Topic: '93 yj vibration at 40 mph

[SamsonJR]

hey guys, this ones for my fiances '93. has a bad vibration and loud humming kind of noise only when you hit 40 mph, 6 inch suspension lift, 35x12.50 tires. tires have been balanced and front end was aligned. it drives pretty strait, I'm going to order a new steering stabilizer soon, it had the stock one and a skyjacker dual on the drag link. I removed the dual and the steering doesn't have as much resistance but same problem. I had the front driveshaft done not to long ago and it was balanced, the yoke has some play but nothing crazy. I removed it and drove and still doing it. I removed the rear shaft, and drove it in 4x4 , it wandered real bad and still did it. I'm stumped. Also sometimes if you hit a bump with the left front tire, it gets a bad wobble on the drivers side. I jacked the jeep up and pulled the wheels back and forth to check for play in the hubs but they seem fine. I don't know what it could be. thought I'd ask you guys if you had any ideas. She wont drive it until I fix it, and I'm lost.

[neale_rs]

Check for play in the ball joints and the tie rod ends.  You can have someone move the steering wheel while you look at the moving parts.

[dwtaylorpdx]

Google Jeep Death Wobble... LOL

Dave

[Jeffy]

Google Jeep Death Wobble... LOL

Dave

You don't usually see that on a YJ though.

[sharpxmen]

sounds like more than 1 issue

for the d/s hitting a bump, have a look at the shock absorber on that side, also check the caster angle

for vibration, since you pulled the rear d/s should rule out the rear axle (not 100% though), check the trans and motor mounts

 - and the suggestions on the balljoints from neale

[Jeffy]

sounds like more than 1 issue

for the d/s hitting a bump, have a look at the shock absorber on that side, also check the caster angle

for vibration, since you pulled the rear d/s should rule out the rear axle (not 100% though), check the trans and motor mounts

 - and the suggestions on the balljoints from neale

+1

I'm gonna guess his Jeep has some bumpsteer among other things.

[dwtaylorpdx]

You don't usually see that on a YJ though.

Mine did a darn fine imitation of it when the tie rod end failed... LOL

Worn out spring bushings can contribute.. 

CHeers
Dave

[SamsonJR]

hey guys, thanks for all the input! I checked out the bushings. they look alright. balljoints seem fine as do the tierods. the tie rod on the drag link at the pitman arm looks a little worn. Im not sure if its from the dual steering stabilizer twisting so hard? I took  a look at the shocks. and sure enough, the left d/s has more play then the rest. the shocks in my jeep are a few months old. I did the push test and mine and it hardly moves. a good push on Rachele's, and the whole jeep bounces. I think I found the death wobble culprit.  I got the part numbers off the shocks. there from the lift that was put on. skyjacker shocks. There about 45 a piece, once I get paid I'm going to order 4 new ones and a steering stabilizer. hopfully that corrects the wobble. as for the vibration, how do I check the caster on the front axle? the vibration sounds like its coming from the bellhousing area when I drive it, but it's hard to tell

[sharpxmen]

the caster was for the death wobble not the vibration, sounds like you have the answer for the moment at least with this issue so test again once you replace the shocks.

have you checked the motor and transmission mounts, they can cause vibration if it's resting metal to metal or if the supports to the frame or risers are cracked. (for the vibration). Now, i'm sure it's not the case but i'll ask anyway - when you say vibration you mean you feel it in the steering, floor, etc or do you actually hear it? if you just hear it then look for something loose or touching (the exhaust downpipe touching the transmission, cat touching the trans or skid or having the hanger busted, the inspection cover at the bellhousing if it's missing bolts is another one)

[dwtaylorpdx]

Check the pinion angle too.. It is related to caster on a solid front end, occasionally folks put in lifts with shims not understanding that the cast can be tweeked.. But that usually just makes the jeep twitchy....

On my YJ the rear tranny mount got tired and started transferring vibration into the skid plate..

Dave

[grumpygy]

Just something to look at What Material is the Motor and trans Mount made out of.

[sharpxmen]

Check the pinion angle too.. It is related to caster on a solid front end, occasionally folks put in lifts with shims not understanding that the cast can be tweeked.. But that usually just makes the jeep twitchy....

On my YJ the rear tranny mount got tired and started transferring vibration into the skid plate..

Dave

unless he has a CV up front bringing the caster back to stock will bring the pinion angle back to what is needed (will be back parallel to the t-case output yoke). If he's got a CV then fixing caster will require realigning the Cs at the end of the tubes while the pinion yoke angle would be in line with the front driveshaft.

[SamsonJR]

Ok, so I have to wait to order the parts on thursday, as for the vibration, I can feel it threw the floor in the front by the t case shifter, maybe closer to the firewall, it's a dull vibration, I can hear it as well. As for feeling it threw the steering wheel, The jeep has some bad bump steer right now, the only time I feel any vibration in the wheel is when I come to a complete stop, and that's only when the jeeps just about fully stopped. I'm not sure what the mounts are made of, I looked at the tranny mount wile I was under the jeep removing and re installing the d/s's. it appears to be rubber. as for the motor mounts, I'll check them out tomorrow, I did'nt check for exhaust contact or anything like that. When it's light out I'll look for metal to metal contact. Oh, and I forgot to mention, it's not at 40 mph, the speedo gear needs to be replaced, it's probably more like 50 mph. But no noise/ vibration above 60ish? or below. No CV upfront btw

[dwtaylorpdx]

unless he has a CV up front bringing the caster back to stock will bring the pinion angle back to what is needed (will be back parallel to the t-case output yoke). If he's got a CV then fixing caster will require realigning the Cs at the end of the tubes while the pinion yoke angle would be in line with the front driveshaft.

Yep! but wouldn't it depend on the type of lift if any? my Tcase drop , causes the front yoke on the tcase to tilt up a bit. I've never had any issues with the front vibrating, but in the rear my original lift had shims, And vibrated occasionally when the u-joints got worn. when I converted to D44 I had to have brackets put on the new rear end, and we corrected the pinion angle without needing the shims, so that's a plus..

Cheers
Dave

[sharpxmen]

Yep! but wouldn't it depend on the type of lift if any? my Tcase drop , causes the front yoke on the tcase to tilt up a bit. I've never had any issues with the front vibrating, but in the rear my original lift had shims, And vibrated occasionally when the u-joints got worn. when I converted to D44 I had to have brackets put on the new rear end, and we corrected the pinion angle without needing the shims, so that's a plus..

Cheers
Dave

if you correct the caster angle with shims (with no t-case drop) the pinion yoke angle will be back to what it was before, or the other way around, if you fix the pinion angle (so it's parallel to the t-case front output yoke) the caster angle will be back to the same value, it's all welded together so you increase/decrease one of them the other will follow by the same amount. Type of lift will not alter the relation between the caster angle and the pinion angle, once you correct it you're back where you were before the lift on both (caster and pinion yoke).