A/C, and a radio is about it. Paid $29 something interest free money. 8.5 mpg working and 9.8 mpg not working.

    No regrets on the upgrade............good luck.

  8. ACER

    ACER LawnSite Member
    Posts: 89

    I have a 2002 GMC 2500HD, 8.1 Litre 5 speed Allison with 3.73 gears. Running unloaded I get around 12 mph. Have not checked the mileage loaded. Does appear the gage moves to empty a lot quicker when loaded
  9. wxmn6

    wxmn6 LawnSite Member
    Posts: 163

    Actually the 4L80E is standard for the 8.1L engine. You have the option to upgrade to Allison for extra $$. You can get 4L80E with 8.1L on 2500HD and 3500. :cool:
  10. pottstim

    pottstim LawnSite Senior Member
    Posts: 501

    That is incorrect. When you get the 8.1 in the 2500 HD or 3500, you must get the Allison auto or the ZF 6 spd. The 4L80-E is available in the 2500HD and 3500 dooley with the 6.0 only. If you opt for the manual trans with the 6.0, you get the NV 4500 5 spd. Now, if you want a big block 8.1 in a Suburban 2500 or the Avalanche 2500, you get the beefed up version of the 4L80-E, which is called the 4L85-E. The reason behind this is because the Allison is too tall to fit in the 'Burb or Avalanche. If you get a chance sometime, compare the frame height of a 2500HD to a Suburban 2500. You will see the frame rails are much taller in the truck as opposed to the Suburban. That is why the Allison won't fit in the 'Burb. Hope this helps.


Share This Page