caster is at 8*.... what's up

[slickrock]

yes

BUT

your reported +8 degrees of caster has little or nothing to do with your death wobble. Further expanding upon the great information by Pin Head, death wobble is caused by one or more of the following:
Play in steering components None whats so ever
loose u-bolts Tight
loose shackles/worn spring bushings 55 lbs per fsm, brand new bushings
incorrect toe-in 1/8 in
loose trunion bearings done to FSM
loose wheel bearings again FSM and wheel have no side to side play

With +8 caster and no cut and turn (I am sprung under) it's a wonder your front driveshaft will rotate at all as your pinion must be pointing at the ground.

I am not completely convinced of your measurement. As a double check, remove the DS at the pinion and measure the pinion flange angle from vertical and report back. Without a C&T, this measurement should be the same or very, very close to your caster angle.

 

[FJ40-40]

I would be safe to say that if I put the shims in backwards, I would be closer to 1* than 0* with the stock shackles. IF it sits right at zero, I could always put back the 1" above stock shackles to correct it.

Just a clarification ~~ Adding the 1" shackles will make caster more negative. If you want to use the 1" shackles than I thnk I would just remove the shims.

 

[dgangle]

Where do I start.....

Play in steering components None whats so ever I question this. New tire rod ends, drag link ends, center arm assy and steering box ?
loose u-bolts Tight what torque?
loose shackles/worn spring bushings 55 lbs per fsm, brand new bushings OK
incorrect toe-in 1/8 in are you certain? who verified this and how?
loose trunion bearings done to FSM using a fishscale, what torque did you shim these to? was this measurement taken with or without the felt & rubber wipers attached to the knuckle?
loose wheel bearings again FSM and wheel have no side to side play

With +8 caster and no cut and turn (I am sprung under) This makes no difference, you obviously missed my point entirely it's a wonder your front driveshaft will rotate at all as your pinion must be pointing at the ground....[/QUOTE]

 

[slickrock]

Where do I start.....

Play in steering components None whats so ever I question this. New tire rod ends, drag link ends, center arm assy and steering box ? Seriously, everything is new. Nothing is loose
loose u-bolts Tight what torque? can't remember off my head, but FSM
loose shackles/worn spring bushings 55 lbs per fsm, brand new bushings OK
incorrect toe-in 1/8 in are you certain? who verified this and how? Tape measure set at the same location on the tires front ad back.
loose trunion bearings done to FSM using a fishscale, what torque did you shim these to? was this measurement taken with or without the felt & rubber wipers attached to the knuckle? Yes used fish scale and set it EXACTLY as FSM and it was within specks. I followed the FSM when doing it.
loose wheel bearings again FSM and wheel have no side to side play

With +8 caster and no cut and turn (I am sprung under) This makes no difference, you obviously missed my point entirely it's a wonder your front driveshaft will rotate at all as your pinion must be pointing at the ground it is almost level to the ground right now. I know it should be pointing towards the T-case.

SO you agree to to flip the shims around to get it at 1".

My only question is if I am reading positive or negative correctly. IF the pinion is horizontal it is positive and if it is pointing way past te t-case, it is negative. IF that is the case, I am too much positive.

At this point, I am goign to take them out and post a pick of my angle finder and let you have a look at it witout ay shims. We'll go from there. Check back tomorrow evening. I wanted to remove a leaf frm my spring pack anyways and forgot to do it when I put in the longer leaf pin.

 

[dgangle]

You have some seriously conflicting information.

If your pinion flange is vertical within a degree or two and the front axle has never been cut and turned, you do not have anywhere near + or - 8 degrees caster. Period.

May I also suggest you read or re-read my above link to understand the definition of positive and negative caster. This is key. I would suggest getting a better handle on this information before you do anything. Don't complicate this with descriptions of position under vehicle, looking this way or that way.

Good luck.

 

[slickrock]

OK. I drew out what my castor would look like on a protractor and studied the link you suggested. You are right. I confused myself. IF you look at the picture below with the arrow, my angle finder points to 8*+ forward of the axle. SO that means (And I am too stupid to see this the first time) that I have too much NEGATIVE caster. SO when I put the shims in the way SOR stated by using stock shackles and 4" lift springs, I made my situation worse and put my tire center line too far behind of the axle.

My plan then it to get a perfect reading of my angle this afternoon. If it is close 8* /9* negative caster, I either can swap the caster shims around (if it is 9*) or I will have to get a new set of 2* shims and put them with the thick side facing the rear of the rig. This should get me someplace around 1-3* Plus caster.

Sound right?

Thanks for all the help. It sometimes takes me a bit to grasp this stuff and visualize it in my head.

 

[dgangle]

With -8 degrees caster, no wonder is drives like crap. I bet crowned and rutted roads are a handful.

I have no idea how you could end up with -8 caster using 4 degree shims with the thick part of the shim facing forward. Something just doesn't add up.

If you remove the 4 degree shims you will now have 8+4=12 negative caster. To get 1 degree positive you would need 8+1+4+13 degree shims. Something is not right here.

If you flip around the 4 degree shims you will now have 8+4+4=16 degrees negative caster. This is getting crazier by the minute.

Your front axle has never been cut and turned, correct?

If it has not, please measure your pinion angle from vertical and report back.

 

[slickrock]

It is a used 60 axle that was on a stock rig. No lift nothing. I'll take some pics today and post them up.

