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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Everything is stock on the cherokee except the springs. 3.5 rubicon express. For what it’s worth have the same in coil springs up front but the front sits lower.
Let me toss this in here as I'm just not understanding your process (although there's a lot of things I don't understand). I put my angle indicator on the bolts of the case:
subtract that from the driveshaft:
You're looking for 1 to 3 degrees, I'm about a -1 (more that 3 may make it noisy or create too much wear, -0- will not allow the needle bearings to lubricate properly). "-" and "+" are relative, you want the angles such that the offsets cancel each other out, as shown in the image submitted above:
Also, I don't believe shim determination is a straightforward "subtract this from that and that's what you need for a shim". As you pivot the differential, you are also changing the driveshaft angle, so the "simple" calculation will way overshoot the desired result.
IMO.
Anyway, then check what the transfer case angle is. Hopefully the 2 angles will offset at 1-3 degrees. If it's really off (like if your spring design is something really weird) then you have to drop the transfer case a little, again keeping in mind that the pinion angle will change while doing that.
That said, my method consists of "The angles aren't zero. There's no vibration. We're done."
“There should be no pinion angle (0-degrees) on acceleration, or vibrations, power loss, and universal joint breakage can result,” said drag race chassis builder Jerry Bickel.
Not disagreeing one bit on the issue, but if you look at the two images, the angle at the u-joint in the bottom image, the stock, OEM style driveshaft, it's not even remotely close to 0 degrees. With the stock driveshaft configuration, ideally, the transfer case output and the pinion gear are parallel. We set the pinion a degree or two below parallel so that when you accelerate, and the leaf springs twist, causing the pinion nose to raise, they are now parallel.
In the top image, a SYE equipped configuration, you can easily see that the pinion gear and driveshaft are parallel. You are absolutely correct that you don't want it to be perfectly parallel because the bearings wouldn't rotate at all.
The OP has the original, slip yoke style driveshaft. Please stop confusing the situation.
Last edited by Jim Malcolm; 08-26-2023 at 07:34 AM.
Reason: grammer
Also, I don't believe shim determination is a straightforward "subtract this from that and that's what you need for a shim". As you pivot the differential, you are also changing the driveshaft angle, so the "simple" calculation will way overshoot the desired result.
Shim determination is a challenge with a SYE since you're trying to mantain parallel between the pinion and the driveshaft. When you insert a 1/4" thk shim, it changes the geometry...
For an OEM-style, slip-yoke driveshaft, since you're maintaining parallel between the transfer case and the pinion gear, dropping it by any amount doesn't affect the geometry. Buy the shim the measurements say are needed.
The OEM-style driveshaft becomes an issue when the angle the u-joint must operate at becomes too large, leading to vibration and eventually the yokes bottoming out on each other. High clearance yokes get you a bit more than stock, but eventually you have no choice.
Last edited by Jim Malcolm; 08-26-2023 at 07:41 AM.
Reason: grammer
Engine: 4.3L with headers and full 3" exhaust system
I am going to chime in again. No disrespect to anyone, but the angle of the driveline is irrelevant as long as you don't exceed the angle of the amount of flex the joint and yoke can handle. Again, the angle of the driveline is irrelevant. As soon as you put anything in the back of the rig, it changes because it is supposed to. And this is not a four link dragster with a 1000 hp involved on a perfectly flat track. To explain this further, I would direct you to Tom Woods Driveline website. When the joint flexes, the driveline no longer moves in a perfect circle on that end. It moves in an oval and changes velocity. So the trick is to match the angle of the Ujoint on both ends as the angle of the driveshaft changes. It is those angles that have to match, or in more practical terms be within 4°. When they don't match, they are no longer in harmony and a vibration will be felt. So I want to repeat, ditch that driveline angle measurement. The pinion shaft and tcase output shaft have to be as parallel as possible. This is an easy thing to do, shouldn't take more than 5 minutes to figure out. Then you just have to find the right shim
He's already measured the xfer case output as pointing down 4-degrees, and the rear pinion is pointing down 6-degrees. His pinion needs to rotate up. Ideally to around 2-degrees up, which means 8-degree shims. He's looking for someone to say "I did a 3.5" lift and use XX degree shims". The best answer is to measure since the answer is highly dependent on the rear springs.
I will also suggest checking your motor and trans mounts to see if they need replaced, as those will affect the xfer case angle.
08-25-2023, 07:30 PM
