I want to move the rear axle rearward 1-2" for a number of reasons. Handling, stability, better clearance to the front of the wheelwell for 35" tires.
Any advice or tips or what to watch out for?

How much can the axle be moved rearward before the diff cover hits the gas tank or JCR skid plate?

How far can the axle be moved rearward before the driveshaft comes undone? Using SLE and DS for 4" lift.

Looking at relocation blocks to move 1-1.5" and 1/2' lift.

Looking at longer springs with pin bolt moved further back. Front runners are Durango springs 56" and pin is 1" back and use shackle relocation box and move the shackle bolt to the last most rearward hole.

Or Blazer springs 54" and pin is 1.5" further back.

Any thoughts or ideas?

 

Gas tank clearance will greatly depend on your diff cover and skid plate. Your drive shaft will be the same deal, I have no idea how long your shaft is (no homo) so I can't tell you. What I can tell you is that you're going to want stiffer springs or a ladder bar. My buddy's is stretched ~4" and he's got insane axle wrap. I think his is a set of RE packs that have been flipped though. Your shocks will need relocated and the exhaust may need modified as well. The only experience u have with a stretched XJ is one that has been stretched a lot further than you plan on so take it for what it is.

 

I looked into stretching mine about an inch. The best solution would be to weld on new spring perches.

That's the best because of you tried to redrill the stock perch then the center pin on the leaf spring would be almost on the edge of the perch, and it's the same deal if you use those relocators blocks.

You probably use those relocators blocks and be alright, it's just not the best option. I would avoid redrilling or flipping the springs or using super long leafs.

I'm not sure about clearances in your situation. That's something you'll have to determine yourself. I will say that a stock front driveshaft in the rear will get maxed out quick.

 

I did a 2" stretch with spring perches and my D60 diff cover clears my rusty's skid by about an inch.

 

stock XJ----51.5" (23"/28.5") 4 leaf, 1.125", 5.5"arch, 745lbs
Comanche--57" (26"/ 31") 4 leaf, 1.50", 10.25"arch, 1280lbs
'96 Blazer---52" (24.5"/27.5") 4 leaf, 1.625", 7.25"arch, 1400lbs VCF221013
'99-'04 Dakota-56" (24/32) 5 leaf, 1.4625", 7"arch, 1200lbs
'98-'03 Durango-56" (24/32) 3 leaf, 1.625", ?arch, 1800lbs
Rubicon Express #1461=5.5"lift, #1462=4.5"lift, #1462=5.5"lift

sdtrucksprings.com

 

Move the gas tank into the cargo area, comp cut the fenders, and flip the leaf springs around and run the shackles off a rear bumper tied in properly. Pretty pointless to move it back an inch or two because the shape of the wheel well is going to seriously interfere if not eliminate up travel.

 

Sorry, didn't want to do all that. So if 6" is better, then 2" is good?

I have Notch flares on one XJ and Napiers on the other. I want to keep it street legal and near stock looking but 'max it out' as much as possible.
The idea is to push the long arms forward about 1" and the rear back about 1.5-2".
The response I want is 'Is that a stock XJ, something looks different, I can't tell'. Not 'Oh yeah that's an XJ with 1 tons and comp cut'.

Is running the gas tank in the cargo area legal? In PA we have inspection and emission ****'s.

 

Look where your tire sits in the wheel well. You move it back 2" and all it's going to do is go directly into the body when it travels up. Your flares don't matter. The only way you're going to fix that is to cut the rear wheel well past the pinch welds and you're going to need to redo them at that point anyway and your flares will no longer fit. It's not like the front where there's just a bolt on fender and you can trim it out to accommodate.

You could get away with it on an MJ if you ran a flat bed, but a 1-2" stretch on an XJ is pretty pointless.

As for legality I'm going to go out on a limb and guess it wouldn't be legal since PA is about the worst state in the country for vehicle equipment laws.

 

I moved mine back because with longer shackles it moved my axle forward so moving the axle back 2" put me back just a bit less than dead center of the wheel well. When it compresses the tire sits dead center instead of hitting the front of the wheel well.

 

This is all I was looking to do with moving my axle back