THis is why I am so confused. Yes rutted or crown roads casued the wobble to be worse. With the picture above, if my angle line is forward of the axle, my caster is negative. Sure enough, that is where it was when measured on the knuckle and I confimed it on the 3rd's fins. It seems the logical thing to do is flip shims.

I wanted to have some on hand, but I called Napa, Kragen, and autozone and none of them sell caster shims. Guess I will have to go through SOR.

 

[Trollhole]

SO you have a 60 axle. I was unaware that a 60 axle would just bolt up without new spring perches.

Also I would think the spring geometry on a 60 would be different than a 40.

What I can tell you is there is no way to really tell what angle you have without:

1. having the vehicle on a perfectly flat level surface.

2. Taking a reading off the diff flange or off the knuckle bearing race.

Positive castor means your steering arm should point up more with the addition of + castor.

To me it sounds like you originally had maybe 1 or 2 degrees of + castor, which is fine for stock tires but flat sucks for 35" tires, and you added 4 degrees of negative castor to it. Giving you a overall negative castor. Which would cause death wobble in a vehicle that didn't have all new parts. In any case it would still drive terrible.

 

[slickrock]

I know where your going. I had this problem before the 60 axle was put in. I am beginning to suspect the springs and since they are flipped, threw off my caster.

 

[pb4ugo]

Like trollhole said is the vehicle perfectly level. Check w/a level on the frame. You need the wt of the vehicle on the springs/tires frt and rear.FYI
I just want to make sure we are getting good #.

 

[Pin_Head]

As others have said, negative caster is bad for handle and wheel wobble. Most cars and trucks have positive caster. The only cars with negative caster I am familiar with are late 60s GM land yachts, and they were not known for their handling.

Measure the caster twice off the machined surface of the knuckle housing with the truck parked in the same place and the opposite direction as this will remove any ground effect, like off level parking surface. The true caster will be the average of the two measurements.

Then do a cut and turn so that you can have a good pinion angle and +3 degrees of caster.

 

[Josie'sLandCruiser]

Hi All:

You can purchase custom steel shims from Roger Brown:

4Crawler Offroad Products - Custom Leaf Spring Shims

Good luck! This confusing stuff!!

Alan

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<snip>

I wanted to have some on hand, but I called Napa, Kragen, and autozone and none of them sell caster shims. Guess I will have to go through SOR.

 

[slickrock]

OK first pic is of my 3rd and DL. My pinion angle is `13 degrees down.

Next 2 pictures are of my angle finder on the back of my knuckle on the flat surface between the thin cover and the knuckle itself. The angle shows -6 degrees, not 8 (bit dark last night and didn’t see it well). It is of the driver side front tire. The front of the rig is to the right of the picture.

Closeup

I am thinking that the by flipping the 4” springs, the angle of the springs has messed with my caster. Once I put in the 4* caster shims the correct way, it added to the negative caster instead of cleaning it up.

At this point, I think I should reverse the degree shim and live with 2* negative caster or
1. remove one leaf from the springs to help correct the issue
2. I really don’t want to put the springs in the correct way and decrease my wheel base, but if I must, I must.


I am picking up some stock springs in about a month and plan to do an SOA in the front so I will CnT then. Just have to make it that long.

 

[FJ40-40]

So that's 6* positive caster. Just take out the shims and you should have 2* positive caster and your pinion angle will improve as well.

 

[dgangle]

+6 agreed. I did a C&T on my FJ40 front axle to point the pinion towards the transfercase and set +6 caster. It steers/handles very well.

I say leave it alone and find the real problem of your death wobble. It isn't the caster.

 

[slickrock]

Well, just to see what it would do, I swapped the caster shims around and took out the smallest leaf on my spring pack and brought my caster to +1* (stock) Still had wobble from 40 to 45ish and it leveled out. It is not awful, but annoying.

Before I put in the 60 series axle I flipped my springs and put in the 60 series steering. It handled like a dream until one day I started to get DW out of now where. Found out my knuckle bolts were loose and decided to just bite the bullet and fix it by throwing in a 60 series axle.

It drove fine with no DW until coming back forma wheeling trip.

The only thing left that I can think of to try to fix is tossing the shims completely because the DW was not as bad without them and maybe focusing in on the steering box. I will post a pic tonight of my pitman arm angle. I would like you input on that. Maybe it has a little angle and when things start to get comfortable after tightening everything down, the box may be causing the trouble.

This is killing me.

 

[dgangle]

In case you missed one of the three hundred seventy eight times I have said this, your DW is not due to your indicated +6 degrees of caster measurement.

Good luck with your shotgun approach! I give up.

Over and out.

 

[slickrock]

No I got your point. But if it is better without them in, it makes sense to do that. Does it not?

The only thing left that hasn't been swapped out since I started to get wobble here and there is the box.

If I had this problem before the new axle, the only thing left is the steering box and pitman angle. I will post it tonight. If it is the pitman arm angle, all I would need to do is weld up the bolt holes and re tap them with the box at a different angle. I will also post a pic of my steering geometry. and let you get a look at it.

 

[Ironmanfj45]

This is a very interesting post. I have learned a lot from the experts here on mud durring my lunch breaks. What a great site! Thanks to those that responded I understand this much better than before. I hope you get your issues resolved and the DW goes away.

Cheers,

Jim