Looking to do a front axle flip on a 64 g10

samsvan wrote:Man! I never thought about checking the caster. There are shims in there but they are small. What I'm getting is when the springs compress, the van wants to take off to the left and when they unload, it wants to go to the right. I guess it won't hurt anything to try a bigger shim.
Thanks Don!

What could have been happening here is that the van is choosing any direction except straight and when you fight it to the center, it bumps past and spins wildly towards the other side..... Be sure that when installing the shims that the head of the spring-pack center bolt(S) is(are) still long enough to index into the hole(s) in the axle

I posted a new thread with some pics of my flip in the "between the seats" forum

And now, five years later, I'm having to deal with the bump steer deal.....When I go over a bouncy section, the steering wheel is all but useless....I've got the steering wheel straight while settin still on it's wheels and if I Jack it up at the bumper, the steering wheel turns 190 degrees by the time the wheels are hanging.....
This is neither fun nor acceptable...... designing a cross-steer conversion as we speak...

FOOD FOR THOUGHT

The wild card issue with these diagrams is that the distance from the spring eye to the axle grows a bit when the spring compresses.....
And the reason the drag link geometry can be restored with a dropped axle and can't with a flip is because the steering arm can be bent down to it's original position with a dropped axle but can't with a flipped axle.....
I didn't understand all of this when I started, but it's now painfully real!
Hopefully, my cross-steer will fix the issue!

I'm happy to report that my cross-steer conversion cancelled 100% of my bump steer (well, maybe 99.99%)
It's so nice to not have the steering wheel "shuffling" down the road and the steering wheel remain centered whether I have 125 pounds or zero air in the front shocks...

MORE FOOD FOR THOUGHT...OR SKINNING THE BUMPSTEER CAT PART 2



ADDENDUM 4/28/23: I'M ADDING THIS EDIT AS WELL AS MY NEW FAVORITE EXPRESSION: "JUST WHEN YOU THINK YOU'VE GOT IT ALL FIGURED OUT...YOU HAVEN'T." I STILL HAVE SOME BUMP STEER AFTER ALL THESE DIAGRAMS AND CALCULATION, THE LATTER BEING THE PROBLEM. I'LL ADD A NEW POST TO EXPLAIN. ALL THAT FOLLOWS IN THIS POST IS OTHERWISE FROM THE ORIGINAL, THE 3.5" FALLING SHY OF WHAT'S NEEDED.

It must be a good day for addressing bumpsteer. Congratulations AzDon. Here's what I've done to hopefully solve the same problem, but this time as it relates to a straight axle 4x4 conversion in my 68 GMC Sport Van 108. In both cases (lowering the van via a flipped axle, or an above-the-spring installation of a straight axle), the vertical distance between the ball joints is reduced (dimension d in the above diagram), which results in the drag link arc no longer following that of the spring/axle/ steering arm, thereby causing bumpsteer during suspension cycling. See earlier diagram a couple of posts above this. In this case, when hitting a bump, the spring arc yanks on the draglink which moves the pitman arm rearward, jerking the steering wheel to the right. The driver has a death grip on the wheel to keep this from happening, so the steering arm on the spindle then starts rotating forward to permit the spring and axle to go on their merry way rearward. It is a simultaneous event: the steering wheel jerks right, but the vehicle darts left...a seeming paradox...and scary at speed.

I had removed the stock axle and installed the straight axle, so I couldn't simply measure up from the floor to the center of the two ball joints to determine what "d" was supposed to be. But it was 3" from the spring mounting surface on the stock axle to the center of the steering arm ball joint, and 6.5" on the straight axle (despite my best efforts at heating and bending the steering arm to get it lower, even undermounting the ball joint), still making the steering arm way too high; "d" was thereby 3.5" shy, and the only way I could think of to correct it was by raising the steering box and the related pitman arm ball joint by 3.5".  This obviously puts the gearbox shaft at floor level, and though I looked at the stock gearbox, mine was worn out, and it's a pretty weird unit with the one piece shaft, and it has to sit in a cradle. Summit Racing sells Borgeson boxes and the 920044 unit mounts from the side, permitting a single plate mount with a hole big enough to install and remove the pitman arm along with the box. Amazingly, the pitman arm is straight down in the neutral position, at the perfect tilt for our vans; I run a big rig 20" steering wheel, so I tilted mine a little more toward the dash. See pictures below. Borgeson also supplies the old style Chevy shaft for 55-57s that can be cut down and welded to a coupler, thus fitting our steering wheels, and permitting adjustments to height; since my box is raised, I cut off 4" of the column, which also perfectly fits the gear box housing, tightened down with a two piece shaft collar.

