Land Rover Discovery Suspensions: Caster

[Mike_rupp]

I'd bet that a double double is much heavier than a LWB shaft. Correct me if I'm wrong, but a LWB rear has ujoints at each end. Assuming that's the case, its only the tube itself that's longer. The tube itself is pretty light compared to a double cardan joint.

My point is that why add mass/weight to the driveline when it doesn't need it? The only reason to use a double double on the front end of a Discovery is to attempt to solve a problem by throwing your hands up and saying "I quit". This assumes, of course, that the vehicle in question has a 3-5" lift. Any higher than that clearly isn't a vehicle used for overland travel.

 

[I Leak Oil]

I would think the forces generated on the pinion bearings by some relatively small, extra weight would be irrelavent compared to the forces the bearings experience during everyday driving. An unbalance shaft of any design might cause undo wear but a properly balanced shaft wouldn't cause any noticable wear. Certainly a DC shaft and it's extra weight is better than the alternative of drive line vibs.
On the lift issue..O.K., I'll bite....
I'm unclear as to how a lift of more than 3 - 5 inches difines what one can use their vehicle for.
Jason T.

 

[Scott Brady]

The arms I installed also correct other problems beyond caster, like fore/aft axle positioning and arm angle. So far, I am very please with the result, ride/drive, zero vibrations and a very strong new driveshaft. The only negative from the arms was (very) slight vibration (due to my nominal lift of 1.5"), which was easily resolved with a double/double Tom Woods driveshaft. I now have a stronger and brand new driveshaft in the front, new ujoints, etc. and a stronger prop-shaft overall. With a taller lift, some of the other suggestions may be more appropriate, but based on my configuration, the Inland Rover arms and TW prop-shaft served my needs the best.

I have a front and rear ARB on the shelf to install next, once I resolve which axle shafts to use. That will be sometime after Central America.

 

[michaelgroves]

The arms I installed also correct other problems beyond caster, like fore/aft axle positioning and arm angle. So far, I am very please with the result, ride/drive, zero vibrations and a very strong new driveshaft. The only negative from the arms was (very) slight vibration (due to my nominal lift of 1.5"), which was easily resolved with a double/double Tom Woods driveshaft. I now have a stronger and brand new driveshaft in the front, new ujoints, etc. and a stronger prop-shaft overall. With a taller lift, some of the other suggestions may be more appropriate, but based on my configuration, the Inland Rover arms and TW prop-shaft served my needs the best.

That seems sensible to me - I think that castor angle correction aside, the advantages offered by a DDC propshaft would more than offset any additional weight.

I have a front and rear ARB on the shelf to install next, once I resolve which axle shafts to use. That will be sometime after Central America.

Nice try, pulling the conversation back on topic

 

[Mike_rupp]

Jason, I don't want to nitpick, but I'm not discussing the weight disadvantages of a DC driveshaft, but a DDC (double double cardan). Why would you add weight to the driveline when you can completely eliminate vibrations by aligning the pinion with the driveshaft using a DC driveshaft, not a DDC shaft?

Do you own a Discovery? Have you ever seen a Discovery with more than 5" of lift? There aren't too many out there that are and I doubt that they are used for overland travel. There are just too many disadvantages with a lift that tall. Regardless, I brought it up only because I'm not sure what type of other changes to the front end would be needed other than what I discussed earlier.

Scott, I also have radius arms that position the axle forward as well as being offset to eliminate the bind in the bushings. I'm not sure how that factors into the discussion. The pinion angle still needs to be accounted for regardless of all of the other geometry changes. I'm curious why with 1.5" of lift in the front that you needed new radius arms in the first place. With 1.5" of lift the caster isn't significantly affected. It changes, but not enough to warrant new radius arms IMHO. There's good reason why OME springs give 1.5" of lift.

 

[gjackson]

Like Scott I'm no-where near a 5" lift. I'm sitting at 2 - 2.5" and the DC shaft and caster corrected radius arms are doing everything I need. This is on a 110, but running gear at the front is the same as a D1.

I need to look into lockers, but they'll be going on to the Rangie before they go on to the 110. The 110 is heavy enough to take full advantage of 10" of suspension travel and I've never needed a locker.

cheers

 

[Scott Brady]

I'm curious why with 1.5" of lift in the front that you needed new radius arms in the first place.

I have experienced death wobble in a Jeep going down a narrow two lane road with a lot of traffic. Caster has since been a point of concern anytime I lift a coil sprung solid axle vehicle.

The 1.5" of lift was enough to bring caster over 3.5 degrees out (from the measurement before the taller springs. That is significant enough for me to notice.

The double/double removed ALL vibration, so this is even better than a DC with "some" vibration with regards to the pinion seal and bearing. The weight difference for a properly balanced and aligned prop shaft is inconsequential, at least to guys like Tom Wood, and I tend to take guys like Tom pretty much matter of fact.

I now have a suspension that is aligned properly, a driveshaft that solves the vibration, the WB is corrected, the vehicle has additional clearance and can carry the intended load, and the recent steering system upgrades all make the Disco handle exceptionally well - much better than stock. It was probably a $3,000 investment total, but worth every penny on a vehicle I intend to drive for the next decade or longer, and like better than anything new on the lots...

 

[I Leak Oil]

Do you own a Discovery? Have you ever seen a Discovery with more than 5" of lift? There aren't too many out there that are and I doubt that they are used for overland travel. There are just too many disadvantages with a lift that tall. Regardless, I brought it up only because I'm not sure what type of other changes to the front end would be needed other than what I discussed earlier.

