Questions about stock pinion angle

[fuse]

Since I'm planning some upgrades, I figured I'd get some measurements of the stock setup including the driveshaft and pinion angles.

Here's what I measured for my stock 05 Sport with no changes to driveline or suspension:

The first question is, do the numbers look like they're in the right range for a stock Jeep, or should I go back and measure things again? I tried to follow the best descriptions of how to measure these angles and measured twice, but it is my first time doing it.

The second question relates to the FSM, which provides three "rules" for drive shaft angles:

• Good cancellation of u-joint operating angles (within 1*)
• Operating angles less than 3*
• At least 1/2 of one degree continuous operating (propeller shaft) angle

Things look good with the first and third rules. I've got 0.8* of u-joint cancellation, and more than 1/2* of operating angle at either end.

But my operating angles are 5.7* at the transfer case output and 4.9* at the axle input. My setup should be just what came from the factory, so what gives? Is the FSM "rule" on operating angles too conservative?

 

[jjvw]

No idea what stock was or should be. But the angles are what they are. Even with adjustable arms, there is only so much one can do to get to that 3 degrees, especially after a lift.

 

[fuse]

This post suggests that 7* is a conservative limit on the u-joint operating angle, 15* is a practical upper limit before there are real problems: https://wranglertjforum.com/threads/how-to-properly-set-your-pinion-angle.228/

I don't have any driveline vibrations and wouldn't expect to with a stock Jeep so 5* is clearly fine. I don't know how long those u-joints have been there, but they've definitely been there a while and they all check out OK.

I'm guessing the FSM just ended up with some text that was copied and pasted from the manual for a different vehicle and not updated to be right for the TJ.

 

[mots]

Curious on the tool you are using to measure? I have a digital angle tool on the way from Amazon and I will be fiddling around with some measurements myself.

 

[fuse]

No idea what stock was or should be. But the angles are what they are. Even with adjustable arms, there is only so much one can do to get to that 3 degrees, especially after a lift.

I've been thinking about that. The common recommendation for driveline vibrations after a lift is a transfer case drop (or a double-cardan drive shaft). The transfer case drop will change the operating angle at the transfer case and reduce the drive shaft angle, which are both countering the effects of the lift.

But it seems like it might be possible to deal with minor vibrations by adjusting the rear pinion angle to improve u-joint cancellation. So maybe adjustable rear (upper?) control arms could actually help with driveline vibrations after a lift?

 

[fuse]

Curious on the tool you are using to measure? I have a digital angle tool on the way from Amazon and I will be fiddling around with some measurements myself.

I used the instructions on this page: http://www.wanderingtrail.com/Mecha...riveshaft_Alignment/Drive_Shaft_Alignment.htm

And I found this page to be helpful: https://www.hotrodhotline.com/conte...ancellation-jim-clark-hot-rod-md#.XU7WNuhKiHt. But there are better descriptions and videos in the how-to that Chris posted.

I didn't use Jerry's tip about measuring the axle yoke angle from the flat spots on the back of the diff, but I will definitely do that next time: https://wranglertjforum.com/threads/eyeball-my-pinion-angle-please.8610/#post-127803

 

[pagrey]

I'm a bit confused, what are you trying to accomplish? What is the purpose of your research. I'm not trying to be negative just don't understand what you are trying to do. Most people drop the case/skid because it is much cheaper than adjustable arms and not because it is a better solution.

 

[fuse]

I'm a bit confused, what are you trying to accomplish? What is the purpose of your research. I'm not trying to be negative just don't understand what you are trying to do. Most people drop the case/skid because it is much cheaper than adjustable arms and not because it is a better solution.

Not trying to "accomplish" anything right now. Just getting measurements before making some upgrades and thinking about some options for later mods.

Re adjustable arms vs t-case drop, I was just thinking about u-joint cancellation and it occurred to me that adjustable arms could be a different and maybe more direct approach. I'm not expecting drive line vibrations with the lift I have planned, but I'm already planning the J-Flex arms as an upgrade, and it would be nice to have the option to use that upgrade to improve u-joint cancellation if I need to.

 

[jjvw]

Adjustable links, SSSYE and the double cardan rear drive shaft are the best you can do. Stock drive line specs don't really matter if the drive lines aren't stock.

I suppose you can drop the transfer case...