The ECU is the computer under the dash as you described. From all the data the various sensors provide, it determins the spark timing and fuel timing (and amount)and controls the steppermotor and if present the EGR solenoid.

No sites about axle wrap this quick, but do a search on the SWB. XJ's don't seem to suffer from axle wrap a lot. No idea exactely why. Axle wrap is the pinion angle going up or ddown under load, cousing vibrations and even binding on the U-joints. I think CJ's suffer from it because of the short shafts and V8 blocks. Not sure.

 

You sorta got it right NIX, but not quite, axle wrap is really a missnomer, it is really called SPRING wrap, basically if you could look at the leaf springs from the side of the jeep (with out the wheel in the way, so you'll just have to imagine it in your head instead) while someone else hammered the gas from a dead start, you would see that the leaf springs will want to twist into an s shape, another way to put it would be to say the wheels want to rotate counter clockwise (looking at drivers rear wheel) and the axle housing (demonstrating Newtons 3rd law of motion) want's to rotate the other direction, and since it is attached to the leaf springs it causes them to twist.
This situation is less prevalent in a cherokee because it has shorter leaf springs but don't fool yourself, it does still occur and can be a serious source of destroyed drive train parts especially on lifted cherokees.

 

so should i worry more about addressing it with a comanche because the springs are longer? an article i read addressed it with some sort of stabalizer.. i guess ill just have to wait and see

 

Build it, wheel it, make it better if necessary.

Basically, i wouldnt worry a ton about axle wrap right now. Once its done, you will know if you have bad axle wrap that needs to be addressed. If you do, then its time to start searching over on the dark side (PBB) for designs on anti-wrap bars or ladder bars, or whatever their callin em these days.

-jm

 

I would say build up, and if you expierence a problem start looking into traction bars, the kind that mount above the spring or axle set up.

 

It seems that you could cure axle wrap with a cheap set of lakewood traction bars in front of the axle.

 

I'm confused

Is axle wrap something new or are y'all talking about axle/spring warp? Not trying to be an a$$ but are these two seperate things?

 

All of you are right. I was a bit short in my answer. On these Jeep boards it's mostly called axle wrap (but it's not the axle itself). During acceleration the pinion wants to point upwards as the rear wheels turn forward. This warpes the leaves into a kind of S-shape. It's not the wrap itself, but the alignment of the driveline that's problematic. There's lots of bars to prevent wrap. Some above the axle restrict articulation, some under the axle restrict ground play. Not knowing YJ's or CJ's leaf length or MJ's I'd prevent axle wrap by making sure the leaves are firm enough not to wrap. I know not to make the ride to stiff. Lifting with blocks is 1 of the main causes of axle wrap, because of the stronger moment on the leaves. I think a lift with a short AAL is more prone to cause wrap then using long AAL's. Not speaking from experience, however....

 

thanks for the info NIX. i was already thinking about taking my very very sagging RE 3.5" AALs and put them in the MJ (for stiffening only, probably wont lift much because of the length differences), maybe another leaf from my old XJ packs as well (since i have the dakota springs to put under there). The RE AAL sags a fair amount. im not too concerned with the ride anyhow, the RE coils i got in my XJ are stiff as a corpse. im 235lbs and i can bounce on the front bumper with very little compression of the coils. im used to a rough ride.

A funny little anecdote though...

I drive my XJ pretty hard on the road.. usually dont slow down for dips/bumps in the road.. i may even speed up! Well, in December i left my house at about 10 PM, got down to the road (i have a 500ft gravel driveway) and i heard my fan hitting on the shroud, so i got out to check it out, and right as i open the hood, the fan hit the shroud even more and shattered it... something didnt look quite right. so i just parked it and was goign to check it out in the day light.

well the next morning my brother wakes me up at 6am because its my turn (ughhh) to take him to work at my familys restaurant. In my stupor from having about 2 hours of sleep, i forgot what happened with my car last night, and we both just hopped right in and went on our way.

About 3 miles from my house, there is this high pitched whine coming from the powertrain, so i immediately slow down and start to pull over. after about 3 seconds of this whine.. "BANG". im still rolling, and my driveshaft is binding really bad and making the rear end hop. the engine is still running, im thinking "man what went wrong?"

I look underneath.. the driveshaft, t-case and transmission are all at very odd angles. pop the hood.. the engine is crooked in there, sloped to the passenger side. that evening after we remove the driveshafts, my dad tows me home with his truck.

We had thought the motormount broke.. but the bolts from the motormount bracket to the block ALL (3) sheared off on the passenger side.. the fan was about 1/16th inch from my week old radiator.. close call... im extremely greatful that this didnt happen on the highway, could have been a LOT worse than it was. Now i check all my nuts and bolts every couple weeks!