Double Cardan Drive Shaft Solutions (1 Viewer)

[Lugboot]

Would a front 60-series DC shaft work to build a front 80-series DC shaft?

 

[NaterGator]

It's not so much the amount of lift but the amount caster correction. If you did no caster correction you could go 6"+ without vibs, it would be a challenge driving it and probably would have death wobble.

Js on a truck with little to no additional weight ends up being at a height where caster plates should be used which then sets up the axle for a DV Shaft.

Js on a heavily weighted truck might get away with Slee's blue bushings and no need for a DC shaft.

LT,

Are the death wobbles induced by positive caster? I know -3* is roughly in spec, but it would seem to me +3* would have the same net effect on steering 'twitchiness' but I could see it causing problems with the high speed 'death wobble'. I'll be the first to admit I don't understand suspension geometry quite like you and christo and the gang

 

[landtank]

LT,

Are the death wobbles induced by positive caster? I know -3* is roughly in spec, but it would seem to me +3* would have the same net effect on steering 'twitchiness' but I could see it causing problems with the high speed 'death wobble'. I'll be the first to admit I don't understand suspension geometry quite like you and christo and the gang

Actually +3* is ideal (spec is +2*~+4*). Most steering issues as death wobble and tracking issues comes from too low a caster. I'm not sure of too high as that's not easily gotten from lifting a truck. But I would imagine you would have increased steering effort and some strange tire wear.

With all the solutions now available it's really a simple task to get your caster in spec.

 

[NaterGator]

Well I am wondering what the harm would be in achieving the same amount of caster in the opposite direction? As I understand it +3 caster means the axis through which the wheels turn left/right is 3* up from the front side of the axle (in other words hypothetical 90* caster would cause the top of the wheel to act like the front)

If there is no death wobble issue, I guess I don't see much of an issue with letting the truck get all the way to -3* caster? Does that make sense? It is like reflecting the original effect across the axis parallel to the road.

Evidently that doesn't work though, I'm just wondering why.

 

[sleeoffroad]

You only need to drill a new set of holes on the output flange. I reused my existing drive shaft and had the drive train shop chop and weld on the 60 series DC joint. It was really easy to do. Just another option.

If you are talking about the transfer case output flange, that will not work without a lot of effort. It uses studs pressed into the flange. You would have to take the transfer case apart to get the flange off, press the studs out and then re-drill.

 

[Bear80]

If you are talking about the transfer case output flange, that will not work without a lot of effort. It uses studs pressed into the flange. You would have to take the transfer case apart to get the flange off, press the studs out and then re-drill.

That's what I assumed, but I'm still waiting to see pictures of exactly what he has done.

 

[Tools R Us]

Well I am wondering what the harm would be in achieving the same amount of caster in the opposite direction? As I understand it +3 caster means the axis through which the wheels turn left/right is 3* up from the front side of the axle (in other words hypothetical 90* caster would cause the top of the wheel to act like the front)

If there is no death wobble issue, I guess I don't see much of an issue with letting the truck get all the way to -3* caster? Does that make sense? It is like reflecting the original effect across the axis parallel to the road.

Evidently that doesn't work though, I'm just wondering why.

Caster angle settings balance steering effort, high speed stability and front end cornering effectiveness. Increasing the amount of positive caster will increase steering effort and straight line tracking, it makes the steering return to center. Negative caster makes the steering want to turn, at high speed it causes what I call "herding sheep", requires constant steering input to keep the truck on a straight track.

Death wobble is the front axle self steering in a short arc, causing a vibration and the steering wheel to jerk back and forth violently. Excessive positive caster is most often the root cause. It's normally started by a bump and/or braking event causing the steering to move from center, the strong return to center effect causes it to overshoot on return, then it has to return again from the other direction, overshoots, repeat and you have death wobble. It can be caused by excessive negative caster, but is more rare and needs to be way out of spec for it to happen.

Death wobble is often associated with or will shortly cause, loose suspension components. A suspension setup that has close to 0 caster is much more tolerant of loose suspension components, softer bushings, etc, more caster requires a tighter setup.

