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yet another driveline angle question(searched)

outlander

NAXJA Forum User
Location
Columbus,Ohio
I spent a total of two hours searching this subject here on this forum and on another.....so I feel I'm well searched.I understand driveline angles but don't understand why alot of people can't seem to nail down what size shim they need from the start.Seems like most people go about it by trial and error.

in all my searching I found no mention of how much the ds angle decreases in relation to the change in pinion angle from adding shims.Seems like pinion location in relation to the axle tubes( axle centerline) would have a direct effect on how much the ds angle would change after adding shims....correct???
edit:I take that back....there was mention that shims change the angles about 1.5 times the degree of the shim(if you have a 4* shim you will see 6* of change???)

Say for instance you have a axle that has a low pinion,like a lp d-30 found in newer xj's and you shim it 4*
then take an earlier model high pinion d-30 and shim it 4*
How would the ds angles be effected differently on the two axles due to their varying pinion locations???
Seems like the high pinion would see a more dramatic change,no???
 
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Do you mean in the front or rear. 30's are used in the front. Im not sure if Im thinking of this right. Just want to check first.
 
You only use shims in a leaf sprung axel. That would be the rear of the XJ. The front is adjusted by control arms, if you have adjustables. I would have to say that 4 degrees is 4 degrees high or low pinion. IMO....???
 
Right Raptor. Yep when people are talking shims I always thought they meant rear. Thats dana 44 or 35 etc. I know what you mean though outlander. There should be a formula for figuring out what shim is needed. Im not a mathamagican, so I cant do it :) I used ubolt eliminators and didnt have to deal with shims. The fronts are actually shimable at the factory lower arm but its not much. Like rap says, the fronts end up with adjustable arms do set it up right.
 
I am talking about rear driveline angles....I was using the pinion location differences in the two axles as an example.....sorry I didn't make myself clear.
 
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What rear do you have? What style shaft do you have? If you are running a CV shaft you want the pinion to point straight at the TC. If you are running stock u-joints you need to split the angle, pinion and TC.
 
Well, I'll throw a couple of cents worth of "notions" out here. The angle your trying to adjust for is the "operating" angle of the u-joint--not really the drive shaft angle. It's the angle created between the pinion angle and the drive shaft angle; or the angle you want the u-joint to operate at. To adjust this angle, you either rotate the pinion up or down, to bring the operating angle into an acceptable range. As you rotate the rear axle, it either simultaneously raises, or lowers, one end of the drive shaft, which also influencing the operating angle of the rear u-joint. This complicates the calculation of a specific shim, because you have two variables to solve, simultaneously. With thought, someone with an understanding of math:lecture: could right the equation required, that would solve the amount of rear axle rotation required to result in the specific amount of rear u-joint misalignment. For most of use, it's just quicker to do it:cheers:
 
Outlander, you are WAY overthinking this.

If you rotate the axle tube 4*, the entire housing rotates 4*.

The pinion may move up or back or around an undetermined number of inches, but it all has to rotate the same four degrees...

Robert
 
ColoradoRaptor said:
What rear do you have? What style shaft do you have? If you are running a CV shaft you want the pinion to point straight at the TC. If you are running stock u-joints you need to split the angle, pinion and TC.

yes I know.....
It just seems like there is alot of confusion out there regarding how to measure rear driveline angle.....
alot of the advice I hear seem to recommend measuring the pinion angle with a protractor and then measuring the driveshaft angle(slope),then subtract the pinion number from the ds angle and using that number to decide what size shim to run.but.....
by raising the pinion angle via shims also moves the ds angle.RCP Phx where are you???

Isn't it more simple and accurate to remove the ds and measure t-case output angle and then pinion angle?Therefore eliminating the guess work and need for trial and error when it comes time to select the right shim,or setup perches for pinion angle.

I guess what I'm trying to say is why even bother measuring the ds angle(or slope) when you can "go straight to the birds mouth" so to speak and take that measurement right from the t-case output yoke.....

Maybe I am looking too far into this.....tell me I'm crazy.Its been realllllyyyyyy cold here lately so I haven't been able to crawl around under the rig that much and I'm waiting on my shims to arrive from rubicon express so I'm just trying to get my ducks in a row.
 
