question about shims

I have been talking to a 4x4 shop about installing my lift for me. I don't have the tools to do this myself. They are telling me that "Unfortunately you cannot shim the rear enough degrees with shims. To run a cv shaft correctly it needs to be at 1 degree below 0 at the rear differential compared to the shaft or you will experience pre-mature u-joint failure and possibly a vibe." Is this true? They want to cut off the spring perches and re-weld them. By the way I have a 2001 Cherokee and I'm installing a RE6030 3.5 inch lift with the Hack-and-Tap and the RE driveshaft. Can a shim be used or are they correct in saying that I have to re-weld the perches?

Not true. You can use shims and/or a longer rear shackle to acheive the correct angle. The correct angle will have to be determined by measuring after you get the lift installed. Wait until the springs have settled in before making the correction. Adding some weight to the rear of your XJ while you break in the springs will speed up the process. It shouldn't take but a day or two that way. You can take also it out and flex the suspension to break in the springs. I've got a 4.5" lift and only needed to use longer shackles. I'm using shackles from a Chevy pickup. They are 1.5" longer than stock.

Semper Fi said:

I have been talking to a 4x4 shop about installing my lift for me. I don't have the tools to do this myself. They are telling me that "Unfortunately you cannot shim the rear enough degrees with shims. To run a cv shaft correctly it needs to be at 1 degree below 0 at the rear differential compared to the shaft or you will experience pre-mature u-joint failure and possibly a vibe." Is this true? They want to cut off the spring perches and re-weld them. By the way I have a 2001 Cherokee and I'm installing a RE6030 3.5 inch lift with the Hack-and-Tap and the RE driveshaft. Can a shim be used or are they correct in saying that I have to re-weld the perches?

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Go to the shop and tell them they are full of crap. I have 2.5* shims in the back of my '99 and I'm at 6" of lift with an SYE. I think they are just trying to hustle you for some more money and time. Now don't get me wrong, cutting and rewelding the spring perches is the correct way to do it, but with 3.5"? give me a break, you might need 1.5 degree shims if that. My guess is that with an SYE and 3.5", you'll probably be right at 1-2* below the center of the output shaft which is right on, so you might not even need shims. Tell the shop to go eat a big one.

that shop is crazy. i have a 5" lift running a TC drop (np242) and 6* shims. never had any vibes even after the lift was first installed and sat at 7" for a day or two.

-Tim

If that kit uses a TC drop , I think it does, cutting and rotating may eliminate the need for the drop. As previously said cut and turn is the way when you can. Steel shims are also available up to 6*. G'luck, Mike.......<can't spell

I have a TC drop on it now but I'm removing it and replacing it with the SYE. I have a 3 inch lift on it but I'm also replacing that with the RE 6030. Should I have the lift put on, drive it for a while and then decide if I want the axle shimmed or the perches moved?

Semper Fi said:

I have a TC drop on it now but I'm removing it and replacing it with the SYE. I have a 3 inch lift on it but I'm also replacing that with the RE 6030. Should I have the lift put on, drive it for a while and then decide if I want the axle shimmed or the perches moved?

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I would get it put on and see where it sets. Then get the springs to settle a bit and check it again.

With the money you are paying them to put that on you could go get yourself a small set of tools and do it yourself. Putting a lift on is one of the easiest things you can do on an XJ. Good jack stands are a must though. I used a set of those tin things the first time I did mine. Was quite interesting.

The hieght is what you need. These are the Harbor Freight stuff but I've seen them all over for about the same price. I have a set of Jet's and the Harbor junk and I almost like the Harbors better.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=38847

I've used a bottle jack to do a lift before but even a small 2 ton floor jack it much easier.

Get a friend to help you. They don't need to know any more than you but an extra set of hands is very helpful.

I think the thing that scares me the most is the centering of the front axle. I put on the 3 inch lift that is on it now and that was a piece of cake, well not quite I broke 2 ratchets and it took 11 hours but I did it. The Hack and Tap I will not try to do myself because all I have is simple handtools and nothing to cut the shaft with.

Centering side to side or cross ways? Both are pretty simple. I've always had good luck adjusting the track bar but having it loose, then bouncing it with the wheels pointed straight, then adjusting the trackbar to fit that length.

For the control arm lengths I generally use the rear axle as a guide. Have everthing in place and then check the distance from the rear axle to the front. Adjust the lengths to fit. I also try and find some a common spot on each side and check from there also.

Do you already have the Hack and Tap? I always recommend Tom woods because you end up paying the do it yourself price and he cuts the shaft.

Using too small of ratchet. Also if you had to deal with any rust issues it shouldn't be as bad this time because you've had most things already off. I would put anti sieze on any bolts that are trying to rust.

the centering from side to side is what has me worried.

Semper Fi said:

the centering from side to side is what has me worried.

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When I replaced my stock track bar with an RE 1600 at about 3.5 inches of lift I just bounced the jeep up and down a few times and then adjusted the bar to fit. It will pretty much align itself. No prob!

I am currently sitting at about 5.5 inches of lift. Roughly 4 from springs (dakota pack) and 1.5 from shackles. I didn't need a shim to get the angles correct. All jeeps are different. Mine didn't need shims. Yours might need 3* only way to find out is to do it and measure.

Good luck