Leaf shims after 3103-CV hack-n-tap

[kootenayXJ]

Sorry to beat a dead horse but I've searched and unfortunately, the more I read, the more confused I get. Please try to be patient as I ask some (probably) stupid questions and try to regain some sanity!

I just finished doing a 3103-CV hack-n-tap SYE on my 2000 XJ sport, 3" lift, 5spd with 8.25 rear end. The entire thing went really well and I used a front driveshaft from an '89 Dodge Dakota as it is longer than the usual junkyard donor (XJ front shaft) that most people use. My measurements worked out perfectly and the slip yoke on the donor shaft sits in the middle of its travel allowing plenty of room under compression and extension.

My only problem, is of course that I need to install shims under the leafs to tilt the pinion up and be 2-3 degrees under the driveshaft angle.

I'm a bit confused regarding which shims to use now - I'm certain that I've measured the driveshaft angle and pinion angle correctly, and the numbers I get show a 10 degree difference between the two. Subtract 2 degrees for the pinion to rise under power and this leaves me with an 8 degree difference to make up with shims.

Most people say they use a 3 degree shim for this height of lift after a SYE but it's looking like I will need around 8 degrees. This seems way off to me. Can someone verify this please, am I missing something?

Here's a photo I found on - in my case, the difference between the two yellow lines is 10 degrees.

 

[kootenayXJ]

oops double post

 

[ehall]

The driveshaft angle will also change as the pinion pulls up the end.

I am using 6 degree shims on my RE 4.5" lift, and it works pretty well

 

[md21722]

4 degrees is pretty normal for a 3" lift. Are you using extended shackles or what not that could be pushing your pinion down? Past 6-8 degrees you would be looking at cutting off and welding back on the spring perches.

 

[Euology101]

Can you post photos of you measuring angles, might be that your measuring in a place that may not be precise, if your finding that you need 10*.

Everyone here can tell you what they did on their jeep, but at the end of the day, every set up is different.

Also, tell us your plans for the rear suspension. For instance if you plan on doing a shackle lift, that will make a difference to your pinion angle, as already mentioned, and we may be able to help you not spend $$ two times.

Edit: when I had 3.5" lift, stock shackles, I had 6* shim and that put me within 2-3* of good, sitting still. Under load at 70mph vib free.

 

[Euology101]

4 degrees is pretty normal for a 3" lift. Are you using extended shackles or what not that could be pushing your pinion down? Past 6-8 degrees you would be looking at cutting off and welding back on the spring perches.

Extended shackles would push your pinion up, as will lift version relocation brackets.

 

[kootenayXJ]

The driveshaft angle will also change as the pinion pulls up the end.

ah, this was something I hadn't considered and makes perfect sense now. Anyone have an idea of what kind of ratio I would expect? 1:1 roughly? If so that would explain why most use a 3 degree shim for this height lift. My maths are...far from up to this kind of problem.

Can you post photos of you measuring angles, might be that your measuring in a place that may not be precise, if your finding that you need 10*.

Also, tell us your plans for the rear suspension. For instance if you plan on doing a shackle lift, that will make a difference to your pinion angle, as already mentioned, and we may be able to help you not spend $$ two times.

I'm measuring the slope of the driveshaft by placing the anglefinder on the base of the driveshaft, then I used a socket in the bottom of the u-joint cap and the anglefinder resting against that to get the pinion angle. This is how I've seen it measured online and seems like it would give me an accurate reading but maybe I'm mistaken.

No plans for the jeep in the future, the measured lift is 3" over stock with the stock shackles and will probably stay at this height for many years to come.

 

[Euology101]

Another thing you should consider is the leaf springs that were used. The center hole location could be different than "stock" or another set of leafs, putting the axle at a different angle. Again, everyone's set up is different, you can't expect to see 3" of lift = 3-4* of shim for everyone. As I mentioned before, I had 3.5" lift springs (ome), with stock everything else, and found I needed 6* shims. This put me 2-3* under parallel meaning I was out about 8-9*. Under load (axle wrap) brought it up to "parallel" and essentially corrected for that 2-3* , which is why everyone says you want to be slightly under.

Personally, I bet if you put a set of 6* in, you'd probably be good.