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1990 Suburban 2500 to keep or not to keep?

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by 90Batwagon, Jan 3, 2010.

  1. 90Batwagon

    90Batwagon New Member

    Hi , I'm new to this forum. I have a 90 V2500 that I have basically made new. Crate motor, new 14 bolt FF rear, a/c , paint, the norm. The big problem is mpg! I get about 10-11 it has 3.73 rear and a th400 trans. I know the trans is the main problem with the mpg. It you put the truck in neutral it flies down a hill put it in gear and you don't need the brakes. I have access to an 88 suburban with a th700r and though about converting it to that tranny but wasn't sure if my mpg will go up. Or selling it and getting newer one. If any one has any suggestions that would be great! I have alot of money in this truck but the mpg stinks. Thanks for your help!
  2. omnisi

    omnisi Rockstar 100 Posts

    I love our '90 model. If I already had that much $$ in it, and you like it, just do a tranny swap to the 700R4 with OD....of course driving style is a factor. OD wont help any in town.


    Or, even easier yet, do what I do when I have a big 4x4 truck dont check the mpg, put gas in it, and have fun. Yours sounds nice...pics??
  3. DAREDEVIL

    DAREDEVIL Rockstar 4 Years 1000 Posts




    :great::sign0017::sign0011:
  4. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Unfortunately the trans is only part of the MPG problem.
    A 700R4 swap will help mileage but this is a big, heavy, aerodynamically challenged truck that'll never get great mileage.
    Everyones idea of good mileage is different, this truck converted to a 700R4 with a tune-up and driven with a light foot could return 14/15 mpg on the highway, I've heard as high as 18/19 highway driving.
    I say keep it and convert, you obviously like this truck, you've already spent a decent amount of $ to upgrade and make it reliable.
  5. Willie G

    Willie G New Member

    Hmmmm....10 mpg versus 30 mpg with gas at $2.50/gal. At 2000 miles per month, that's 200 gallons ($500) versus about 70 gallons ($175) - You save $325.

    But if the new vehicle only gets 20 mpg, your savings drop to $250.

    But then you have to add in the difference in what the new vehicle costs - if you buy used, figure a year or more to break even.

    If you buy new, then it could be 4-6 years to the break-even point.

    None of this counts the higher insurance premiums on a newer, more expensive vehicle.

    If you don't drive 2000 miles per month, it takes even longer to pay off.

    It's your choice, just make sure you run the numbers first - lots to consider.
  6. 90Batwagon

    90Batwagon New Member

    Thanks for the input! I'll try and get some pictures up. I know the truck will never be the greatest on fuel. I would be happy with 15 mpg. The motor only has 12,000 miles on it with no crazy upgrades. I thought about putting an overdrive add on by Gear Vender but that's another $2600 just for the product not counting the trans rebuild. Switching trans is where I'm steering , but I'm not sure if I should have the drive shaft cut b/c the 700r is longer or trying to find the conversion for the U joints. I heard that the 1/2 ton U joint is different then the 3/4. My other thought is trying to change the ratio in the Th400 with a rebuilt but don't know if that will truly work? My final is getting a 92 burb 4x4(131,000 miles on it, 1/2 ton) and swooping motors. Thanks again. Its nice to see I'm not the only one out there that loves these trucks !
  7. 90Batwagon

    90Batwagon New Member

    Here are some pictures. It needs a 4 inch lift!

    Attached Files:

  8. DAREDEVIL

    DAREDEVIL Rockstar 4 Years 1000 Posts


    Cool, but i asume its the white one ???:lol:
  9. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    If you lift it and put on bigger tires theres goes the MPG again.
    The 700R4 with the transfer case is longer I believe than your TH400, I'd get a driveshaft out of a donor later model truck so you dont have to do any cutting. You'll still need the Spicer adaptor U-joints for the rear axle since you have a 2500.
  10. Willie G

    Willie G New Member

    My 90 R2500 is geared the same - TH400 and 3.73's. The difference is the 454 under my hood.


    But I still get 10-12 mpg.


    You can do the 700 swap, but I'll bet you don't see more than 1-2 mpg increase, if any. As noted above - it's a really big, heavy shoebox pushing through the wind.


    Just enjoy..... :great:

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