Caster spec varies greatly with suspension, tire, etc, type and setup. In the old days of bias ply tires some cars even called for negative caster, bias ply tires cause some return to center effect and the manufacturer wanted easy steering. Swap to radial tires and the car would be all over the road, add some caster and it’s driving good.

In my experience with the 80, I am most happy with a small amount of positive caster. I have driven it with negative (not recommended), bushing corrected w/OME 2.5” springs and w/J’s. Now it sets at 24.5” hub to flare and on the arms that I made I shot for the most caster possible and overshot for my liking. It requires more steering effort than necessary to hold the steering turned in high speed turns and tends to wobble. Have replaced most of the bushings and know right away when something is even slightly loose. On the new arms I will shoot for about 1 degree of positive caster. Suspension settings are somewhat personal preference, some like “tight” settings, I prefer a somewhat looser setup, just enough to provide stability and turn more easily.

 

[NaterGator]

Tools, thanks man

So to summarize, if I understand you correctly, having negative caster (the steering axis turned slightly down at the front) is what causes the wandering effect at speed, and positive caster (axis turned slightly up at the front) causes the self-centering effect? So a 6" lift, even if it brought the caster to an opposite spec (-3*) would be difficult to drive because of wandering.

Wouldn't you need caster around that mark though to get the right pinion angle for a DC shaft (without cutting and turning everything which would be nigh on impossible)

 

[theyis]

Death wobble is the front axle self steering in a short arc, causing a vibration and the steering wheel to jerk back and forth violently. Excessive positive caster is most often the root cause. It's normally started by a bump and/or braking event causing the steering to move from center, the strong return to center effect causes it to overshoot on return, then it has to return again from the other direction, overshoots, repeat and you have death wobble. It can be caused by excessive negative caster, but is more rare and needs to be way out of spec for it to happen.

Hey Tools,

Are you sure that is right? I have always used my motorcycle to help me understand the geometry and I thought death wobble (or a tank slapper in motorcycle terms) was from close to 0 castor, not too much positive. Take a chopper for instance. Steering is very slow but tracks straight. I don't think I have ever heard of a chopper having a tank slapper. Now take a sport bike like mine with a very steep steering angle. The steering is very quick but t the cost of straight line stability. Ideally, you would run at 0 degrees to make the steering as quick as possible but you can't since you would suffer from tank slappers (or total steering instability) all the time. That's how I understood it but of course I could be completely wrong or maybe there is something else at play so the motorcycle analogy doesn't work well.

Kyon

 

[Lugboot]

I'd like to get back closer to the thread topic and back to my original question about using a front DC shaft from a 60-series to make a front DC shaft for an 80-series. I was reading Bear80's original post again about the differing flange sizes on the front and rear of the 80 and perhaps I answered my own question.

If the 60-series DC shaft will work for a rear 80-series shaft (with mods), then that means it works with the larger flange size in the back of the 80-series. Which also means it probably won't work with the smaller flange size in the front of the 80-series. Any input on this one?

Thanks!

 

[theyis]

Rick beat me, but he is correct. However, in my rear with the amount of lift the pinion is pointed almost dead at the t-case. I could put in upper arm adjusters but after adjusted, even if they are perfectly matched, there will be some vibration and increased wear on the u-joints. The best solution for me is to leave the upper arms alone and make a double cardan shaft. I will acutally come out about the same as the cost of just the upper arm adjusters alone, so it's a no brainer for me.

Dang, forgot to add this to the last reply...

So for my understanding can you clarify? I thought the adjustable upper arms were to make the pinion point at the t-case (i.e. make them longer). There usually isn't a need for the DC shaft in the rear because the shaft is longer and thus less angled at the t-case than the front. Am I thinking right?

Kyon

 

[Bear80]

If the 60-series DC shaft will work for a rear 80-series shaft (with mods), then that means it works with the larger flange size in the back of the 80-series. Which also means it probably won't work with the smaller flange size in the front of the 80-series. Any input on this one.