The pictures below show a plywood template, one of many made to get the new box mounted in the right place, the plate simply welding flush on the outer surface of the frame rail. Pretty amazing. The rest is just plating up the cover in reasonable fashion. Despite the side shaft sticking out, my left foot rests to the left of it at the same distance from center as the right. Now, if I can get the rest of this can painted and back on four wheels...six years into what I thought was going to be a two year project.

The pretty little stainless steel shaft collar came in the mail this morning, so I stick these pictures in as well. Under the top plate is an o-ring that gets compressed when the plate is tightened down.

I DID consider that raising the steering box by the same amount that the steering arm had been raised above the leafs MIGHT restore the geometry..... But what if it didn't??....
I wasn't even sure what the critical pivot points were in the leaf/axle arrangement, so I wasn't sure what "arc" to look at and mimic and I wouldn't have been able to figure out how to measure it anyway....
I believed that it was the arc of the actual spindle on the front leaf hanger when I began, but it became apparent that moving the steering arm substantially above the leaf springs had Fubar'd the geometry... Adding to that both arms that the drag link hooks to have arcs of travel, one vertical and one horizontal on an axle that moves vertically...

By abandoning this operational scheme, I was able to use the horizontal bell-crank that is frame-mounted to make the vertical arc of the pitman arm irrelevant and also set the linkage bridging (cross-link) the frame-mounted and axle-mounted arms on an absolutely flat plane between two horizontal arms 39 inches apart, so there would be almost zero measurable arc of travel as the axle moves vertically...

I recently attended a street rod show where 90% of the 30s street rods had cross-steer off of horizontal pittman arms.... Very few had classic side-steer.... I wonder why (?)

And PS......
I'm really happy to see that other fabricators use CAD (cardboard aided design) paper patterns to convert their minds-eye pictures into metal pieces that work....
In my understanding, there are two different scenarios in which the two arcs travel the same path or at least close enough at their centers that bump steer is minimal....

In one scenario, the two travelling lines are the top and bottom lines of a rectangle....This would be representative of a street rod four-link, in which the axle moves straight up and down without "rolling caster" and therefore, not altering the distance from the pittman arm as the suspension moves.... In this scenario the drag link is actually a third line that is the exact length of the top and bottom arms of the 4-link.....

The other scenario is a bit more complicated and is never quite explained mathematically in the diagrams I've seen and is used exclusively where the front axle moves as though it's on a "ladder bar", as in, the axle "rolls caster" as it moves vertically.....
In this scenario, the two lines are the top and bottom lines of a triangle that imaginarily intersect at the pivot end while going straight ahead and follow close to the same arc...It's never really explained in this scenario where the end point of the suspended member (axle assy) arc is being measured at, or whether the lengths of the two lines need to be the same....

As I read up on these, I just became confused by the details I thought were missing and realized that I didn't have the required space to change this geometry on mine anyway...
Raising the steering box would have displaced my clutch pedal, which I had re-purposed as the e-brake and I didn't want to change all of that without the certainty that it would work....

Two other "wild cards" that I couldn't figure out how to calculate are related to the axle, along with it's steering arm being mounted on a leaf spring, which, unlike a ladder bar, grows and contracts as the suspension moves... How is it even possible to plot a reliable arc at a set distance from the pittman arm?...... Also, the axle being mounted above the spring changes the amount and arc of "caster roll" and this also could substantially alter the distance between the steering arm and pittman arm as the suspension travels...I actually believe this is the #1 factor creating bump-steer on a side-steer setup...

Anyway...

I'm really glad to learn that raising the steering box is another workable option for anybody else considering front end remodeling....
If I was going to do the axle flip again from scratch, I'd hang a R&P right on the axle and bring a steering shaft to it with u-joints and a slip-joint....
If I actually was going to do a complete do-over, I'd drop the van over a shortened GM chassis to get full front independent suspension with discs and triangulated four-link with coils in the rear...

