Good Vibrations?

Here's the deal. I have a '91 xj with about 3.5" of lift running 31" MTs. I have no sway bar in front or rear and i have a "Selec-Trac" t-case with the full time option. When I'm drivin above 45mph and in 2wd, everything vibrates, and I mean the whole jeep is shakin like hell. When i drop it in 4 full time, however, it glides across the road like a family sedan. Do i need an alignment? What else might cause this?

When did you lift it? It is most likely due to your driveline angles. You can start with a transfercase drop and see if that cures your problems. if not, your gonna be looking to get a new driveshaft and slip yoke elimintator. If you lifted it recentley, and have not had an allignment, you should do that as well to save your tires.

But if it were the driveline angles, why would it stop in full time 4 wheel drive? I lifted it early last year and got it aligned when I had my stock 27" street tires. My MTs don't seem to be wearing uneavenly.

has it vibrated the whole time? or just all of a sudden recently?

jeepinxj05 said:

But if it were the driveline angles, why would it stop in full time 4 wheel drive? I lifted it early last year and got it aligned when I had my stock 27" street tires. My MTs don't seem to be wearing uneavenly.

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Mine did this when I first lifted it with the REa 4.5 inch kit. It also had the 242 and would also vibrate when it was in two wheel drive and not in full time. I had to tilt the axle up alittle to where I had about the minimum caster I could stand...This cured the problem.
I think the front driveshaft shakes when it is turning with no load on it. In a jeep with the 242 you don't have a front axle disconect so it is turning all the time even in two wheel drive.

I also have an XJ with a 242. Mine is an '89. I put a 3" Skyjacker lift in it 18 months ago. Imediately after the lift, I installed 31"x9.50's on stock wheels, then went for an alignment. I imediately noticed vibrations in the 30-40 mph range and ordered a transfer case lowering kit. Once that was installed, vibes mostly disapeared...but not entirely.

I took it to a reputable shop requesting an SYE kit and CV driveline. He measured my rear driveline angles and recommended against...said angles were good and that vibration was likely "transmission shutter". That was over a year ago...vibes still present at 30-40 mph speed, but nothing else...no other damage.

I still want to do an SYE and CV driveline...and will, but no rush that I can think of.

I'm guessing that a t-case lowering kit would do wonders for you. Also, I should mention that my lift came with new rear springs...and they changed the angle of the axle. Your lift may not have done the same. You should check driveline angles fo the rear.

i was hoping that i could avoid the lowering kit at the risk of sacrificing precious ground clearance but will this vibration harm anything? If not then i will just deal with it. Would removing the driveshaft for street use stop the vibration? thanks for the replies.