Topic: Spring wedges

[oldjeep]

So, if I do weld new perches on, what would be the side effects with regards to caster?

Same as if you use shims.  The only way to correct the caster is to cut the welds and rotate the knuckles.

[FourbangerYJ]

Wouldn't a front driveshaft with a CV cure the vibe problem? Or if your front DS is a stock one they are not balanced. BH has a point to pulling the front shaft and drive around to see if the vibes go away.
 I would agree that shims are not the right answer.

[jfrabat]

Curious, have you measured your caster?

Do the vibes disappear when running without the front driveshaft?

I have not measured caster with the wedges on; but before I put them on, it was up to specs (I had just aligned the Jeep).  And yes, the vibes do disappear if I take the front DS out (and were significantly reduced when I put the wedges in), so it is defenetly the angle...

Same as if you use shims.  The only way to correct the caster is to cut the welds and rotate the knuckles.

Unfortunately, I think that is a bit out of my possibilities; I have to find someone I would completely trust for this job, and I dont have anyone at this time capable of doing this...

Wouldn't a front driveshaft with a CV cure the vibe problem? Or if your front DS is a stock one they are not balanced. BH has a point to pulling the front shaft and drive around to see if the vibes go away.
 I would agree that shims are not the right answer.

Not necessarily; you would still need to rotate the front DS so that the angle is correct for a CV shaft.  The probem is that currently I have a 5* difference in the angles of my conventional shaft...



If I were to go to a CV shaft, I would need to rotate the front angle a bit more, like this:



And that would defenetly throw off the caster angles...  Meaning I would need to cut and re-weld the knuckles as oldjeep pointed out...

So, some background, in case there might be something here that helps:

When I first installed the lift, the vacuum disconnect was still in the Jeep, so once I fixed the rear angle, there were no more vibes. When I installed the alloy shafts, the vacuum disconnect was lost (on piece shaft is used), and so the front DS now spins all the time, so the vibrations started.  I took the front DS to be balanced, thinking this was the problem, but it turned out the original DS was bent, so I ordered a Woody shaft.  In the mean time, the front shaft stayed off, and no vibes were felt.  When the Tom Woods shaft arrived, I installed it, and although the vibes were much less than before, they were still fairly strong (you would start to feel them at about 30~35 mph).  So I took out the front DS, and the vibes went away.  When I put in the 4* wedges, I reinstalled the front shaft, and the problem was almost gone (now I get some VERY SLIGHT vibrations only at 65 mph).

Could it be that maybe I installed the front springs backward and this is throwing the angles off?  I'm pretty sure I did not, but let me know...

According to the RE Installation Instructions, the double military wrap shoul dgo to the frame, and in this pic you can see that the single wrap is at the shackle...



Anyway, please let me know your opinions, as I defenetly would like to ged rid of all vibes and the wedges (I dont want to kill myself anytime soon due to a failure of my Jeep when I'm driving down the highway - or any other reaso, for that matter!).

Felipe

[jfrabat]

By the way, if I were to take out the shims and weld new perches on with the axle rotated, what would be the worse that can happen as a result of the caster being off? 

My understanding (a limited one at that) is that the tires would wear a bit more, and turning would be a little more difficult (assuming a 5* additional caster), right?

As it is now (with the shims), the effects on steering are negligeable; not so sure on tire wear.  I can probably take the Jeep to be aligned this weekend (I have a 3 year alignment deal, so I can take it as many times as I want over the next year or so) and see where I am at, and make a decision to weld new perches based on that...

[oldjeep]

By the way, if I were to take out the shims and weld new perches on with the axle rotated, what would be the worse that can happen as a result of the caster being off? 

My understanding (a limited one at that) is that the tires would wear a bit more, and turning would be a little more difficult (assuming a 5* additional caster), right?

As it is now (with the shims), the effects on steering are negligeable; not so sure on tire wear.  I can probably take the Jeep to be aligned this weekend (I have a 3 year alignment deal, so I can take it as many times as I want over the next year or so) and see where I am at, and make a decision to weld new perches based on that...