The 60 series shaft ONLY shares the use of the larger bolts. Since the bolt patterns are different the shaft WILL NOT bolt to either the t-case or pinion.

The ORIGNIAL 80's shaft can be cut and the DC joint from the 60 series added. However, the flange on the t-case must be re-drilled and the studs placed in the new holes. I assume this is what davegonz has done. I would then assume a similar thing can be done to make it work on the front of the 80 series. Actually for this same method a better choice would be to use a DC joint from a '83-'95 mini truck on the front since it uses the smaller bolt sizes.

This IMO this is NOT an ideal meathod. Using the rear shaft of a 4Runner ensures a PERFECT t-case match on the rear of the LC. The whole purpose is to keep this a Toyota BOLT ON solution, although a drive line shop still is involved.

 

[Tools R Us]

Dang, forgot to add this to the last reply...

So for my understanding can you clarify? I thought the adjustable upper arms were to make the pinion point at the t-case (i.e. make them longer). There usually isn't a need for the DC shaft in the rear because the shaft is longer and thus less angled at the t-case than the front. Am I thinking right?

Kyon

With a big lift you will probably need adjustable arms to get proper geometry for ether type of shaft. Mine is 25" hub to flair and the pinion is about half way between pointed at the transfer flange and parallel to it. Also the CV end is effectively longer, so when it's installed the pinion will need to be pointed slightly higher than "pointed at the transfer flange" for correct geometry. Your looking for diff pinion close to the same angle as the drive shaft tube.

To have a CV shaft made you only need the CV end, just have your slip end welded to the other end. This allows buying shafts that are bent, etc, most of the time the yards see then as much less valuable.

 

[theyis]

With a big lift you will probably need adjustable arms to get proper geometry for ether type of shaft. Mine is 25" hub to flair and the pinion is about half way between pointed at the transfer flange and parallel to it. Also the CV end is effectively longer, so when it's installed the pinion will need to be pointed slightly higher than "pointed at the transfer flange" for correct geometry. Your looking for diff pinion close to the same angle as the drive shaft tube.

To have a CV shaft made you only need the CV end, just have your slip end welded to the other end. This allows buying shafts that are bent, etc, most of the time the yards see then as much less valuable.

Okay, that's what I thought. Thanks!

 

[Tools R Us]

Hey Tools,

Are you sure that is right? I have always used my motorcycle to help me understand the geometry and I thought death wobble (or a tank slapper in motorcycle terms) was from close to 0 castor, not too much positive. Take a chopper for instance. Steering is very slow but tracks straight. I don't think I have ever heard of a chopper having a tank slapper. Now take a sport bike like mine with a very steep steering angle. The steering is very quick but t the cost of straight line stability. Ideally, you would run at 0 degrees to make the steering as quick as possible but you can't since you would suffer from tank slappers (or total steering instability) all the time. That's how I understood it but of course I could be completely wrong or maybe there is something else at play so the motorcycle analogy doesn't work well.

Kyon

Motorcycles work a little differently, only one front tire to deal with, less/no linkage, etc.

 

[Lugboot]

The 60 series shaft ONLY shares the use of the larger bolts. Since the bolt patterns are different the shaft WILL NOT bolt to either the t-case or pinion.

The ORIGNIAL 80's shaft can be cut and the DC joint from the 60 series added. However, the flange on the t-case must be re-drilled and the studs placed in the new holes. I assume this is what davegonz has done. I would then assume a similar thing can be done to make it work on the front of the 80 series. Actually for this same method a better choice would be to use a DC joint from a '83-'95 mini truck on the front since it uses the smaller bolt sizes.

This IMO this is NOT an ideal meathod. Using the rear shaft of a 4Runner ensures a PERFECT t-case match on the rear of the LC. The whole purpose is to keep this a Toyota BOLT ON solution, although a drive line shop still is involved.

Thanks much! I have no desire to drill and re-stud the t-case flange. I agree with wanting to go with a bolt-on solution--thanks for putting such a concise thread up with the appropriate driveshafts for the applications.