As mentioned in the addendum to my post above, I still have some bumpsteer. I had thought that raising the gearbox 3.5" would fix the problem, but although it's much improved, putting the van back on its wheels and tires locks up wheel movement, isolating the steering wheel as the indicator of persisting problems. Despite the change, it definitely jerks right a good 5-10 degrees when jumping on the front bumper and compressing the springs. This compares favorably to the 90 degree swing I was seeing before raising the gearbox, but though close...it's no cigar.

So what's wrong with the plan? I had measured the 6.5 inch height from the spring perch to my steering arm and it's ball joint center on the back side of the axle where the stock steering arm of the Blazer axle just happens to be. However, the stock dropped axle on our vans has the steering arm and ball joint center on the front side. My diagram shows a straight line drag link projection, just clearing the axle, but if you run the orange oval ball joint back along its length to in front of the axle, the upward angle of the draglink causes the 6.5 inches to grow to what looks to be 7.5. I can change things around on my program, and putting that 6.5 in front of the axle results in the same projection angle and drag link length of the stock diagram. Well damn... and duh!!

The bottom line is likely to be this: if you can't help yourself, and you just got to mess with your front suspension the "d" on the diagrams has to be maintained, thereby yielding the stock drag link angle of descent to the steering arm ball joint. In my case I can't change the steering arm and ball joint location because it needs to cross over the axle during its travel for steering. I can't raise, or don't want to raise the gear box any further, so the only way to maintain "d" and get the stock angle of descent is to increase my spring arch and raise the van itself, along with the attached gear box and pitman arm ball joint at "A". The drag link projection angle is then fixed, and the Blazer axle and bent down steering arm / ball joint can stay where it is. Looks like I can't make this work for the desired stock ride height...I had hope to minimize the jacked up look. Oh well...

One last thing to consider: I'm doing all this with a van shell, no engine / transmission, or anything else except the four springs and axles. Loaded up with everything, including six people along for the ride, will compress the springs and decrease the "d" just sitting...so this needs to be figured in, too. Maybe those suspension engineers at GM really knew what they were doing...keep in mind, their design has stood the test of time and was created in the days before computer aided design programs. I'll be penitent for a while, but can hopefully post a success story at some point in the future. All this represents the full extent of my knowledge...maybe it's closer to correct this time

I love thinking about this stuff and discussing the finer points that so cleverly hide from us...

For purposes of this discussion (I'm sure you know that) the factory style drag link steering setup is called "side steer" or "cowl steering" on a street rod.....
What I converted to is called "cross steer".....

What I've basically admitted in previous posts is that I'm unable to come to a mathematical understanding of the arc of movement of an axle placed on a pair of leaf springs and was also unable to plot the angle of travel of a drag link attached to a pittman arm with a vertical arc and a steering arm with a mostly horizontal arc, but that is on an assembly that moves vertically....
I took my cues from the worlds of 4wd, gassers, and street rods and decided to ditch the side steer in favor of cross-steer, which is much easier to understand

So have you considered the possibility of designing a cross-steer setup? It's pretty common in the 4x world..... Your 4x axle's tie-rod is ahead of the axle, right?... And it passes above the leafs or below?
Building a 90 degree bell-crank is pretty straight forward but would likely leave you with too short a drag link.....
There are half a dozen ways to get to your goal, but all of them IMO start with ditching side-steer in favor of cross-steer...

I've got two threads posted in "Between the Seats G" with explanations and pictures...

If you search the H.A.M.B. regarding bump-steer and/or drag link geometry, somebody posted in one of the threads two diagrams from (I think) a Pete and Jakes catalog of the two scenarios that avoid bump steer when setting up a side steer setup......
I'm going to guess that an axle travelling on parallel leafs is more like a wishbone (ladder bar) than a 4-link....
The diagram that correlates shows the drag link and ladder bar line as being very close to intersecting at the swing point of the ladder bar so the two lines are like a triangle swinging from the same location.....I could not figure out how to reconcile that scenario with the stock layout on our vans.....

