After adjusting my lower control arms shorter (23.5") to achieve a better front drive angle.
I still have a slight vibration.
I really didn't want to take any more caster out of the front end because it is a little bit "twitchy' now.
I decided to take the drive shaft out and go for a drive to make sure that it is the problem.
Well , it is not the problem. I still have the harmonic vibration at 50-55 mph even without the drive shaft installed.
I guess I will reset the lower control arms to 23 3/4" and put the front drive shaft back in it.

Now I have to check the rear 1310 shaft.

I really don't think that the vibration is coming from the tires, but I will go ahead and rotate them anyway. Maybe I should wait until I rotate the tires and give it another test drive before I put the shaft back in.
That way I can eliminate one thing at a time.


Question, Has anyone had trouble with a rear 1310 aftermarket drive shaft??

 

honestly, anything more than 23" seems like a lot lower control arm adjustment to me. if anything, i might shorten up your front upper arms instead but, that's just me.

regarding the vibrations that you have, sounds very much like it your rear shaft. did you make sure to set your pinion angle so that it's in line with the drive shaft? you would have needed adjustable rear upper control arms in order to do this. if you have not, that is your problem.

 

Yes I am running the Teraflex front and rear upper and lower adjustable control arms.
I will take another look at the rear to see if it is perfectly in line.
I just set the rear control arms to the Teraflex recommended lengths.
Just eyeballing it, it looks to be lined up.

As far as the front lower arm lengths go, 23 3/4" is actually less than the Teraflex starting length, which is 24" for an unlimited.
I am running 37's and I thought it would give me more clearance for the tire at the rear of the front fender opening.
I did notice that the front springs seam to be more in line, top to bottom, (when looking from the side of the jeep .)
When set at the Teraflex specs the front is pushed forward quite a bit.

Do you have any clearance issues with yours set at 23" ?

Thanks for your input, I am just trying to get this thing dialed in right.

 

factory arms are 22-5/8" eye to eye. 23-3/4" is more than an inch longer and in my opinion, way too long but hey, what do i know.

i'm sure it is and i'm surprised that your coils aren't making contact with your sway bar.

no. i have worked on a lot of jk's and installed a bunch of different lifts and have never found 23" to be a problem. where i have seen problems is with control arms set to 24".

regarding your rear drive shaft, use an angle finder to make sure you are on. if it is, could be that you are too on and may need to compensate for the change in angle caused by axle wrap.

 

Hey man I really appreciate your response.
I will reset the front lowers to 23" this afternoon after work and shorten the uppers to 18 7/8" and see how it goes.