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  1. #1

    Default Front Differential Question????

    I have a 1999 1500 Gmc sierra classic and I want to know what size the differential is in the front because I want to get a locker for it.

  2. #2


    Assuming your 1500 is a gasoline engine, you will almost certainly have a GM 8.25 inch IFS. To my knowledge, nobody makes a locker or limited slip for this differential. I'm afraid you, like me, are SOL until we figure out how to put a 9.25 IFS under there or a solid axle.
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  3. #3


    well can you put a Mini Spool in the front so it says locked all the time or will that mess up the diff

  4. #4


    You can do anything you want. To my knowledge, you won't find an aftermarket mini-spool to install, which would leave you with the option of welding up the spider gears.

    Remember that there are no hubs to unlock, so the axles and differential are always spinning, even in 2H. If you were to weld it up, you'd have issues with the steering all the time.

    But the real problem is that the 8.25 IFS is too weak to handle anything except an open diff (and there are some who don't think it is strong enough even then). I'm not sure what the weak link is -- probably axleshafts and/or the case, so you can weld it, but then you'll be spending your time on the trail breaking stuff. The point is that there are no good traction aid options for the 8.25 IFS.

  5. #5


    never weld the front diff unless it is a true off road rig like a rock crawler. u may be out of luck on this one because as shorty said the front IFS is pretty weak and is not meant to be wheeled hard. CV shafts are pretty weak and will break even with just 35s under decently hard off road driving. a mini spool up fornt will do the same and it will be very annoying to drive on road with the front permanently locked. i say dont even lock the front and put a good locker in the rear
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  6. #6


    I might just have to put a solid axle on my truck then

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