As far as your bump-steer goes, try this: Mark the steering wheel position with the van settin on it's wheels, then jack the van up by the bumper until the wheels hang and re-check the steering wheel position degrees from the starting point and also note the distance you lifted until the wheels were hanging and which way the wheel went ..... In my case, this test had produced 190 degrees of steering wheel travel in 3 inches of suspension unload and I could have expected an additional amount of bump in the other direction during compression....
If this test only yields 10 degrees of steering wheel travel during 3 inches of unload, it may be impossible to improve it much...

Don, I can tell by your persistence in fixing the bumpsteer in your van, that you are a determined man...going to cross steer was a clever approach to deal with a flipped stock axle, but unfortunately the 4x4 straight axles are front steer due to the drive shaft sticking out the back. I run everything above the spring, which includes the tie rod, but as you surmise, a bell crank wouldn't work up front, so close to the pitman arm. Being of the hardheaded persuasion, I will nevertheless find the sweet spot, most likely by arching the springs to raise the van, which in turn will steepen the drag link's run toward the steering arm ball joint, getting it back to the stock angle. Clearly the green line of spring arc has a lot more horizontal character, more leaned back to the rear, than my diagrams indicated, but the big mistake was in my measurement miscalculation.

I see from your latest post that just popped up, that the 5 or 10 degrees of wheel movement I'm getting might be acceptable. There isn't any going from unloaded to rest; it only jerks to the right on compression (jumping on the bumper), which would seem to indicate the divergence under compression suggested in my very first diagrams a month ago. And it probably would get worse if I could compress the spring until it was straight. For now I'll work on getting the drag link back to the stock angle of descent, and then see what I got. Of note, there is no steering wheel movement when the pitman arm has elevated the ball joint on the right and left extremes, which hopefully indicates that I've only got an inch or two of correction to deal with.

For whatever reason, it's also strange that the standard axle mount point on front springs is way off center, toward the shackles; the closer you mount something toward the shackle the more it's motion becomes horizontal...go figure. Before it's all over, I imagine that I'll have to load the van with sand bags and old engine blocks to make up for the good 1500 pounds that aren't affecting the springs as it currently sits. My little bit of wheel movement means I'm closer, but not solidly in the center of arc overlap; you might even want it to be past center to allow for heavy loads. Much to think about, which unfortunately isn't getting me any closer to finishing the rot repair, much less prepping for paint.

This brings up a question about your van. You have 4 leaves under your axle. Was this the 3/4 ton arrangement in the G20s, or did you get a new set made? A set of Add-A-Springs that I tried a few years back raised the van too much, and made it so stiff that it wouldn't be a comfortable ride. Your front springs look to be more arched than the two-leaf second generation sets that I'm familiar with.

My van was spec'd new with a third leaf and I added some others that are "rough country" jeep parts that I got at the scrap metal yard that are 2.5 wide.... The ride is not harsh....


Something important that's often overlooked when setting up a front bean differential axle is the need to have plenty of caster for directional stability.....Many ignore that when they tilt the pinion for a flatter u-joint angle, they are removing the same number of degrees of positive caster that can only be restored by cutting, rotating, and re-welding the steering knuckles on the ends of the axle tubes....
5 or 10 degrees of bump-steer are probably not going to interrupt straight-ahead travel if you have enough caster....
If your steering moves during compression, I can guarantee that it moves in the other direction as it unloads..... The object is to get as little bump as possible in the center of travel because it's only really an issue while trying to travel straight down the road...

If I was doing 4by on one of these vans, I'd put a rack&pinion right on the front of the axle in place of the tie-rod and run a slip-jointed steering shaft with u-joints out to it from one of those 1:1 90 degree boxes from a Trooper2 or from flaming river.... I'd implement all that before finalizing radiator placement...

Not only is the centering pin substantially closer to the shackle end of the spring, the springs are 3" wide at the ends, but only 2.5" wide at the centering pins!.....

Thinking a bit more about your diagrams, perhaps you should take some measurements and do some modeling of those arcs using scrap metal and plotting them on a piece of plywood to verify them over about 6 inches of vertical travel (3 in each direction from center)

I think the suspension arc would be the front spring hanger to the center of the tie-rod end ball on the steering arm and the length would be on center (straight ahead)....

