Topic: Vibration

[Liljeepz]

I have a question about Vibration.
I just instaled my JKS ACOS yesterday, now when i drive it I get a slight vibration when I hit my peek power rpm. Seems to hit 2500-3100 RPM but not before and not after. Its not bad, If i have my radio on I dout I would hear it and it feals like im going over little groovs in the pavment.... not like the grooves before a toll, but like cracks in the road.
Is this normal? Will it do damage to the transfer case if I don't fix it right away?
I set my rear as low as it can go... so thats about 2" or a hair over
The frount may be a tad higher 2 1/4" at the most.
I had the frount set at 2 but it looked funny. I have my soft top on now and the butt of the jeep stuck way up.
I coulld get a CV/SYE in about a month or so if I had to. But I would be spending my rim/tire money.  :cry:

[Jeffy]

It's probably the driveshaft.  There are a few way's you can go about this;

What's the angle of the driveshaft look like?  I believe there is some adjustability in the stock control arms.  I'm not 100% on it though.  You probably need to rotate the axle a bit now that it has more lift.

Other option would be to raise the engine with a 1" MM lift.  Another would to add cam'ed bolts to adjsut the rear housing angle.  The worst of the bunch would be to lower the transfer case.  The most expensive would be to install a SYE.  Although that can be done pretty cheap on a TJ.  SYE kits are as low as $99 for a hack and tap.  Then $150-200 for a lengthened driveshaft.  (Probably don't need a CV.)

[Liljeepz]

With the 1" MM... would I need to do any thing elce? I thought I would have to rase the radiator too.
I went under there and looked, I did not see any way to rotate the axle.
There is also no adjustability in my stock control arms that I could see with out pulling stuff off.
I don't think it is the front end that is doing it tho, when I put it in 4WD
its almsot gone.
I did jsut get back from geting an allingment. that seemed to help, It only dose it in 2nd gear at around 20-25 mph now.
the jeep guys said to jsut drop the Tcase. I don't want to lose any clearance but it would be a fast cheep fix if I could find a 1/2" drop kit.
I don't think I need a lot.
Ill post pics as soon as I find a webhost to host the pics. (you know any good free ones?)

[Liljeepz]

Thats the front.

Thats the rear.

[zeitlerusmc]

did this happen right after you lifted it? what size lift do you have on it

[Liljeepz]

I set the ACOS at 2"
I think Im going to get a 1"BL and 1"MML
If I can talk my wife into it that is.
I think I can drive her car tell I get it this weekend.

[Jeffy]

I set the ACOS at 2"
I think Im going to get a 1"BL and 1"MML
If I can talk my wife into it that is.
I think I can drive her car tell I get it this weekend.

You know before doing anything really expensice, I'd consider these.

http://www.quadratec.com/products/16105_50.htm

I'm sure there are others out there too.

[Liljeepz]

<edited>
That looks like it moves the rear uper control arm, so that it tilts the axil to reduce the drive line angle?
 is that corect?

[Liljeepz]

From what I have read up on those, they only seem to give you 1-2 dagrees of change, I think I may be more off than that.

[Liljeepz]

JKS BL and MML on order. I hope that fixes the problem, or my wife is going to kill me!

<update> MML is on back order 2-4weeks!!!  :shock:
                Not sure what im going to do, I can live 1 week with out a car,
                but 2-4?!!

[Bounty Hunter]

I've lifted a lot of coil-sprung jeeps the same amount and never needed a TC drop or those other mods to remove vibes.  Your rear driveshaft setup looked fine as best I can tell without an angle finder.  Pic of front is worthless as it doesn't show the pinion.

I recommend running the caster out as far as possible, you'll need to get the adj. cam bolts if your jeep didn't come with them on the front LCA's.  Should get rid of most or all vibes and improve handling.