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4wd problem need help

Discussion in 'Chevy Trucks' started by ss502gmc, Jan 24, 2012.

  1. ss502gmc

    ss502gmc Senior Member
    Messages: 473

    The problem is with my truck in sig. So this past Friday we had a storm and roads were terrible so i put in fwd and something instantly felt like it was grinding. No idea what exactly so i stopped put in 2wd again and noise went away. So I stayed in 2wd until i started plowing because i was just spinning and only had about 1000lbs salt in bed which isnt enough to push snow in 2wd at some of my lots. So i put it in 4x4 and it works as it should but still makes that sound. So i noticed going 30mph down the road in 4x4 foot on the gas isnt to bad but as soon as i let foot off its horrible vibration. So today i crawled under to check front drive shaft u joints and all is well but then noticed the yoke in the front diff is sloppy in all directions up down side to side but no play while trying to turn the shaft. Also same sloppyness with the transfer case input an output shafts!!! Ive always used my 4x4 occasionally throughout the year hunting, plowing, pulling bushes out an things like that just to keep everything moving once in awhile so its not like im beating it but i need to figure this out and have no idea where to start and dont know anything about diffs or t-cases. But def need this fixed asap but dont have the $$$$ to throw away to go thru the process of elimination. Im mechaniclly inclined but have never touched these tupe of things before and dont have a garage. Any help is appreciated thanks guys!
     
  2. USMCMP5811

    USMCMP5811 Senior Member
    Messages: 267

    Sounds like your front diff is coming apart. there should be no play in the pinion. Possablly the pinion nut has backed off causing your pinon bearing to go south.
     
  3. ss502gmc

    ss502gmc Senior Member
    Messages: 473

    Do you know what is involved to change out the bearing?
     
  4. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    What year is your truck?? Easiest thing to do is call a junk yard and get a whole front diff from there and pop her in. Replacement parts for those front diffs are big $$. Friend of mine that had the same problem as you got a junk yard complete replacement for $300. Or I mean if you have the $$ to rebuild your current one then go for it as it'll be brand new but another friend of mine that is a mechanic at a big chevy dealership has an 04 2500HD with the front diff gone in it...his price for a rebuild parts only was around $1k...he's going the junk yard route!
     
  5. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    What year/model truck?
     
  6. ss502gmc

    ss502gmc Senior Member
    Messages: 473

    Its a 01 2500HD 8.1 Allison. The mechanic I use for the big jobs told me I should go the junk yard route also. He crawled under it and saw the slop in it himself and said its more than likely the pinion bearing and that he couldnt give me a price till he tore it apart and priced out parts and labor. And told me I could prob swap out the diff myself in 4 hours. He gave me a ball park estimate of $800-$1000. Im looking into a newer cc dually dmax and dont want invest that kinda $$$ into it.
     
  7. ss502gmc

    ss502gmc Senior Member
    Messages: 473

    The other question I have is if i go with a junkyard replacement how can I tell if its got the right gearing? My truck has 4:10's where most others are 3:73's. I cant imagine front diffs are that easy to come by but also dont wanna get the wrong gearing. Not 1 junk yard in my area has ever had a 01 2500hd or any of the nbs for that matter any time ive gone there for stupid little stuff like license plate lights or a mirror switch.
     
  8. USMCMP5811

    USMCMP5811 Senior Member
    Messages: 267

    Pull the diff cover. on the ring gear there will be a set of numbers. it will look something like this:

    14 - 10 - 41 - 9 - 83

    The first # is the axel type

    the second number is the # of teeth on the pinion gear

    the third number is the # of teeth on the ring gear

    the fourth and fifth number is the date of manufacture

    the above number will translate to this

    14 = GM Corprate 14 bolt axel

    10 = pinion gear teeth

    41 = ring gear teeth

    9 - 83 = manufactured Sept 1983


    Now take the number of ring gear teeth, and divide by the number of pinion teeth

    41/10 = 4:10 to 1 gear ratio


    if the second number was 11, then the ration would be 3:73 to 1 Thumbs Up
     
  9. ss502gmc

    ss502gmc Senior Member
    Messages: 473

    Ok, thanks for the info! Looks like ill be shopping for front diffs now.
     
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Fast easy way is to look at the RPO list in the glove compartment of the donor truck. GT4 equals 3.73 and GT5 equals 4.10's. Most front diffs also have a paper tag affixed so you can double verify before final installation if it's still there. If it isn't, I recommend removing the diff actuator, locking the axle manually (throw a spacer in there and reinstall the actuator) and checking the ratio manually. Hold one axle stationary and turn the other exactly two full revolutions while counting the rotation of the pinion yoke. 3 3/4 turns of the pinion yoke nets you a 3.73 ratio and slightly more the four turns guarantee's 4.10's.

    Works on any open diff you need to know the ratio on. For a locker/limited slip diff simply turn the axle once instead of twice.
     
  11. you don't have a sig..........
     
  12. USMCMP5811

    USMCMP5811 Senior Member
    Messages: 267

    While this is one way to check, I still suggest pulling the cover for a few reasons. 1.) it verifies that someone hasn't changed the gear ration previousely and 2.) you can visualy inspect the new to you diff, doesn't have missing ring, pinion, and spider gear teeth.
     
  13. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    However there is no cover to pull. To visibly verify anything inside you split the cases.
     
  14. USMCMP5811

    USMCMP5811 Senior Member
    Messages: 267

    Brain fart. :blush2: I forgot chevy changed the front IFS designe prior to 2000.

    Just another reason why I love my SFA. Thumbs Up