Are the Rusty's ones double adjustable?
Mine are single adjustable. It sucks dick to align the axle.
Getting up to highway speed without shaking apart (05 LJ)
- Thread starter RexTreks
- Start date
Are the Rusty's ones double adjustable?
Mine are single adjustable. It sucks dick to align the axle.
OP
Exactly right,
They appear to be only single adjustable, I can imagine that isn't the most fun
OP
So I took some measurements with the gauge and found the following....
I
- The skid spacers from the lift kit seems to have angled the T-Case by 9*.
- The rear pinion sits surprisingly high at 10*,
- I imagine that the rear lower control arms are shorter than the OEM ones, in order to pitch it toward the down-angled Tcase.
- The lowered rear of the tcase of course means a higher incident angle (+9*) of the front shaft,
- I assume the "cheat" of using spaces is to try and get away with the stock DC front driveshaft that can better cope with the total 18* of deflection.
- On top of that I imagine that the front lower control arms are shorter than the OEM ones, in order to pitch it up to relieve some of that additional angle.
- I imagine that the reason why the front driveshaft can better cope with this is also because it is longer than the rear unit?
From my understanding of the above, it seems likely the problem is probably due to the increased strain on the front driveshaft joints because of the t-case spacers.
This leads me to wonder;
- why did the lift kit even bother including them in the first place if the proper geometry of a 2-Joint shaft is to have the pinion and tcase angles at 0*?
- would I benefit from simply removing the tcase spacers and swapping in adjustable upper control arms to bring the pinions as close to 0 as possible?
Exactly right,
They appear to be only single adjustable, I can imagine that isn't the most fun
Shits fuckin annoying. And not just time consuming. Every fucking time you make an adjustment... Using the centering punch to pull the bolt holes into alignment. That passenger side next to the muffler...
Bruh. It's ass. Spend the money on double adjustable
OP
Shits fuckin annoying. And not just time consuming. Every fucking time you make an adjustment... Using the centering punch to pull the bolt holes into alignment. That passenger side next to the muffler...
Bruh. It's ass. Spend the money on double adjustable
at the low low cost of twice as much money, hahaha, but hey the way you make it out to be seems to be a bargain.
So I took some measurements with the gauge and found the following....
Icreated an abominationtook some liberties with the above image of course...
View attachment 472943
- The skid spacers from the lift kit seems to have angled the T-Case by 9*.
- The rear pinion sits surprisingly high at 10*,
- I imagine that the rear lower control arms are shorter than the OEM ones, in order to pitch it toward the down-angled Tcase.
- The lowered rear of the tcase of course means a higher incident angle (+9*) of the front shaft,
- I assume the "cheat" of using spaces is to try and get away with the stock DC front driveshaft that can better cope with the total 18* of deflection.
- On top of that I imagine that the front lower control arms are shorter than the OEM ones, in order to pitch it up to relieve some of that additional angle.
- I imagine that the reason why the front driveshaft can better cope with this is also because it is longer than the rear unit?
From my understanding of the above, it seems likely the problem is probably due to the increased strain on the front driveshaft joints because of the t-case spacers.
This leads me to wonder;
- why did the lift kit even bother including them in the first place if the proper geometry of a 2-Joint shaft is to have the pinion and tcase angles at 0*?
- would I benefit from simply removing the tcase spacers and swapping in adjustable upper control arms to bring the pinions as close to 0 as possible?
Hm. Not sure if this is a meaningful contribution, but I never measured my tcase angle. It's more about relative angle between tcase and pinion afaik, rather than the angles themselves.
The answer might be as simple as people selling the kits aren't as particular as we are going to be here, or are just pushing cheap product for profit.
Skid plate spacers are a bandaid for another issue so I'd think regardless of these angles it should be a goal to remove them and make it work.
How much money you got and how much free time you got I guess is the question...
LONGJP2
TJ Expert
Don't worry about the front shaft (yet).
Its factory DC joint shaft can handle the angles better.