Depends on which way it's screwed up.  You could get twitchy steering or loose the automatic return to center motion.  Also can cause the jeep to not track if you flat tow.  Or you may not notice anything

[jfrabat]

Depends on which way it's screwed up.  You could get twitchy steering or loose the automatic return to center motion.  Also can cause the jeep to not track if you flat tow.  Or you may not notice anything

Well, with the wedges, it is basically not noticeable, so I am thinking about the new perches...  I guess at the very least, they will be safer than the wedges!

[aw12345]

On flat ground put your angle gace on the bottom of the spindle will give you a reasonable indication where caster is at. You really want to keep atleast 2 degrees of positive caster if at all possible. To me that is more important than the driveline angle. Negative caster most likely will cause it to wander all over the road, and the steering will not return, neither is a good thing, on the plus side caster has no effect on tire wear, chamber and toe in is responsible for that

[DodgeMudder]

My first guess is your correcting the wrong end of the shaft vibe issue.  I'm going to guess you put a t-case drop in while you were putting the lift on,  This will help make it so you can get rid of the vibes in the rear, but by lowering the rear of the t-case, it raises the angle of your front out-put and screws up the angles of your front shaft.  I would get rid of the t-case drop, and adjust your rear pinion angle to correct for any vibes you get in the rear, that way your caster angle will remain correct and you can fix the vibes w/o worryong about the steering and you can use shims much safer.  If I'm wrong and you are not useing a t-case drop then just ignore my post.

My $0.02

[jfrabat]

You really want to keep atleast 2 degrees of positive caster if at all possible.

Well, it currently has about 3* of caster, but the book calls for 6.5*.  This picture was before the alignment (caster was not touched, as it called for a wedge to correct the wedge I already had in place):



Now, looking carefully at the driveline (taking advantage of the fact that the Jeep was lifted, as I was in my office wear!), I noticed that the TC itself seems to be a bit tilted, and this could actually be the cause of the problem.

I should point out that I have no TC drop (at least none that I installed or that I can see), but still, it seems the TC is the problem here...

When compared with the frame, the TC is dropped at the rear a bit and lifted at the front.  Of course, this means that to keep the same angle at the front, the axle needs to be rotated up, which could be the cause of my problem.  So the big question is, should the TC be parallel to the frame?  If so, how do I correct it?  Put a spacer where it mounts on the skid plate?

These are pictures of the TC (I took them with the camera phone, so no flash was available; the shadow on the bottom is the frame):





Here are some pics of the front DS (the angle at both sides is now almost the same, but the TC is pointing up in the front, causing the weird angle that you see):





Here is the wedge in place (for the time being):



Let me know if you think I can fix this by putting something under the TC to lift i up a bit so that it gets more parallel with the frame, and if so, what should I use to rise it...

[jfrabat]

My first guess is your correcting the wrong end of the shaft vibe issue.  I'm going to guess you put a t-case drop in while you were putting the lift on,  This will help make it so you can get rid of the vibes in the rear, but by lowering the rear of the t-case, it raises the angle of your front out-put and screws up the angles of your front shaft.  I would get rid of the t-case drop, and adjust your rear pinion angle to correct for any vibes you get in the rear, that way your caster angle will remain correct and you can fix the vibes w/o worryong about the steering and you can use shims much safer.  If I'm wrong and you are not useing a t-case drop then just ignore my post.

My $0.02

I just saw your post after I posted; although there is no TC drop in, I think you are right, it is the TC angle...

[Bounty Hunter]

Do you have a motor mount lift?

[jfrabat]

Do you have a motor mount lift?

Not that I know of...  If it has one (which I doubt), it was installed by the PO.

[neale_rs]

A guy I know had a similar problem and just put in a CV shaft in the front and is now pretty happy with it.

[jfrabat]

A guy I know had a similar problem and just put in a CV shaft in the front and is now pretty happy with it.

And he did not change the angles up front?  I had to rotate my rear axle for the CV shaft, but up front, there is the issue of caster to consider...

[FourbangerYJ]

And he did not change the angles up front?  I had to rotate my rear axle for the CV shaft, but up front, there is the issue of caster to consider...

Also think about having the stock shaft balanced. Could solve your problems.