‘15 JKR on 37s w 3.5” b.s. on stock axles and 3” synergy lift. I want to do a stretch so I don’t feel like I’m going to tip over backwards as easily when doing steep climbs. A little more stability off camber would be nice as well. I am happy with my height and up travel. I don’t want to mess with the gas tank and will be staying on stock axles. I may move up to 38s at the most.
Since I’m not going to mess with the tank I am assuming that I have to stick with the stock arm configuration? Is there any reason that I should modify, reinforce or move the stock control arm mounts?
My primary concern is steep climbs and I don’t know if I should go conventional coils, coil overs, or ORIs?

 

Best stretch is to buy a JKU . Seriously though to do this right will be a lot of money. You need an axle relocation kit and the best way is with a long arm kit even though you said you did not want to screw with the tank. Will ride nice with that though so that is a benefit. Drive shaft lengths would have to be changed as well, brake lines and even wheel sensors depending on the extreme you go to. Lastly the body at the rear will have to be modified.

 

The factory frame mounts are good enough but your geometry will suffer some from using them. I would stay away from stretch kits, they are too compromised geometry wise. I would also stay away from a 3" or 6" stretch as the benefits are really seen when you can get that rear wheel just past the rear bumper. If you are mainly just crawling then I would go with the ORI's as they are a more simple set up not need limit straps, sway bars, bump stops, and coils but you need to be willing to mess with them to get them tuned right and you will need to have a bottle of nitrogen for adjustments. If you are anal and don't like seeing your jeep leaning on the trail then you might not like ORI struts. If you like going fast off road then coil overs or conventional coils with bypass shocks. Standard coils may be a pain to relocate the upper coil mounts. You also have to decide where you want to mount the shocks. If you outboard them you really are going to need wider axles or you will be cutting a lot of the tub and frenching the frame. Wider axles will also add a lot more stability off road when you add the longer wheel base.

Stretching is a lot of work and expense and I would not half ass it. The fuel cell is an issue but not really that hard to do. It's mainly "where do I put it" and typically takes up all the room in a 2 door. But it does open up the the underside so you have room to do some nice suspension work. Also realize that stretching basically ruins the resale vale of the jeep so I would to do it unless it is something you plan on keeping forever.

Good luck with your project.

 

Why would I have to change wheel speed sensors?

What specifically are the drawbacks of using stock arm mounts? Why is a dt 4 link so amazing? I’m not aiming for more than 12” of travel. Can ORIs be set up properly on a stock rear axle?

 

You don't have to change wheel speed sensors but may have to lengthen the wires, no big deal. The DT is better mainly due to getting rid of the track bar and ridding the axle shift during articulation. That and you put the frame mounts where they should be to give a better ride and work better with your pinion angles during articulation. An ORI should be set up for a 50/50 up down at ride height and should be able to set up depending on where you plan on mounting them, tire size, and how much trimming you plan to do. An ORI is roughly the same as a 2.0 coil over in terms of fitting and are best when mounted near vertical (top in) on top of the axle.

The stock arm mounts are located where they are for the stock suspension. They are made for short arms and create pinion rotation during articulation. They have to work around the fuel tank. They work with the factory axle control arm mounts which are IMO poorly placed and hang down way too much. Raising the lower axle mounts on a custom long arm requires you to raise the upper mounts so you get proper separation for tire size. Changing those mounts and not the frame side creates poor geometry and very low anti squat numbers. The low anti squat numbers transfers the weight shift when accelerating into the coils causing a lot of squat and when you brake the weight transfers to the front causing the rear coils to unload (loss of traction) and the rear end jumps up. You will also likely experience more body roll and be more unstable under off camber situations.

 

So the upper axle side control arm mounts must be moved up the same as the lower if trying to gain clearance? Does the frame side as well? So the separation must stay the same?

Whats your opinion of the Full Traction CRC?

 

As a general rule you want 25% of the tire height in link separation so 37" tires would be around 9.25" from upper to lower on the axle side. The frame side will not have as much and you want to try and have the uppers and lowers links converge around the water pump on the motor. This throws the weight transfer into the links and chassis more than the coils so less squat.

The watts link is ok, I never really cared for it as it is complicated and just another maintenance item to worry about as well as adding weight. TheWatts link will steal up travel as well. I think it requires around 4" of lift to be usable. A good balanced set up will have nearly equal amounts or up and down travel.

 

So am I a right assuming that it’s not worth the effort to modify the stock mounts to gain a little bit of clearance?
The evo long arm mounts look great for clearance but seem like they would bind.
How are ORIs on the street?

 

It depends on the what you want in the end product for your effort and expense. ORI's are find on the street once you get them dialed in. Like anything set up makes the difference.

 

Thanks for all your help