Front Driveline Vibes at 6" plus?

Anyone else experience vibes from their front driveline after lifting 6"+?

I didn't have any at first (after the lift) but developed after a couple months or so. Any speed over 65 mph starts vibrating/oscillating pretty bad. Don''t notice anything around town at lower speeds.

Removed the front driveline and its smooth. U-joint seems fine but am going to replace anyway with greaseable one. What are the angles that the front need to be?

It's at 6.5" front and rear with a SYE, new rear cv shaft, 6* shims and still has a 1" t-case drop from my previous 3" lift that I haven't bothered to remove yet.

Thanks.

Hey your lucky I still have a LP!!Front angles are a challenge on lifts above about 4-5".Its always a compromise of castor vs. pinion angle.BTW: you didnt say anything about your arms???Also the trans "drop kit" makes the front angles worse.One more thing is to check the slip-yoke,mines getting pretty sloppy and it wasnt all that nice when new(at 16K miles now).

Now that I have 4.56 gears I find the front vibes I used to get at 80+ mph are now present at 60+. Looks like I need to pay attention to the front drive line angle.
So how does one rotate the pinion up? Doesn't adding shims to the bottom LCA's rotate the pinion down? Or do I have to buy adj. upper control arms (UCA's)? Those adj ball joints are starting to look like a good idea.

Anyone ever looked at AEV 2 Degree Offset Balljoints? I'd be interested in reading a writeup on these.

do you have the older front driveshaft or a newer one with a CV style? just a thought

I have yet to see offset uppers and lowers!Without doing both you place the centerline of the axle off-center with the centerline of the carrier,NO THANK YOU!!!!

i had to settle for 3 degrees of caster when trying to solve my vibe problem... when my rig was first put up to 6.5 inches it was awesome.. very cadillac like.. now it rides rough and choppy and the preload/bearings/everything in the front diff is junk and i have to reset it all.. but thats from the " professional " that set the gears up.

now all i have to do is relocate my steering stabilizer.

I'll take out the TC drop and see what happens there. I've got the 5.5" RE xd kit with the drop brackets and non-adj. control arms that came with it. I'll have to dig out my alignment specs and see where they set it at.

I just got the 4.56's installed a month ago or so, didn't think that could have an affect but maybe I'm wrong? The guy is a pretty good driveline/rear-end shop so maybe I'll run it back to him to have a look see also.

Thanks for all the feedback.

By the way, RCP, the slip yoke on the front seems in great shape no movement what so ever. Thanks.

The lower gears will definately have an effect on driveline vibes.

Vibes get worse as speed increases, this is just the nature of drivelines. With lower gears, the driveline has to spin faster to achieve the same vehicle speed. Therefore, your driveline thinks you are actually driving faster than before.

For example, when switching from 3.07's to 4.56's, you increase your gear ratio by a factor of roughly 1.5. So if your driveline was spinning at 2000 RPM at 60 MPH with the 3.07's, it would now spin at about 3000 RPM (2000 RPM x 1.5) at 60 MPH! Big, big difference in the vibes.

Just something to ponder when trying to pinpoint your problems.

Jared

Deadeye is right but......with bigger tires you pretty much equal it out. If you go from 3.07's and 235/75's to 4.56's and 33's I think the RPM will stay close to the same.

Matt, you have a very good point, but your figures are not quite right. Circumference is a linear function (pi * diameter), so a tire that is twice as tall will have twice the circumference. 235's are about 29" tall. To go from 3.07's to 4.56's, as mentioned above, you will increase your gear ratio by a factor of roughly 1.5. To keep driveline speed equal, you would need a tire roughly 1.5 times the original diameter.

So 235/75R15's would gear you the same at 3.07s as about 44" Boggers at 4.56's.

Just some food for thought...

Jared

Thanks guys, I wasn't considering those facts... makes sense.

I would also check the CV center bearings. These things dry up and go south as along as your in there. I'm about 6.5", have adjustable control arms. Rusty's Crossmember with 1" drop and a SYE Kit. I ran into some vibes over the winter months. Removed the driveshaft, no vibes. Replaced the axles side ujoint, still had vibes. So I went and replace the two other ujoints and the CV centering kit. No problems after that. Juice

RCP Phx said:

...Also the trans "drop kit" makes the front angles worse...

Click to expand...

Sorry RCP, I have to disagree with you on that one. The front driveline is a dual cardan shaft, which I am sure you know. Yes, dropping the tcase points the front output shaft up like 2* or less. But, that end of the driveline is the dual cardan end. The dual joint should not be significantly affected by this change. The axle end, however can benefit some from the drop.

Ideally, the front joint should be at a 0* angle. If it were a rear driveline you would just point the pinion up with some shims. With the caster to worry about, you have to compromise, of course. The greater angle the front joint is at, the greater the vibes will be, so a drop is pure good idea from a driveline perspective - unless of course you have a bazillion inch lift and the aforementioned 2* or less of increased angle in the dual cardan joint will make it bind. But that is not the case at hand.

I don't recommend the drop for trail use, the lack of clearance sucks. That being said, I have a 1"drop on my rig. Hopefully, I can afford a SYE someday to eliminate the need for this.

I guess I didn't give a solution at all. Just mentioned some of the pros and cons of both paths. Good luck.

Jared

Some of what you said is correct,but you have to look at the big picture and do the math.When I went to 5" I started binding my front Cv joint(I unfortunately have a LP30),so Ive been thru this!The amount of "angle" change with a drop kit is easy to measure.The actual drop "front and back" is a little harder.If you drop the mount by 1",the centerline point of the rear is about 1 1/2" lower,while the front only drops about 1/2".As I always say I paid to much for my lift to give it up,"Fix the real problem"!