Actually I did own a 96' D1 and put over 100K miles on it with no issues other than new brakes at 60K and the usual oil changes. Great truck and I miss it.

I've seen a couple with more than 5", probably not a commercial "kit". I personally wouldn't want a 5" lift, nevermind more, but the technical challenges of building a vehicle doesn't inherently exclude it being used in a certain way provided it's built for that purpose. Then of course you could also get into the discussion about defining "overland travel" but who wants to go there again?!!!

Anyone know what type of lift and lockers are used in the big rovers and cruisers used in Iceland?

Great discussion!

Jason T.

 

[Mike_rupp]

Scott, are you saying that it is not possible to use a standard DC driveshaft on a Discovery without vibrations?

A DDC is used to deal with angle issues at both ends and the DC shaft is used to deal with an angle issue on one end. Did you happen to ask Tom Woods if he would use a DDC if a DC is all that is needed?

Another thing: I've owned my Discovery since 2000 and have been researching various problems associated with these trucks so that I hopefully will have a good grasp of what to expect should a problem arise. I have never heard of death wobble problems being associated with caster. Here are the various issues associated with death wobble (on a Discovery): swivel bearing preload / bad bearings, radius arm bushings, wheel balance, panhard bushings. They all have one thing in common: something loose in the front of the vehicle. I chased down a death wobble problem myself that turned out to be bad swivel pin bearings.

Jason, the reason that I brought 5"+ lifted Discoveries into the discussion is that I'm guessing that there will be much more substantial corrections to the front suspension other than what I recommended: pinion correcting radius arms / dc shaft / drilled swivels. For the vast majority of Discovery owners that will be all that is needed.

 

[Scott Brady]

On the Iceland trucks, the suspension lifts are still pretty small. They compensate with liberal fender cutting and 3"+ body lifts.

 

[michaelgroves]

A DDC is used to deal with angle issues at both ends and the DC shaft is used to deal with an angle issue on one end.

I might be being dense here, but the distinction escapes me - how can there ever be an angle issue at one end and not the other? Isn't it just the severity of the angle that matters?

 

[Scott Brady]

Scott, are you saying that it is not possible to use a standard DC driveshaft on a Discovery without vibrations?

No. Vibration comes as a result of the variability in the three driveshaft angles. The angle at the pinion, the angle of the driveshaft and the angle at the transfer case.

In the case of my Disco, there was a slight vibration at the pinion end, due to the caster correction. Most people would have let it be (it was hardly perceptible). I chose to correct it, and have the benefit of a new (i.e. new u-joints), stronger and shinny driveshaft on my truck now

A DDC is used to deal with angle issues at both ends and the DC shaft is used to deal with an angle issue on one end. Did you happen to ask Tom Woods if he would use a DDC if a DC is all that is needed?

I did not ask Tom that, as I had measured the three angles on the shaft, and we determined a DDC was the best solution. I cannot imagine anyone would use a DDC if all that was needed was a DC. Just like no one would use a DC if all that was needed was a standard shaft.

Another thing: I've owned my Discovery since 2000 and have been researching various problems associated with these trucks so that I hopefully will have a good grasp of what to expect should a problem arise. I have never heard of death wobble problems being associated with caster.

Caster alone* cannot cause death wobble, but death wobble can be eliminated or controlled with proper caster.

*the typical change in caster you would have with a 1.5-4" lift.

Caster is an important alignment variable for good handling, reduced wander and return to center feel. If caster is not correct when a suspension lift is installed, any of the causes of death wobble you describe can result in a violent wobble and possible loss of control. If the truck has proper caster, and the panhard bushings go, or the bearings start to fail, you may get a slight shimmy/wobble or other indications of the component failure, but it will be unlikely for it to develop into a death wobble. Then you just change or adjust the failed component, and you are on your way again, all with a no-death-wobble experience .

IMO caster is important enough to bring it back completely to factory specifications, if not even slightly more relaxed with a taller truck.

Good discussion...

 

[Scott Brady]

Michael,

Here are a few good descriptions:

If there are double compound angles, i.e., your angles match neither of the above conditions, then you use this.

The multiple double cardan drive shaft can be built by us for almost any application. It is used in applications where typical drive shaft geometry cannot be obtained for a more conventional drive shaft and needs to run smoothly at high speeds. Commonly this would be a applications such as a Grand Cherokee or Land Rover front drive shaft where the pinion angle cannot be adjusted without adversely effecting the steering caster. Or any application where you have substantial compound angles (an angle as viewed from both the side and top).

 

[michaelgroves]

Thanks Scott - good diagrams! And yes, I was being thick!

M...

 

[Mike_rupp]

Scott, I know all about ideal driveshaft geometry.

I'm all for getting the caster back to stock specifications. However, we disagree on how to get there. You somehow think its better to use the radius arms to correct the caster. I don't see the logic. In your method, you end up having a heavier driveshaft than what is needed.

Using the radius arms to correct pinion / drilled swivels to correct caster / DC shaft to correct vibrations at the transfer case end just seems to be the most elegant solution. Caster is solved, vibrations are solved, and the driveshaft is lighter than in your method. RTE took the approach that you did when they first got into business, yet when they experimented with drilling the swivels they found a solution that solved all of the problems.

It seems that your method didn't take all of the variables into account at the start. It seems that you bought the radius arms to solve one issue but then had to deal with unintended consequences.