TF 999/998 sporting internal diff from the 904 ?

Discussion in 'Transmission and Drivetrain Tech' started by rustytoolss, Nov 8, 2018.

  1. rustytoolss

    rustytoolss Well-Known Member

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    First question. Does anyone know what the first year was that the 999//998 was used in production vehicles ?
    Since there does not seam to be any tell tale signs of which trans you are looking at 904/998/999 externally.
    How can you tell if you've got a 999/998 and not at 904 internally ?
    I know the 999/998 have lower gearset. But if you do not know how to spot the 999/998, tell me what to look for ?
     
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    • Mopar69gts

      Mopar69gts Member

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      There should be a model / ser. number
      On the drivers side just above the oil pan.
      Call a dodge parts dept. With that number they can tell you what it is.
      That's what I did from a 1987 d100 truck it's a 998.
       
    • VOETOM

      VOETOM Well-Known Member

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      You can make some really slick smaller Torqueflites out of 998 and 999s.
       
      Last edited: Nov 8, 2018
    • 408 swinger

      408 swinger FABO Gold Member FABO Gold Member

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      I think all the 998/999 were lock up transmissions. So a quick tell tale sign would be look at the input shaft. There will be a short, unsplined portion on the very end it.
       
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      • AJ/FormS

        AJ/FormS 367 FormS clone 3.09-1.92-1.40-1.09-.78od 3.55s

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        A-998s Were not ALL loc-ups. On the top of the bellhouse behind the Distributor, you should find cast into the bellhouse , the call-outs A998 or A999
        I have one each A-998 non-loc-up, and A999 loc-up. They are wide ratio transmissions and work well with super-high hiway gears, behind stock hi-torque low-rpm engines, and adapt well to slightly juiced up SBMs . But for big-cams, you still need to keep pace with compression and upgraded rear gears and or a higher Stall TC, same-old/same-old. For streeters I recommend to concentrate on what second gear is doing.
        The ratios are 2.74-1.54-1.00,and splits are .56-.65;(versus 2.45-1.45-1.00 and splits of .59-.69 in the regular A904).
        With 3.55s this makes your roadgears 9.73-5.47-3.55....... so the stock 112LSA cams work well. That 5.47 road-gear will get you about 60@4400, kindof a good place to be with a stock 318.
        EDIT; I think someone once told me that not ALL A998s had the wide ratio gearset, so buyer beware. Mine does
        Also, with a 2800TC, your 318 will haul the mail with this combo; and you can forget about up-camming it.
         
        Last edited: Nov 8, 2018
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