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My "wordy"--but somewhat accurate dissertation above--still stands: you are not measuring rear u-joint "operating angle" when you measure the pinion angle. It's a proxy. It's mathematically possible to set up an equation to compute the exact change in operating angle of the u- joint, given you determine all of the parameters of the two triangles. Triangle one being the rear shaft with respect to a specified horizontal surface, and triangle two being the rear pinion angle with respect to the same horizontal surface. Since these numbers would be different for every application of drive line length, transfer case output shaft angle, and lift, it's just more practical to do the trail and error method.
The operating angles of the u-joints are not supposed to be spot-on. In fact, there MUST be some misalignment (~1/2*), or the bearings will wear out post haste.
Additionally, whether or not you have a double Cardin jointed shaft, the rear joint needs 1.5 to 3.0* "error", with the pinion rotated downward, to account for the upward rotation of the pinion upon placing a load on the rear differential. If you have a rear ladder bar, or rear linked suspension (Grand Cherokee), the down ward pinion angle will be much less, but still a little.
 
xjbubba said:
My "wordy"--but somewhat accurate dissertation above--still stands: you are not measuring rear u-joint "operating angle" when you measure the pinion angle. It's a proxy. It's mathematically possible to set up an equation to compute the exact change in operating angle of the u- joint, given you determine all of the parameters of the two triangles. Triangle one being the rear shaft with respect to a specified horizontal surface, and triangle two being the rear pinion angle with respect to the same horizontal surface. Since these numbers would be different for every application of drive line length, transfer case output shaft angle, and lift, it's just more practical to do the trail and error method.
The operating angles of the u-joints are not supposed to be spot-on. In fact, there MUST be some misalignment (~1/2*), or the bearings will wear out post haste.
Additionally, whether or not you have a double Cardin jointed shaft, the rear joint needs 1.5 to 3.0* "error", with the pinion rotated downward, to account for the upward rotation of the pinion upon placing a load on the rear differential. If you have a rear ladder bar, or rear linked suspension (Grand Cherokee), the down ward pinion angle will be much less, but still a little.


x2 Thats what Tom Woods told me. You want some difference in the angles to make the bearings in the ujoint roll instead of just stay in the same place. In theory it also torques the shaft up a little while accelerating. I went with 2 degrees.

DSC00468.jpg



DSC00474.jpg
 
Outlander,I'll try to help!
On a 2 joint shaft you want the pinion angle to be the same as the tranfer case output shaft(we wont talk about axle wrap or operating angles,yet).On a typical XJ the output shaft is about 4* down,so if your pinion was at 0* then you would need a 4* shim.If you have any axle wrap,you may need to reduce that by a couple degrres.If your exceeding the joint operating angles,you could drop the transfer case to like 6* and shim the axle up to 6*.
2joint_angle.gif

Now,on a CV driveshaft you want the pinion angle to equal the driveshaft angle.When shimming with this setup you get a "total net change" of about 1.3-1.5x degree on the shim(it actually varies depending on driveshaft length and shim degree).Example:If your driveshaft was 15* down and your pinion was 6* up,you need a change of 9* so you would use a 6* shim(6* x 1.5=9*).
cv_angle.gif
 
RCP Phx said:
Outlander,I'll try to help!
On a 2 joint shaft you want the pinion angle to be the same as the tranfer case output shaft(we wont talk about axle wrap or operating angles,yet).On a typical XJ the output shaft is about 4* down,so if your pinion was at 0* then you would need a 4* shim.If you have any axle wrap,you may need to reduce that by a couple degrres.If your exceeding the joint operating angles,you could drop the transfer case to like 6* and shim the axle up to 6*.
2joint_angle.gif

Now,on a CV driveshaft you want the pinion angle to equal the driveshaft angle.When shimming with this setup you get a "total net change" of about 1.3-1.5x degree on the shim(it actually varies depending on driveshaft length and shim degree).Example:If your driveshaft was 15* down and your pinion was 6* up,you need a change of 9* so you would use a 6* shim(6* x 1.5=9*).
cv_angle.gif
By far the best answer and example for DS angles I have seen yet.:cheers:
 
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