GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 4 of 4
  1. #1

    Default differential ratio

    I have a 1990 gmc sierra 4x4 ,Ive owned it a couple of years and afert having the transmission and transfercase rebuilt I just put it in 4wd the other day for the first time and realized my front and rear differential are different and the rear is pushing the front I need to find out the front end ratio for that model since changing threar would be easier than the front

  2. #2

    Default

    Welcome to the club, it's good to have you aboard. If you post this in the tech portion of the site you may get your answer quicker. Good luck.


    2002 Chevrolet Silverado Extended Cab SportSide: See Mods in My Garage

  3. #3

    Default

    Moved to powertrain forum.

    If it's apparent that someone has changed one of the gears, then I would think the only way to be sure of the front gear ratio is to actually count it out, unless you have some good service records for the truck. Sure, you could check the RPO code in the glove box, but there is likely no way to know if that is still what is in the front end of the truck.

    To measure the gear ratio, jack up at both front wheels and at least one rear wheel. Put the transfer case in 4H and the transmission in N (with the stock thermoelectric center axle disconnect CAD, you will probably have to have the key on for this test, to make sure the CAD is engaged). Rotate that front tires through one rotation (make sure both tires turn together) while counting the number of rotations of the front driveshaft. The number of rotations of the front driveshaft is your gear ratio (about 3.5 rotations means 3.55 gear ratio).
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  4. #4

    Default

    Reading @MrShorty 's answer, has me thinking; if you jacked up all four, marked the bottom of each tire, and started the engine, placed the trans into a forward gear and let the wheels turn a couple of times. you could be sure the gear ratios are different if the tire marks are no longer together (say, both are not at 3 o'clock).

    Note, you could do this with only one side in the air if you are sure the rear is not posi/locking
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

Similar Threads

  1. Trying to get gear ratio
    By renchr01 in forum Chevy Silverado Forum (GMC Sierra)
    Replies: 11
    Last: 01-24-2011, 02:09 PM
  2. What is my ratio?
    By kcfocus1 in forum GM Powertrain
    Replies: 1
    Last: 09-14-2010, 09:05 AM
  3. Gear ratio
    By stringbender in forum General Chevy & GM Tech Questions
    Replies: 4
    Last: 02-08-2009, 05:49 PM
  4. Differential Ratio
    By CarpenterGuy in forum GM Powertrain
    Replies: 18
    Last: 09-22-2008, 06:16 PM
  5. Air to Fuel ratio
    By 94chevybowtie in forum Member Introductions
    Replies: 2
    Last: 09-11-2008, 05:38 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •