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Loss of power

Discussion in 'CJ' started by Sambo, Mar 18, 2019.

  1. Mar 18, 2019 at 9:51 PM
    #1
    Sambo

    #1
    Sambo [OP] New Member

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    Sam
    Vehicle:
    1979 CJ7 4.2L auto w/ qtrac
    3" body lift, 2.5" suspension lift
    Hey folks noob here. Just got a 79 cj7 with I6 Auto. Does great just putting around but when i get out on the highway and start up a hill it just falls flat on its face. Doesnt seem to be downshifting or getting into the passing gear or maybe a timing advance issue? It has a vacuum advance but im not sure if thats the issue. Anybody else had this problem?
     
    Sambo, Mar 18, 2019
    #1
  2. Mar 19, 2019 at 5:33 AM
    #2
    aggrex

    #2
    aggrex Well-Known Member

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    DE
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    Tuffy>AEV>TTO>JW>STech>EVOcage>MagnaFlow>SpiderTrax>RockHard>TF>SpringTail>67design>Bolt>GPCA>Curt>
    Welcome @Sambo . Congrats on the new-to-you CJ7! With a nice 3" lift the previous owner may have added larger than original size tires to complete the look + capability. Larger diameter tires will alter the effective gear ratio with results similar to what you're experiencing. Plus being forty years old some regular maintenance may be in order as various systems can be a part of the problem. Share some pics of this vintage CJ7 via upload a file tab.
     
    aggrex, Mar 19, 2019
    #2
    JKBob 25 likes this.
  3. Mar 19, 2019 at 7:21 AM
    #3
    Prerunner1982

    #3
    Prerunner1982 Well-Known Member

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    Hello Sam, welcome from Oklahoma.
    Have you done a tune up on it? Cap/Rotor, plugs, wires, etc
     
    Prerunner1982, Mar 19, 2019
    #3
  4. Mar 19, 2019 at 6:52 PM
    #4
    JKBob 25

    #4
    JKBob 25 Well-Known Member

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    Welcome @Sambo. I was thinking the same as @aggrex and @Prerunner1982 . Awesome advice so far. Your in good hands there. But I am subbed. I like to learn new stuff. :D.
    I'm sorry your a noob o_O . Hope that works out for ya too? Lollloll.
     
    JKBob 25, Mar 19, 2019
    #4
  5. Mar 20, 2019 at 7:36 AM
    #5
    Sambo

    #5
    Sambo [OP] New Member

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    Vehicle:
    1979 CJ7 4.2L auto w/ qtrac
    3" body lift, 2.5" suspension lift
    Yep all new. Like i said, it starts great and runs great but every time i hit a hill on the highway its like im in too high of a gear and goes from 70 to about 45 and the amc th400 isnt dropping into second to help it back up or the theres an issue with the passing gear or timing advance. Idk I'll play with it some and get back to ya. Im new to cj7s and weak motors not motors in general. Lol
     
    Sambo, Mar 20, 2019
    #5
  6. Mar 20, 2019 at 2:23 PM
    #6
    Jim Beam

    #6
    Jim Beam Well-Known Member

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    It does sound like oversize tires with a stock gear ratio. As I recall the '79 CJ came with a 3.55 to 1 gear ratio. So, the larger tire sizes could be tough for hill climbs on the road, plus make it harder to stop the thing. The tranny can get overloaded also, check the fluid for any burnt smell.
     
    Jim Beam, Mar 20, 2019
    #6
    JKBob 25 and Sambo[OP] like this.
  7. Mar 20, 2019 at 2:25 PM
    #7
    Sambo

    #7
    Sambo [OP] New Member

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    1979 CJ7 4.2L auto w/ qtrac
    3" body lift, 2.5" suspension lift
    Will do for sure
     
    Sambo, Mar 20, 2019
    #7
  8. Feb 27, 2020 at 8:37 AM
    #8
    Cj5_fan

    #8
    Cj5_fan Member

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    Jeff
    Sedona, AZ
    Vehicle:
    1980 CJ5
    304 V8 Renegade with 4" lift, LSD front and rear, 3.73 pushing 33x12.5 duratracs.
    It is surely an impact of the tires and gear ratio that is causing the loss of power. I have the same issue - especially with the altitudue I live at, and the cheap ethanol gas which kills an addtional % of HP from a motor. That being said, your trans should kick down based on load and RPM. I had a wrangler that wouldnt kick down correctly and it was a simple adjustment at a transmission shop to adjust the kick down linkage correctly. Maybe that is all you need.
     
    Cj5_fan, Feb 27, 2020
    #8
  9. Feb 27, 2020 at 12:29 PM
    #9
    Jim Beam

    #9
    Jim Beam Well-Known Member

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    1986 CJ7
    Fuel Injection, Dana 44s, T18, 4.10s w/lockers
    Adding a tranny cooler can help with overheating issues which can destroy the tranny. Either that or putting an oem tire size back on.
     
    Jim Beam, Feb 27, 2020
    #9
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