The transfer case will not be level to the ground. In fact, a Motor Mount Lift is often used to tilt it down in the back to increase the rear output angle.
Lowering the tcase with the spacers does the same thing, but you lose ground clearance.
Not sure what you mean by 0°. With the rear factory (2 joint) shaft. The pinion angle up should match whatever the tcase output angle down is.
OP
I've got a feeling you're on to something here!
Seems like they're gonna be the first things to go here in this equation - couldn't hurt to test it out, especially for free.99.
OP
Ah, in this context I meant as deflection from parallel to flat ground.
The motor mounts and the tcase spaces seems like they would be an OK-ish bandaid solution to getting reduced angles on the rear driveshaft.
Theis diagram confuses me in that aspect, why wouldn't you want to simply align the differential to the driveshaft as much as possible, even if you don't have a DC/CV driveshaft?
is it because the cardan joints REQUIRE equal angles in order to harmonically counteract themselves? in so much that they dont have to be level with the ground but they must be equal?
Might be having a lightbulb moment here.
LONGJP2
TJ Expert
Correct.
Nothing has to be level to the ground, too bad that diagram implies that.
It's relation to what it's connected to is what counts.
https://4xshaft.com/blogs/general-tech-info-articles/driveshaft-angles
The motor mount lif is not necessarily a bandaid, while the tcase spacers are. Why? One reduces clearance off-road which is what you're building for. One doesn't. The MML is giving the tcase an angle that is easier/better for aligning the axles properly. The skid spacers are translating it downwards to change the angle. Accomplishing the same goal in different ways, but one is sacrifing other things
There are some good videos on YouTube that show how the different joints react at an angle of you're curious
OP
LONGJP2
TJ Expert
Hate to nitpick, but how are the 2 ways doing anything different?
The engine/transmission/transfer case assembly is only supported at each end.
Raising one or lowering the other would give the same result.
The MML translates the engine, which changes the angle of the tcase, and thus what you need to do to the axles to obtain optimal relative angle, without translating it.
The tcase drop translates the tcase sacrifing clearance, which also changes what you need to do to the axles to obtain that relative angle in a similar way.
They're very similar for sure but different. If you could translate the tcase without sacrifing clearance it'd be effectively the same... But you can't, making one a bandaid and one not for the sake of offroading. If you don't offroad, it don't matter. That's my thinking anyways
OP
OK - I didn't measure the transfer case rear output angle correctly, going to get fresh measurements on that shortly.
Also, now having read more on joint types, I'm not going to focus on on the front driveline at the moment, back shortly with numbers.
OP
Okay so I think I found the problem, the pinion angle is set to a higher angle than it should be by about 2*.
its currently OVER the relative angle of the driveshaft so instead of subtracting the phase wave it is adding to it.
I also read from a Tom Woods resource that you should set the pinion angle to -1* from the transfer case output angle.
My solution is to install rear upper control arms and reduce the pinion angle from 9.5* to 7.5*
Thinking we've got the solution in the bag boys.
its currently OVER the relative angle of the driveshaft so instead of subtracting the phase wave it is adding to it.
I also read from a Tom Woods resource that you should set the pinion angle to -1* from the transfer case output angle.
My solution is to install rear upper control arms and reduce the pinion angle from 9.5* to 7.5*
Thinking we've got the solution in the bag boys.
That extra 1° recommended by TW is due to deflection of the axle during acceleration/load I think? And can vary depending on what your drive line will allow without vibrations (I'm a TJ guy so alot of these concerns of mine maybe won't be as prevalent for you)
IIRC I was fairly verbose while figuring this out in my build thread if that might help. But sounds like you've got a decent grasp on it but now.
OP
I'd be happy to read it through! I just placed an order for rear uppers and we'll see how getting the pinion under rather than over helps with the vibrations. I ended up going with Core 4x4's entry level adjustable rear upper, and go from there.
I have core 4x4 but theyve redone their "tiers" since. Is that rubber/rubber? I actually got away with not getting front uppers IIRC.
Good luck my guy, get a centering punch