Vibration 10-15mph after adding more caster. Why? (1 Viewer)
- Thread starter Surfdc
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I just measured...17.25" // 21.25" so looks almost dead on with what you got. 3" of lift then?
what the next step is to take a reading of the operating angle of the front U-joint on the DC shaft. Ideally it should be 0 degrees but should work up to 1 degree.
here is a thread that might help you.
DC-Shaft pinion check
I've had a few questions about vibrations and whether or not a DC shaft is the solution/problem. So I decided to post up how I evaluate the pinion angle to confirm if the pinion is aligned correctly for a DC shaft to operate without any vibrations. The technical aspect of this is that a DC...
forum.ih8mud.com
Thanks for the advice! I'll do that next and report back.what the next step is to take a reading of the operating angle of the front U-joint on the DC shaft. Ideally it should be 0 degrees but should work up to 1 degree.
here is a thread that might help you.
DC-Shaft pinion check
I've had a few questions about vibrations and whether or not a DC shaft is the solution/problem. So I decided to post up how I evaluate the pinion angle to confirm if the pinion is aligned correctly for a DC shaft to operate without any vibrations. The technical aspect of this is that a DC...
I find this kind of stuff very interesting. Here is my take on it but I am no expert so take it with a grain of salt and alot of this may be a rehashing of already known info. BTW, I run a OME lift and no caster correction, not the most stable at speed but acceptable, no vibes and I don't daily drive it anyway.
The stock suspension geometry does a good job of keeping the u-joint angles happy through the arc of suspension travel. Even with a decent amount of lift they will continue be happy but as we all know, as the amount the lift goes up the amount of positive caster goes down and high speed stability goes away. This is important, because if the stock geometry does a good job of maintaining good angles, when we introduce a change to the front pinion angle with a form of caster correction in an attempt gain stability we are now disrupting the stock driveline geometry and there's a pretty good chance we will introduce a vibration.
Unfortunately, that leaves a bit of a quandary. Do I deal with wandering front end at speed while keeping a (relatively) vibe free front end or do I adjust the caster to give stable feel at highway speed at the expense of a vibe free front end? Its a bit of a catch 22.
There is a way to get our cake and eat it to (good highway manners and no vibes) but its not a simple as just bolting on parts and hoping it will all work out. It may, but more than likely it won't. The solution is caster correction and a DC driveshaft but you cant just install both and suddenly fix all the issues, it takes alot of measuring and setting things up to work. The first thing to know is that whenever there is a working angle in a u-joint, when the part of the shaft before the first u-joint (pinion flange) is spinning at a constant speed the part after the first u-joint(the shaft itself) is now spinning at a inconstant speed, in a ideal world the second u-joint is working at the same angle as the first cancelling out the inconstant speed so the portion after the second u-joint(t-case flange) is now spinning at a constant speed. All a DC driveshaft is is a self supporting/self centering two-piece drive shaft where the secondary small driveshaft(the DC portion) self cancels its own speed oscillations. But for that to work the single joint has to run at essentially no working angle(the pinion has to essentially point right at the front transfer case flange) thusly introducing no rotational oscillations in the long portion of the driveshaft.
The only way to insure for sure that you are setting it up right is to install the lift, measure how much pinion angle change you will need to keep the working angle of the first u-joint the less than 1 degree needed for correct DC driveshaft operation and choose the correct caster correction to achieve it. Fortunately, we have some very good vendors on the forum that have been down the road before and can help you out but even then there are alot of variables within each vehicle that make it tough to tell you that what they have experienced will absolutely work for you, then only way to know for sure is to measure your vehicle yourself.
Once again, I am by no means a expert on the subject and may be missing a core factor but this is how I interpret the facts and my opinions on it, take it for what its worth.
The stock suspension geometry does a good job of keeping the u-joint angles happy through the arc of suspension travel. Even with a decent amount of lift they will continue be happy but as we all know, as the amount the lift goes up the amount of positive caster goes down and high speed stability goes away. This is important, because if the stock geometry does a good job of maintaining good angles, when we introduce a change to the front pinion angle with a form of caster correction in an attempt gain stability we are now disrupting the stock driveline geometry and there's a pretty good chance we will introduce a vibration.
Unfortunately, that leaves a bit of a quandary. Do I deal with wandering front end at speed while keeping a (relatively) vibe free front end or do I adjust the caster to give stable feel at highway speed at the expense of a vibe free front end? Its a bit of a catch 22.
