Need More Power

[mattgrant11]

I have an 89 MJ with a 4.0 and auto tranny, I am currently building it for mud runs, I have 34" ltb's right now, during the mud runs I run it in 4lo and 1st gear but it shifts up to second anyway, when it shifts into second it doesn't have the power to turn the tires and by the time it shifts back to first I have lost all my momentum. Somebody told me to look into a manual valve body for the tranny but so far I can't find anything that would fit the comanche, does anybody know of a manual valve body for the comanche's or have any tips on how to get more power out of it. This is going to be a temporary fix due to the fact that this winter I will be putting a 305 in it so the cheaper the better

[bigd44889]

gears gears and more gears

power don't mean much

the best thing is all gears

305 don't have the torx that 4.0 does

[BLHTAZ]

Definitley, upgrading the gears is the way to go. Running 4lo and first gear is not the right way to do mud either, that could be part of your problem. You should be in 4hi to get the tire speed up, as 4lo will not turn them fast enough for mud running. 4lo and first gear would be for slowly crawling up rocks :thumbsup:

[Automan2164]

Running stock gears with 34" meats? :ack: That's might be half the battle there. I would at least go to 4.10's. You most likely have 3.55's now. I would go for a 4.7L stroker before the 305. More oomph.

 

Rob L.

[mvusse]

Doesn't Don have like 300hp at the wheels with a 4.7 stroker and some other add-ons? You'd be hard pressed to get that out of a 305 for the same money. If you really do want to put a sbc in there, why not a 383? For mud bogs you need hp, and lots of them. I suggest whatever you do, make sure it is built to handle nitrous. That's the cheapest power adder if the engine can take it.

[TrailReadyMJ]

I agree with the gears... but as a band aid...

You can also put in a switch to keep it from shifting into 2nd when in the 1-2 position.

Just gain access to the TCU behind the passenger side dash. There is a YELLOW wire with a 10A inline fuse in it. If you install a switch on that wire to take power off the TCU (or remove the fuse), it becomes a "manual valve body". Just keep in mind you don't have any 2nd gear option when the power is off.

You can however wire in another switch to choose between 1st and 2nd manually. To do this, you need to tap into the #1 solenoid (Dark Blue/White wire in TCU harness). By applying power to this wire (you can get power from the vehicle side of the Yellow wire mentioned above.), it will shift into 2nd gear when in the 1-2 position.

Make sure you don't use the 1-2 switch when normally driving in 3rd or OD positions or unwanted gear changes will occur.

Hope this helps :)

[HOrnbrod]

Doesn't Don have like 300hp at the wheels with a 4.7 stroker and some other add-ons? You'd be hard pressed to get that out of a 305 for the same money. If you really do want to put a sbc in there, why not a 383? For mud bogs you need hp, and lots of them. I suggest whatever you do, make sure it is built to handle nitrous. That's the cheapest power adder if the engine can take it.

 

Not quite. :D It's a 4.6 stroker and at the last dyno run w. the new 99+ curved intake and tuned Unichip was 261.1 HP @ 4400 RPM, with torque at 312.8. Peak torque was 345 @ 3500 RPM. W/o the 25%-30% power loss of the AW4 peak HP would be well over 300.

[mvusse]

Still that's about 50% more than the stock Renix 4.0's 173-177hp.