1. #1
    GaryMB's Avatar
    GaryMB is offline Senior Member
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    Oct 2004
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    tj jerking around

    I have a 1984 cj7 with a 258, dana 300, and t5 transmission. The jeep has about 180,000 miles on it, and I'm getting into pretty serious offroading. Instead of rebuilding the stock 258 and t5, i would like to move up to something with more power and durability. For engines, I'm considering: 258 with 4.0L head and 4.0L fuel injection, stock 4.0L, and 4.0L stroked to 4.5L with the 258 crank. For trannies, I would like either a 4 or 5 speed manual that will work with the d300; I'm considering an ax15 and t18A but am not familiar with all the trannies available. I'll be doing all the work myself, and would like to keep the price down. Of course, compromises have to be made, and I don't know enough about engine/transmission swaps to make a good decision. I do need enough power to climb steep grades with a well equiped (i.e. heavy) cj7, and need a transmission that can handle this power offroad and go on the freeway. What would you recommend?

  2. #2
    Junkpile's Avatar
    Junkpile is offline Senior Member
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    RE: Newest, Youngest Jeeper, Its a Girl!!

    Any of those engines would make fine powerplants for a Jeep that sees hard use. VERY durable, and the power isn't too shabby either. I'd probably suggest the stroker, with an otherwise factory rebuild. A small conservative "RV" type camshaft would help too. If you ever want more power from that point, you can go a long ways with those inline sixes, and with that broad torque curve they are preferable to a V8 in 90% of offroad driving. An inline 6 cylinder generally produces 30% more torque than a similarly sized V8, with a similar setup, and it does it over a broader rpm range.

    For transmissions, look no further than the T-176 4 speed that was available from the factory under your Jeep. If that box won't fill your need.....start looking for adapters to mate another brand transmission to your engine. The T-18 is a very good box if you want granny low, but they never came with D300s so an adapter is needed there too. Please don't put an Aisin/Warner transmission in front of a built AMC I6......you might as well leave the T5 in it if you're planning on doing that. They are both grenades, and the pin is just itching to fall out every time you press the gas pedal. Just an idea, if your open to them that is......an automatic works WONDERFULLY behind an I6. It won't be a rocket, but an auto with a factory(or close to it) torque converter does a great job of using all of that bottom end torque that the long stroke provides.
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