There is a way to get our cake and eat it to (good highway manners and no vibes) but its not a simple as just bolting on parts and hoping it will all work out. It may, but more than likely it won't. The solution is caster correction and a DC driveshaft but you cant just install both and suddenly fix all the issues, it takes alot of measuring and setting things up to work. The first thing to know is that whenever there is a working angle in a u-joint, when the part of the shaft before the first u-joint (pinion flange) is spinning at a constant speed the part after the first u-joint(the shaft itself) is now spinning at a inconstant speed, in a ideal world the second u-joint is working at the same angle as the first cancelling out the inconstant speed so the portion after the second u-joint(t-case flange) is now spinning at a constant speed. All a DC driveshaft is is a self supporting/self centering two-piece drive shaft where the secondary small driveshaft(the DC portion) self cancels its own speed oscillations. But for that to work the single joint has to run at essentially no working angle(the pinion has to essentially point right at the front transfer case flange) thusly introducing no rotational oscillations in the long portion of the driveshaft.
The only way to insure for sure that you are setting it up right is to install the lift, measure how much pinion angle change you will need to keep the working angle of the first u-joint the less than 1 degree needed for correct DC driveshaft operation and choose the correct caster correction to achieve it. Fortunately, we have some very good vendors on the forum that have been down the road before and can help you out but even then there are alot of variables within each vehicle that make it tough to tell you that what they have experienced will absolutely work for you, then only way to know for sure is to measure your vehicle yourself.
Once again, I am by no means a expert on the subject and may be missing a core factor but this is how I interpret the facts and my opinions on it, take it for what its worth.
Delta VS
Supporting Vendor
Another option (but not one for everybody) is a 2wd conversion.
This is a good visual of your description:
It’s all about working within the geometry constraints of the system. Problems arise when people venture out and want something more or different out of the system. When you do that some trucks might respond ok and others won’t. There really is no reason one of our trucks with a 3” lift can’t have its caster within the factory specs and not have a vibration problem. It’s been done hundreds of times.
Delta VS
Supporting Vendor
There, fixed that for you
- Thread starter
- #89
You explained it very well, and the video Delta posted is so good at showing what the front and rear shaft need to be doing if they are stock. If they are a DC, then as landtank pointed out, the front diff end needs to be within 1* and the dc portion of the shaft is bolted to the transfer, not the front diff.
Edit; As I go down this path, I am learning that the higher the lift the more caster is needed, and it seems that around 3" of lift is the the threshold that is too much caster correction is beyond a stock shaft, and either a dc shaft is needed or caster must be reduced.
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my 2.5" plates work for lifts between 2"-3" and my 4" plates work for lifts between 3.5"-4.5". The gap between the two plates was intentional.You explained it very well, and the video Delta posted is so good at showing what the front and rear shaft need to be doing if they are stock. If they are a DC, then as landtank pointed out, the front diff end needs to be within 1* and the dc portion of the shaft is bolted to the transfer, not the front diff.
Edit; As I go down this path, I am learning that the higher the lift the more caster is needed, and it seems that around 3" of lift is the the threshold that is too much caster correction is beyond a stock shaft, and either a dc shaft is needed or caster must be reduced.
- Thread starter
- #91
Ha! You knew this long before I did!
Dave 2000
Not all Land Rovers are useless!
Not going to read the whole thread but I would be cautious with the UJ greasing, it is quite common to see the sliders get an extra dose of grease and then this sets up more vibes, then you start chasing your tail.
Regards
Dave
Regards
Dave
You explained it very well, and the video Delta posted is so good at showing what the front and rear shaft need to be doing if they are stock. If they are a DC, then as landtank pointed out, the front diff end needs to be within 1* and the dc portion of the shaft is bolted to the transfer, not the front diff.
Edit; As I go down this path, I am learning that the higher the lift the more caster is needed, and it seems that around 3" of lift is the the threshold that is too much caster correction is beyond a stock shaft, and either a dc shaft is needed or caster must be reduced.
Sounds about right, I think in the lower lift levels the amount of caster correction needed is relatively small so you are still within the amount u-joint "out of phase" that wont cause a noticeable vibration. I think when you get into the larger caster correction methods required to get caster right with larger lifts you start to run into vibe problems.
As a point of reference, here are the measurement I got after installing my OME 2.5"(3") lift. Obviously, if you were to rotate the front axle to gain caster you would be getting away from ideal as far as the u-joints are concerned but I'm guessing that a small amount(3 degrees or less) won't be so bad as to cause enough vibes to be annoying but when you get into larger amounts (5 degrees or more) you'd run into more annoying vibes.
View attachment 2570340
^^^ This whole thing is what I was getting at by my queries a while back, but I'm not near smert enough to express it.
What happens if you (@lasoundguy) grease the yoke till both ends of the shaft are tight against the pinion flanges? (hydrolocked?) No this isn't recommended by any expert. Just myself who went down this rabbit hole.
Do the vibs go away?
If so....
...then I defer to @dugsgms to explain what's going on.
In my case, it was phase and orientation (thx to @BILT4ME). Nothing more. (FTR, phase and orientation were skewed from factory by the tranny shop after tranny rebuild). And no, greasing to hydrolock? is no longer a regular maintenance item after sortment.