You'd be looking to minimize any growth or shrinkage in the length of drag link during it's travel in relation to the suspension's arc...

Could I ask to those who find this thread of interest, or at least somewhat amusing, to do me a favor by parking your stock suspension second generation G10 on level ground, with the wheels straight...then getting on your back to measure straight up from the ground to the middle of your pitman arm ball joint, and again straight up to the steering arm ball joint (which is laid on its side and would essentially be the centerline of the draglink at that point), then responding to this thread with the two numbers, so that I can figure what the "d" is in my diagrams for a stock van? I don't think there's much difference with the first generation vans if you want to do that, too, but mention which it is. If you have one of those magnetic stick-on angle finders to measure the draglink angle of drop, that would really be beyond the call of duty. By hook or crook, I will duplicate these numbers into my 4x4 geometry, and see what I got. I was able to bend my steering arm down another half inch, and still get the ball joint to clear the top of the axle yesterday, which cut down my steering wheel movement a tad more...it's got to be getting close. Thanks

PS: AzDon, I much appreciate your input. There's no way to determine these numbers with our much altered suspensions. If there are some responses, it will be interesting to see how consistent these figures are across some stock vans.

I'm really hoping to see someone chime in with the puzzle pieces that solve the bump-steer dilemma.....
If you redo my bump-steer test and look at the difference in drag link distance instead of degrees on the steering wheel, you'd be shocked at how little it takes to result in a lot of travel at the steering wheel....
Don't know if I mentioned anywhere, but the linear travel, lock2lock is only about 5.5 inches from just under 4 turns of the wheel, about 1.375 inches of travel per rotation of the wheel...
So 90 degrees of bump-steer at the wheel is only about 1/3 of an inch of drag-link linear travel...
For reference, mine had 190 degrees in just one direction, so it probably had 3/4" of bump (linear travel of drag link) in each direction over a full six inches of suspension travel.... probably less than an inch total bump steer was making it impossible to control over a bouncy brifge at 45mph...

I continue to scratch my chin, and over the weekend bent up a new steering arm from an off-road unit that's much stouter and had a much more pronounced upward sweep, which helped clear the drag link at full right; the drag link is undermounted to get the ball joint as low as I can get it, just missing the top of the axle during its motion; this helps maximize my "d" measurement, while letting the arm cross over the drag link at full right; the two were just barely nicking each other with the van jacked up and the springs fully extended.

I'll get back to bumpsteer issues, but the above raised a new question to ponder: Since I'm bending my own arm, where's the best location for the steering head / ball joint connection in relation to the axle? There's likely to be only one spot along the draglink "projection" that's perfect, and I don't understand why the stock axle steering arm has the ball joint connection placed in front of the axle by what looks to be 1 1/2 inches. Nevertheless, I bent my arm to match. In my diagrams I drew the pitman arm straight up and down, but when I hooked up my draglink, it was clear that the angle between the pitman and the draglink is 90 degrees, the pitman looking to be at 7 or 8 o'clock in the vertical plane. This makes sense, as it maximizes initial straight line input to the draglink before pitman arm rotation loses efficiency when heading heading past 9 o'clock or 6 o'clock in its rotation...shouldn't the steering arm in its horizontal plane also be in an initial 90 degree relationship with the spindle, thereby having the drag link / ball joint connection directly above the axle centerline? I can't think of any bumpsteer consideration for the stock location, and given my projection theory, "d" is actually reduced, as the ball joint is higher on the drag link projection. In the forward steering arm position, I would think that left hand turns would be slower to initiate and not turn as far for a given amount of wheel input, because the steering arm is on the "inefficient" side of 90 degrees. Lock to lock endpoints on my wheel thereby don't match unless I cheat the system and run the spindle stops at unequal settings. On the other hand, right turns should go like gangbusters, because just as the pitman loses its 90 degree character, the spindle moves into it. Seems to me it would be best to have all motions and endpoints symmetrical by running the pitman and steering arm at 90 degrees on both ends of the draglink. I'll most likely rebend the steering arm to give this a try.

