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  1. #1

    Default Neglected rear end diff, same as neglected tranny?

    I can't remember the last time I changed my rear diff fluid - bad, I know. The good news is, I don't tow and rarely haul with my truck. In fact, I don't even have a towing package. Therefore, my rear diff has never really been stressed so hopefully the fluid isn't "bad". The only thing is, I really think it's been close to 100,000 miles since I last changed it. So, my question is this: will it hurt to change it out since it's been that long or should I leave it be? It's a well known fact that if you haven't changed out your transmission fluid in a very long time, it's actually better to leave it at that point or the transmission will fail if you change out the fluid. Considering my siutation, will the same thing happen to my rear diff if I change out the fluid after it's been so long?
    Clint (TX) 2001 Silverado LS 4.8L auto 2wd ECSB [GARAGE]
    Gasoline or gunpowder: If you ain't burning one, you ain't having fun!
    NRA Endowment Member 5 24 48 88 - Hendrick Motorsports FTW!

  2. #2

    Default

    No the diff is a little different it'll appreciate the fluid change.
    Since you dont change it as often you might think about using synthetics back there.

  3. #3

    Default

    Quote Originally Posted by tbplus10 View Post
    Since you dont change it as often you might think about using synthetics back there.
    Definitely a consideration but a new question arises: they say it is bad to switch over to synthetic oil in your engine after years of using regular oil. Again, does the same rule apply to the rear diff or no?
    Clint (TX) 2001 Silverado LS 4.8L auto 2wd ECSB [GARAGE]
    Gasoline or gunpowder: If you ain't burning one, you ain't having fun!
    NRA Endowment Member 5 24 48 88 - Hendrick Motorsports FTW!

  4. #4
    Sr. Engineer
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    Oct 2010
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    Default

    Who is "they" that you get your info from? I personaly think it is never to late to change your fluid and if it fails sometime after that it is due to the fact that it was failing anyway and only convenient to blame it on something other than your own neglect.
    2000 GMC YUKON SLT, 5.3L tow pkg, G80 rear/w 3.73 gear

  5. #5

    Default

    I get my info from auto parts stores, general repair shops, transmission shops, etc. You know, the experts/professionals.
    Clint (TX) 2001 Silverado LS 4.8L auto 2wd ECSB [GARAGE]
    Gasoline or gunpowder: If you ain't burning one, you ain't having fun!
    NRA Endowment Member 5 24 48 88 - Hendrick Motorsports FTW!

  6. #6

    Default

    The big issue changing to synthetics is increased chance for leaks, all synthetics do is let you know yes I have a leak and now that I know I've gotta do something about the problem.
    Synthetics create less drag and friction one reason for this is they permeate metal and gaskets better than conventional oils, this is why after starting to use synthetics you suddenly find you have a leak, it was there all along it just wasnt as obvious.
    Look at your axle seals and, pinion seal and rear cover gasket, if they need replacing nows a good time, if their in bad shape they will start leaking anyways, might be a week after you change the fluids or it might be a year, either way they need to be changed.

  7. #7

    Default

    Quote Originally Posted by tbplus10 View Post
    The big issue changing to synthetics is increased chance for leaks, all synthetics do is let you know yes I have a leak and now that I know I've gotta do something about the problem.
    Synthetics create less drag and friction one reason for this is they permeate metal and gaskets better than conventional oils, this is why after starting to use synthetics you suddenly find you have a leak, it was there all along it just wasnt as obvious.
    Look at your axle seals and, pinion seal and rear cover gasket, if they need replacing nows a good time, if their in bad shape they will start leaking anyways, might be a week after you change the fluids or it might be a year, either way they need to be changed.
    Thanks for the info TB. I'll more than likely have a shop change the rear diff fluid so while it's in there I'll have them replace all the seals/gaskets and then fill it with synthetic.
    Clint (TX) 2001 Silverado LS 4.8L auto 2wd ECSB [GARAGE]
    Gasoline or gunpowder: If you ain't burning one, you ain't having fun!
    NRA Endowment Member 5 24 48 88 - Hendrick Motorsports FTW!

  8. #8

    Default

    Oil is an organic compound so in time, heat and age will break down gear oil. Ever change out an old one and, noticed the rancid smell? Believe me, your gearbox will appreciate it!

    - - - Updated - - -

    You are right about the synthetics! I was running royal purple and the dealer put mobile one in, now I seem to have a rear seal leak!! 30,000 on the truck, and I know royal purple is synthetic also but I've had the same experience with Mobile 1 before.

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