3" OME lift, no caster correction. OEM bushes all around. Vintage '93 u/js on vintage '93 single cardan front shaft.
Yes a smidge wanderous @ highway speeds, but no vibes at all. I'll take the tiny wander over the heinous, metal bat-clashing vibes all day long. Those were brutal sounding.
Final double check...I would expect any vibration appearing after a caster change to be amplified by the number of driveline components that have been r&r'd to original OEM specs.
Ex. - vintage front/rear diff pinions will complain less about a drive shaft angle change resulting from a suspension lift due to the clearance provided by 25+ years of use and regular, 'normie' maintenance.
- Thread starter
- #95
Measured my flange and shaft angles like @landtank recommended. Looks like a difference of 4.3 degrees. Way past the < 1 degree for a dc shaft. But no vibes.
@digitalmarker @lasoundguy
@digitalmarker @lasoundguy
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I’m surprised you don’t feel any vibrations.
- Thread starter
- #97
Should I be worried about that angle?
If I did have vibration what would you suggest? Next step for me was your plates with stock radius arms and bushings. If not that then lower lift and stock arms and caster correction bushings?
vibrations usually happen when the load on the shaft is removed and the shaft starts to vibrate. This is why it's usually a decell situation. I'd watch the pinion seal and t-case output seal closely for oil weep. If thats happening there is likely vibrations that you cant easily detect.
- Thread starter
- #99
I am updating this thread after a weekend trip to the desert, and to help other MUDders because it seems there is a handful of us going thought the same thing.
So it seems I was wrong, the vibrations are back, or are still there. I just hadn’t drove it enough after the changes to the suspension or drove it enough at different speeds to really tell. But there is a sight mmmmmmmmmmmmmmmmm at 45-50 mph, and a similar sensation but more pronounced at 70 mph. I just hadn’t taken it on enough road miles to determine. Landtank was right, in post 95 I show my angles and they are the cause of the vibration.I have too much caster, which has created too much pinion angle. So I have decided to go back down to a 2.5” spring from Dobinsons and a rubber 2.5 degree castor bushing in my stock radius arms, and back to a stock front driveshaft.
I chose this because my goal is articulation not lift height. And I don’t want to do castor plates.
So it seems I was wrong, the vibrations are back, or are still there. I just hadn’t drove it enough after the changes to the suspension or drove it enough at different speeds to really tell. But there is a sight mmmmmmmmmmmmmmmmm at 45-50 mph, and a similar sensation but more pronounced at 70 mph. I just hadn’t taken it on enough road miles to determine. Landtank was right, in post 95 I show my angles and they are the cause of the vibration.
I have too much caster, which has created too much pinion angle. So I have decided to go back down to a 2.5” spring from Dobinsons and a rubber 2.5 degree castor bushing in my stock radius arms, and back to a stock front driveshaft. I chose this because my goal is articulation not lift height. And I don’t want to do castor plates.
- Thread starter
- #100
So just wanted to update this thread as my vibration issues are gone and wanted to let others know my solution:
I have gone back to my original radius arms with new Dobinsons 2.5* rubber offset bushings after trying the delta 4" arms. I also lowered the whole rig by dropping from an Icon 3" lift to a Dobinsons 2.5" lift. (by the way, both of these lifts netted exactly 3" and 2.5" of height)
I went from 3.6* of castor with the Delta arms to 1* with the offset bushings. The difference is noticeable, but not terrible. I think I am used to is because this is how the truck was for the last 10 years with a TJM lift.
I also went back to a stock Toyota front shaft and got rid of the dc shaft.
I now have NO vibrations and the truck is smooth as butter.
HERE IS WHAT I LEARNED:
-if you are going to choose a 3" lift you are rolling the dice. Go with either a 2.5 or lower, or 4" or higher.
-if you choose a 3" just budget for the delta 4" arms or landtank 4" plates because the castor is perfect. And a PART TIME KIT.
I have gone back to my original radius arms with new Dobinsons 2.5* rubber offset bushings after trying the delta 4" arms. I also lowered the whole rig by dropping from an Icon 3" lift to a Dobinsons 2.5" lift. (by the way, both of these lifts netted exactly 3" and 2.5" of height)
I went from 3.6* of castor with the Delta arms to 1* with the offset bushings. The difference is noticeable, but not terrible. I think I am used to is because this is how the truck was for the last 10 years with a TJM lift.
I also went back to a stock Toyota front shaft and got rid of the dc shaft.
I now have NO vibrations and the truck is smooth as butter.
HERE IS WHAT I LEARNED:
-if you are going to choose a 3" lift you are rolling the dice. Go with either a 2.5 or lower, or 4" or higher.
-if you choose a 3" just budget for the delta 4" arms or landtank 4" plates because the castor is perfect. And a PART TIME KIT.
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