few questions about building an XJ properly

When it comes to tech, I'm a newbie plain and simple. Read the "for newbies" websites posted on here but didn't really get any questions answered. I've had my 1998 XJ Classic for a little over 6 years now. I had a 2" budget lift on it and did some wheeling around NC, WY, and KS (which is where I'm from and live now). About 10 months ago I put a 6 1/2" IronRock Offroad long arm kit on with some 35x12.50 Maxxis Bighorns. Onto the questions:

Do I really need a SYE, the lift came w/a drop kit and IronRock says I don't need one. If I do, how do I measure for it and the CV? (Haven't heard any vibe while driving)

Can anyone tell me about what backspacing I need with my tires? I'm running on a 15x12 aluminum wheel but want to go steel here soon. My tires rub on the backside of fender well pretty bad.

My Jeep makes kind of a slight clunk noise when I let off the accelerator at higher speeds (50-60mph), anyone else ever experience this?

Like I said, not very tech experienced but joined this forum to learn . Any help would be greatly appreciated. Also, anyone around the Ark City, KS area let me know. Would definitely like to get together and wheel around.

1) Slip yoke emiminator: If you have no vibes and you're happy with your ground clearance with the trans drop then leave it. Otherwise most measurements are measured yoke-surface to yoke-surface, your driveshaft manufacturer will let you know what measurements they prefer and help walk you through it. Some places will want to know the measurement for resting and fully drooped so they know how long to make your slip joint.

2) Backspacing: You'll want a narrower rim. 12" is rather wide for a 12.5" wide tire. try an 8" or even a 10" wide rim with 4.5-3.75 backspacing - this is a guess, i'm sure someone else will chime in with a little better estimate for you.

3) Clunk: Start by checking the condition of your engine and trans mounts.

Thanks a lot soopergoober. yea i kinda figured 12.5" was a little too big, but got the wheels and tires for free from a buddy, all I had to do was put a lift on his XJ for him. I'll check out those mounts and make sure they are good.

You dont want 10" rims either,8" w/ 3.75"BS will get you where you need to be!

RCP Phx said:

You dont want 10" rims either,8" w/ 3.75"BS will get you where you need to be!

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Thanks for the correction RCP Phx.

Definitely check your engine and trans mounts.

With your late model you may need to lubricate the spline shaft, do a search, plenty of threads on it.

Awesome...thanks again for the help everyone.

also on the clunk, you may want to check your U-joints on the driveshafts.