[gregg bowie]

Just installed rocky-roads trailblazer 4" susp. lift and BFG 33" M/T's on my '04 Rubicon. Test ride revealed vibration problems. I was told that the Rubi did not need the T-case lowering kit or the slip yoke eliminator. Kit did not come with adj. control arms so driveshaft/pinion angle increased slightly. What is the solution? Can't live with the vib, so if it can't be worked out, it's coming off.

Thanks for any advice,
Gregg Bowie

 

[bluvikng]

You are correct about not needing to drop the t-case. However, I am not familiar with the type of lift that you have. One thing that can be causing this problem is incorrect wheel base spacing. Did your lift come with longer lower control arms? Did it come with risers, for front and rear track bars? There are so many causes to this problem. Is there enough clearance between the ears of your driveshaft vs. yokes? If nothing else, you can lower the skid plate with washers, that way you can get away with minimum loss of clearance. Another trick for the driveshaft, is to shave the ears with a grinder, to where they do not hit each other. A slight touch here, will cause a lot of vibes on the road.

Does your Rubi have an automatic? If so, you have a shorter rear drive shaft than a standard transmission. Two things you can do here......shim down the skid plate, or buy a shorty double cardon drive shaft.
One other fix that we did on another 03 Rubi w/auto trans......installed adjustable upper control arms, and changed the pinion angle, to decrease the angle of the driveshaft.

 

[MR.CLIFFORD]

4" of suspension lift will give you vibes on almost any stock drive shaft. Just because you were told you don't need it doesn't mean that is correct. Best course of events would be to determine your rear drive shaft is the exact problem. Pull your rear drive shaft and drive around in 4hi. Pull up to 40-45 and see if your vibe is gone. If it is then you know your rear drive shaft is the culprit.

I see a CV style drive shaft, adjustable control arms, and a vibe free rubicon

If your vibe is still present after the rear DS is disconnected start checking the obvious. Did you align your jeep after the lift? Does the Rocky Road kit come with a way to correct the offset axles via track bars??

 

[bluvikng]

Foot note:
Upper control arms maintain pinion angle.
Lower control arms maintain wheel base.

 

[gregg bowie]

Thanks Guys

My rubi has a standard tranny. The ears on the yokes are not touching. The kit did not come with, or was available with, new control arms of any kind. It did come with front and rear adjustable track bars, but NO instruction on how to set them or how to do ANYTHING else. Not one word of instruction, just 4 coils, 4 shocks, 1 drop pittman, and 2 adj. track bars.
Thanks for the replies, I'll give them a try.

Gregg

 

[bluvikng]

This is amazing. I went to Rocky Roads web site, and read all of their stuff about their 4" lift. One of the things they brag about, is the fact that they have very easy instructions to follow. The 4" lift that I put on our Jeep came with longer lower control arms, and risers for the track bars. You obviously have already installed the lift. Do me a favor, measure the wheel base of your Jeep, center of front axle, to center of rear axle. It should be no shorter than 92 inches. I also have a manuel tranny, and have absolutely no vibes, with the skid plate mounted at factory position. I did not have to use the spacers that came with the kit, to drop the skid plate. Again, measure your wheel base, and let me know what you came up with. Also, you should not need to replace your upper control arms. You may need to get the longer adjustable lower control arms, to get your wheel base corrected. Let me know.

 

[jeeperman]

You WILL need new control arms, at least lowers. You need to change the pinion angle to match the driveshaft angle (it will be worse in the front than rear because of the d-shaft length). I don't know how they thought that there wouldn't be any vibes with stock length control arms...

 

[MR.CLIFFORD]

You WILL need new control arms, at least lowers. You need to change the pinion angle to match the driveshaft angle (it will be worse in the front than rear because of the d-shaft length). I don't know how they thought that there wouldn't be any vibes with stock length control arms...

lowers aren't made to adjust pinion angle in the rear. Upper control arms do that job. And you don't match the pinion angle to the driveshaft angle. On any rear setup you should aim for 2 degrees down to allow for pinion roll.

 

[MR.CLIFFORD]

Not one word of instruction, just 4 coils, 4 shocks, [bold]1 drop pittman[/bold], and 2 adj. track bars.


Gregg

This bothers me. You do not need a dropped pitman arm for a 4" suspension lift. Your drag link and track bar should be as parallel as possible. If you installed the drop pitman arm without modification to the track bar mounts then your steering angles are out of whack and will not function properly.

 

[jeeperman]

lowers aren't made to adjust pinion angle in the rear. Upper control arms do that job. And you don't match the pinion angle to the driveshaft angle. On any rear setup you should aim for 2 degrees down to allow for pinion roll.

You are correct, sorry. I am used to adjusting with the lowers in the rear due to my 3 link in the back... And I did mention the pinion being 2 degrees below d-shaft angle in the other post about vibes, thought I did in this one too... Thanks for keeping me in check, otherwise I just run wild!!!

 

[gregg bowie]

Measured wheel base as you suggested. Came up with 92 1/4".
Is this OK?

Gregg

 

[bluvikng]

That is good. No problem there.

 

[gregg bowie]

I am considering re-drilling (relocating) the rear upper control arm mounting holes to lessen the pinion angle. I believe this will help reduce the angle and there is plenty of metal there to do it. What do y'all think?

Gregg

 

[bluvikng]

I don't know if that is a good idea........having multible holes in that area would decrease the strength of the metal. That is a very vital part that takes a lot of stress. How far are you needing to move them?

 

[gregg bowie]

I would say no more than 1/2" forward. I got the idea from reading about Nth degree lift kits which come with control arm relocation drill templates. I might add that this jeep will be on- road 99% of its life and when off-road it will be in the mud, NO rock climbing as there are no rocks in east Texas.

Gregg

 

[bluvikng]

You haven't been to Gilmer than.......lol. What a fun place that is too wheel. Now that you mentioned Nth deg. they have adjustable upper control arms. I would highly recommend that over drilling. If you go with their arms, get the shorter ones. The longer ones are too long. If in doubt, measure the distance between the two mounting points.