It's actually been sort of fun playing with all this in a perverse sort of fashion, and it's also helped with the bumpsteer issue below. I should mention that I filed out the masters in my pitman arm so that I can make one tooth adjustments in angle; I'll have to weld a mastered head to my 5 inch arm when all gets said and done. I'm also running the 4x4 axle one inch back on the spring to center the larger tires in the wheel well; this means my draglink is one inch longer than stock. And I keep in mind that once the van is back together, my springs and "d" will settle due to the extra weight.

Lastly, the bumpsteer business: It's really close given the raised steering box and revised steering arm, and in fooling with all of the above, plus cutting out some of my floor again, I can see that my 4 1/2 turn lock to lock leaves the pitman arm ball joint a good inch below the floor at full right. I can thereby raise the box another inch if I have to, but continue to hope that there will be some responses to the measurement request so that I know exactly how much I'm off. I also suspect the longer drag link might require more "d" than stock. Otherwise, with the car show season starting, I'll see if someone will let me crawl under their van with a tape measure. I certainly wish I had snapped some pictures and taken some measurements on mine before starting on what I thought was going to be an easy 4x4 conversion. Life goes on.

I'll have to re-read a couple of times to fully digest everything here, but one thing that jumps out at me is the drag link barely clearing the top of the axle or the left steering (tie rod) arm...If any of the parts touch that aren't supposed to at any point in suspension travel, that's a fail!.....The drag link does not have to, itself, be straight, but will still plot as straight between the ball ends.....
I'm lost on the subject of eliminating the bump steer from our traditional side steer arrangement, so I'm mostly waiting to learn how you solve it.....
The bump steer issue is most relevant while you are trying to go straight down the road at speed and less relevant while turning, so you want to concentrate on minimizing it most at center.....

I'm learning how difficult it is to compose concise and easily understood technical descriptions and explanations. Sorry for any confusion, but there's no problem with tie rod interference...my latest epistle refers to clearance with the steering arm, which has to arc over the drag link and undermounted ball joint with full right turns. I'm using a SLF-3000 that Summit sells, heating and bending the ball joint end way down to where the ball joint just clears the axle in its front to back motions.

Once I get my wheels in motion today, I'll snap a couple of pictures and add them to this thread. There's also a possible bumpsteer explanation for the front-of-the-axle position of the stock steering arm, if someone tells me their pitman arm has a greater than 90 degree relation with the drag link when the wheels are straight...i.e. hangs closer to the vertical as in my diagrams. Too many cans of worms...a good day to go fishing.

OK...here are some pictures of recent endeavors, mostly showing my primitive working conditions: newly bent steering arm; straight and full right steering arm swing; current drag link angle (anything close to stock?); stance; tire projection (despite narrowing the axles, the front width is still 5" wider than the rear); tire in wheel well 1" back on the spring; interior with big hole for mid-engine; barbecue engine box.



















addendum: figuring out the correct pixel widths for these uploads took a bunch of edits, as each time you got it looking right on the preview, it still showed up too wide on the site copy, losing the edges and needing further reduction. Trial and error all over again.

Pictures look to me like the drag link can hit the axle, tie rod, and/or left steering arm if the left wheel is up during full right lock, but if you've set the left wheel on six inches of blocks and no interference, I'd call it good.....
I got measurements on stock stuff:
1) drag link is exactly 28"
2)Spring hanger bolt to locating pin is 26"
3)Pittman arm appears to be straight vertical at 3" ahead of the spring hanger bolt
4)Steering arm is about 2" above spindle center at the drag-link ball
5) Drag link hole in steer arm is about 1" ahead of the spindle

So 26" +3" -1" =28"
I believe the stock drag link is non-adjustable because changing it's length probably screws the geometry....
I think the critical measurement from a stock van is going to be from the spring hanger bolt to the drag-link ball on the steering arm with the wheels pointing straight.....
I'm not exactly sure what that measurement will indicate and I doubt it will be as easy as just changing the drag link length proportionally (though it might be)...
Another measurement that might have some relevance to plotting the shape and size of the imaginary box would be to measure from the pittman arm drag link ball to the center of the top of the axle.... This would be basically measuring corner2corner, maybe also measuring up from the axle to the ball and from the leaf hanger bolt to the pittman ball......
I really like the idea of a mid-engine 108 4by4 because u-joint angles can be minimized by lowering the engine/trans, which would also move the exhaust manifolds below the frame, resulting in cooler drivetrain and interior temps because of a shallower doghouse and more free airflow around the engine....Another cool thing about a shallower doghouse is that it won't be as tough to wrestle it out over the engine to get it out of the van for access... I made mine in five sections for just that reason...