 

[theyis]

The upper arm adjusters are used to SHORTEN the arms. This will then match the pinion u-joint angle to that of the t-case. However, ANY increase in angle on a u-joint will cause exponentially more wear on the joint and there is still the chance for vibration.

Now when the adjusters are used to lengthen the arms a DC joint is mandatory. If you re-read a few post up my pinion angle with NO adjusters is near zero, so I need a DC shaft.

Okay, I thought I had it. If you were to shorten the arms, wouldn't that force the diff pinion down and away from the t-case? You would want to lengthen them so that the diff would point to the t-case and make the shaft to diff angle straight. Then you would only need to deal with the angle from the shaft to the t-case. I didn't think most people needed a DC shaft on the rear since the driveshaft is longer and the angle is less when compared to the front. Am I messed up here or just not understanding?

 

[Bear80]

Okay, I thought I had it. If you were to shorten the arms, wouldn't that force the diff pinion down and away from the t-case? You would want to lengthen them so that the diff would point to the t-case and make the shaft to diff angle straight. Then you would only need to deal with the angle from the shaft to the t-case. I didn't think most people needed a DC shaft on the rear since the driveshaft is longer and the angle is less when compared to the front. Am I messed up here or just not understanding?

When lift is added, the 4 link causes the axle to move in an arch. This arch makes the pinion point up as the axle moves down. This mean the angle at the t-case is greater than at the pinion. The adjustable arms can be shortened to point the pinion back down to match the angle at the t-case. This is the typical use of the adjusters. After a certian amount of lift, the angles on either u-joint after the arms are adjusted are more than ideal and it will cause increased wear. The best solution in this case is to lenghten the arms and use a DC shaft.

 

[Bear80]

Try and clear some confusion

There is nothing better than pictures to clear things up.

To make a DC front shaft, either the LC's shaft can be cut at the red line and the DC joint from a Tundra or Tacoma added. OR the Tacoma or Tundra shaft can be cut and the yellow area removed to shorten them.

To make a rear DC shaft, the LC's shaft can be cut at the red line and the DC joint from a 4Runner shaft added. Remember the flange at the slip yoke end on the 4Runner shaft will not match the LC's bolt pattern. To keep the 4runner end, a new mutli drilled flang must be put on the LC's diff. These are sold through vendors such as Cruiser Outfitters and made for re-gearing older LC's to work with the new 27 spline pinion gear sets.

The less than ideal way can be to use a DC joint off an 60 series or '83-'95 mini truck/4runner. The flanges on the LC's t-case will then need to be re-drilled and the studs removed.

 

[theyis]

When lift is added, the 4 link causes the axle to move in an arch. This arch makes the pinion point up as the axle moves down. This mean the angle at the t-case is greater than at the pinion. The adjustable arms can be shortened to point the pinion back down to match the angle at the t-case. This is the typical use of the adjusters. After a certian amount of lift, the angles on either u-joint after the arms are adjusted are more than ideal and it will cause increased wear. The best solution in this case is to lenghten the arms and use a DC shaft.

Hey Ben,

Not trying to get into an argument with you here, those are rarely productive, but I think you have your geometry wrong. If you lengthen your upper control arms you may very well solve your rear vibration issue without doing anything to your rear drive shaft. Remember that with the rear 4 link you are dealing with a rectangle (as viewed from the side). As the rear (axle side) of the rectangle moves down, the line formed between the rear points of the control arms stays primarily vertical . That line also happens to be perpendicular to the diff pinion. What that means is that as you lift the vehicle the diff pinion continues, for the most part, to point forward and below the t-case pinion. If you lengthen the upper control arms it will point the diff pinion back up at the t-case. That means you have little pinion angle to deal with at the diff and you have effectively reduced the angle at the t-case as well. So long as your stock drive shaft is in good shape it should be able to cope with the angle unless you are going over 6" of lift. There is only so much angle the shaft can handle, as you pointed out. If you were going over 6" you should still rotate the axle up to zero out the diff pinion angle. Somebody correct me if I'm wrong. It has been a loooong time since I took geometry.