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Can't get into 4WD after changing front differential

Discussion in 'Wrangler TJ (1996-2006)' started by jeepinmissouri, Jan 5, 2017.

  1. Jan 5, 2017 at 2:42 PM
    #1
    jeepinmissouri

    jeepinmissouri [OP] New Member

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    First Name:
    brian
    Vehicle:
    1998 TJ
    I have a 1998 Jeep Wrangler Sport and I am having the front differential replaced because of a bad pinion. The front diff (dana 30) is marked as 4.10 and the rear (dana 35) is a 3.73 with trac loc. I am now having trouble getting into 4WD and the mechanic is saying it is because the gear ratios don't match but it came from the factory that way so why now won't it work??
     
  2. Jan 5, 2017 at 5:17 PM
    #2
    chris4x4

    chris4x4 With sufficient thrust, pigs fly just fine Moderator

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    Welcome! If the gear ratios are different, its going to cause issues.
     
    Bob likes this.
  3. Jan 5, 2017 at 7:17 PM
    #3
    OFFGRID

    OFFGRID Well-Known Member

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    First Name:
    Peter
    Houston
    Vehicle:
    1979 Jeep CJ7, 258, TH350, NP208
    Howell fuel injection, header, HEI distributor, TH350, NP208, SOA lift with YJ springs in the front & GW springs in the Rear. AMC20 with G2 1 piece chromos trussed, Dana 30 with G2 chromos and 760x ujoints and MM Stainless Hubs, Geared 4.56. Tom Woods shafts, Metal cloaks, Caged, 37" Toyo MTs.
    Did you buy this jeep new? Sounds like someone swapped in another axle. 373 generally came with the 6cyl and the 410 came with the 4cyl. This is probably why your pinion is messed up. The 410 pinion is smaller than 373 and therefore weaker.

    My next question is are you reading these numbers on the ring gear? If you are only replacing the front you need to install a 373 ring and pinion. You can get a factory used R&P on eBay for under $100.

    http://www.ebay.com/itm/DANA-30-3-7...ash=item1a22971161:g:HuwAAOSwzaJX49kd&vxp=mtr

    Good luck.
     
    Bob likes this.
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