Any pictures that you intend to post anywhere on the internet should be resized to 640 by 480 in a photo editing program and saved in albums that are all resized pics, eliminating the aggravation when you are trying to publish something...

Pictures can be deceiving, but not to worry...even at full right there's four inches between the tie rod and drag link, 2 under the steering arm, and a 1/4 over the axle as the ball joint passes by, and these are fixed relationships, the rise of the pitman arm to 4 o'clock in the process of a right turn also helping out with the latter. When you think about it, the rise of the working end of the pitman arm in either direction helps maintain the downward angle of the drag link during the left and right steering motions, and thereby reduces the chance of bumpsteer even at the extremes. Which brings us to the pitman arm for one last post before I get back to sandblasting doors and fixing dents. It was good to hear that the pitman is close to vertical, which makes sense in the diagram below, and saves me a misguided trial of putting both ends of the drag link at 90 degrees to the pitman and steering arms. It also explains why the working end of the steering arm is slightly ahead of the axle centerline in the stock arrangement...at least as I see it...



So here goes: With the pitman arm in the vertical position, it's in an "inefficient" relationship with the drag link...not at 90 degrees, as it would be if the arm was aligned with line A; it's shy by the amount of movement in angle X. But in the vertical position, the top line for the "d" measurement is thereby established, and any right or left motion remains symmetrical in terms of motion imparted to the drag link. As well, had the neutral position been on line A, the ball joint and drag link would swing lower in moving to the vertical position, decreasing "d" and making bumpsteer more likely in a right hand turn.

Then there's the matter of a similar situation at the drag link's connection to the steering arm. The angle Y on the diagram reflects that the steering arm is not on the centerline of the axle; it is 1 1/2 inches in front as measured from the ball joint center, and thereby not in a 90 degree relationship with the drag link. This, too, would normally be an inefficient relationship in terms of imparting movement from the drag link to the steering arm, but I would bet that it matches that of angle X at the pitman arm. What happens? Starting from its 6 o'clock position in a right hand turn, the pitman imparts motion to the drag link in shy-of-90 fashion, becoming even less efficient in its motion, while at the same time the steering arm approaches 90, becoming more efficient. One end of the drag link is giving up the ghost, while the other end is regaining it. The exact opposite occurs in left hand turns. In such fashion there is likely to be a much more balanced and sustained feel to steering wheel inputs in going from lock to lock. With a 90 degree relationship at both ends of the drag link, steering would be "gangbusters" initially, quickly petering out and requiring faster wheel input to keep up with both connections going inefficient at the same time. I'm happy to have avoided another experiment in steering arm sculpture.

OK...that's all I can say. I'll stick to my assertion that in altering the relative vertical position of the steering arm to the pitman arm ball joint, by raising or lowering one of our vans with side-steer geometry, the stock "d" has to be reestablished, as well as the drag link's angle of descent, because these two things put the drag link and steering arm in the best location for following the upward and rearward motion of the axle during spring compression. There's no bumpsteer if everything is in the right place. In my case I raised the steering gear box to get "d" back to spec and may go another inch since my van is an unloaded shell on wheels. I'll keep looking at the 29 inch drag link, as my 4x4 conversion resulted in a one inch rearward axle location to center the tires in the wheel openings, but as in my very first diagram, its a matter of parallel movements, and there is a sweet spot where all goes well. It's very close, and I'm almost satisfied...I hope it's just a few more tweaks. Mostly I need to crawl under a stock van and measure the setup, taking a good look at the pitman arm...it all makes sense to me, but my mother always told me I never had any.

For now, it's back to sandblasting the doors and finishing the body work. I've got to get this thing painted and start putting it back together. The moral to the story should be this: unless you are crazy, have decent welding and fabrication skills, and enjoy spending way too much time working on an old van...you should leave well enough alone and instead have fun driving it. Keep fiddling, too!  V. Olins