Unisteer Rack & Pinion Test Installation!

Mechanical work continues on the Night Mission Boss 302, and in this round we complete the installation of the Unisteer steering rack.  But first, some history:

Rewinding back to August 4, 2011, a quick mock-up showed we had a lot of work to do to get the Unisteer rack & pinion steering rack to fit the chassis.  A lot more, in fact, than what is indicated in the installation manual.  Fortunately, I have had a considerable amount of time to think about the best approach to this installation along with a few tweaks that I felt were required to make the installation cleaner and for functionality of other systems and adjustments to remain as unaffected as possible.  Things like oil pan clearance, accessibility to lower control arm camber adjustment bolts and cleaner overall appearance were all things I pondered heavily before arriving at some pretty simple modifications to the bracket that solved all of these issues in the least intrusive manner possible.  In fact, I was so happy with the modifications that I plan to pass them along to Unisteer, along with my steering column modifications, in hopes they find the information useful in helping to evolve the product and improve the downstream customer experience for those that decide to make this conversion in the future.  Here’s hoping!

The first order of business was to identify the areas of the chassis that would need to be modified to allow the rack mount to fit properly and to get a good picture of what would be necessary to improve camber bolt adjustment access. This was made considerably easier by removing the rack from the mount and working with the bare mount for all fitting and clearance checks.

First, we marked the rear lower control arm pocket flanges with a marker to show exactly how much material would need to be removed for proper rack mount fit.  This ended up not being as extensive as I had originally estimated and was accomplished rather quickly with the pneumatic cutoff wheel.  After about a half hour of work per side, the rack mount fit snugly into place with little fanfare and the focus could shift to the camber bolt access.  This was a truly welcome relief as I had anticipated a much larger tear-up based on my original assessment.

Camber bolt access was an area that, in fact, required more modification than I had originally envisioned.  The position of the holes provided by Unisteer was too far inboard to allow proper access of tools and range of adjustment.  Fortunately, the hole size was sufficient and I determined a simple elongation of these access holes would give me everything I needed to avoid having to remove the rack assembly when camber adjustment at the lower control arm was required.  So, turning to my trusty paint pen, I roughly sketched out what the new oval access hole needed to look like so I could come back a bit later and formalize the shape when it came time.

Next, the rack mount was removed and the rack assembly installed on it to allow the entire system to be bolted into place to make final evaluations of some aesthetic features and clearance concerns.  The first concern was the driver side lower control arm operates with tight clearances to the end of the rack mount and I didn’t care for the overhang of the flange in relation to the aluminum rack mounting block.  So, I decided to kill two birds with one stone by marking the left vertical edge of the mount to match the rack mount block and thereby add a bit of clearance to the lower control arm.  This would also make the left side match the finish on the right side where the design already was made to nicely match the rack mount block.  Of course, this is a detail that nobody will likely ever see or recognize, but it matters to me that it gets addressed and it made “right.”  At least in my book anyway.

Secondly, there is a strange and unnecessary lump of steel on the passenger side of the mount that serves no purpose other than to restrict starter and header clearance and potentially conflict with certain oil pan designs.  For me, there was the added aspect of symmetry that I try very hard to achieve and/or maintain and this bit could not be left alone (imagine that!).

On the driver side, the rack mount makes a nice gentle curve from the chassis mounting flange, across the engine bay to the lower cross brace section.  While maintaining good looks, this also provides for maximum allowable space to fit headers, power steering hoses, wiring, etc.  However, on the passenger side, the same area of the brace is an awkward, angular appendage that constricts this area for no apparent reason and complicates fitting headers, starter and some oil pans.  Besides all of that, it looks funky and I don’t like it (there’s that symmetry thing again).  The solution was to mark a nice, gentle curve that mimicked the driver side and opened up the area for more component clearance while still maintaining good aesthetics. 

Then, off to the band saw to remove the offending material from both the left side rack mount area and the right side cross brace edge.  Once the cuts were completed, a few minutes with the angle grinder had the shapes much more pleasing and functional.

The final modification that remained was to formalize the size and shape of the camber bolt access holes and cut them out and finish them to shape.  Since the mounting bracket is made of hefty steel plate, I decided to rough out the holes with my oxy/acetylene cutting torch and finish them up with the air grinder and hand files.  The end result were two nicely shaped oval holes that allow full tool access and camber adjustment without the need to remove the rack from the car.  An added bonus was that I discovered the camber adjustment plates can be slipped into place in their rear locations without any drama at all!  Bonus!

Finally, I reassembled the rack assembly to the mount and put everything back into the car for mock-up of the tie rod ends and spindles.  Unisteer supplies two different outer tie rod ends to cover all applications of the Mustang spindles and they are distinguished by either large or small taper ball joint ends with either 7/16” or 1/2” retention nuts.  In the case of the 70 Mustang drum brake spindles I am using, the “large taper” ball joints were a perfect fit. 

One interesting, but minor irregularity was that the rack was marked as centered on the steering shaft but was not centered as it was intended when the paint marks were aligned.  So Ted and I did a quick centering exercise and re-marked the rack for center.  At the same time, we discovered the rack was a snappy 2.6 turns lock-to-lock, so the response from this rack should be very nice when everything is finally locked and loaded.

At this point, I am quite happy with where we are on the rack and pinion fitting and soon we will move to mocking up the modified steering column that was completed quite some time ago.  In the meantime, the next phase of the front suspension mock-up will be to fit the 13” vented front brakes on rebuilt and modified production hubs.  Plenty more to come!

Here is the complete Unisteer rack and pinion assembly included in the kit.  The GM J-Car rack is obviously very compact and tidy compared to the factory Mustang steering system in '70.

The areas that will require trimming are marked with a permanent marker.  In contrast to my first evaluation, there was not as much modification required as I originally estimated.  These small modifications allowed the rack bracket to bolt up as intended.

Although the suspension is far from properly adjusted, you can see how tight the clearance of the left side rack bracket was to the lower control arm.  This will need some attention.

With the rack removed and the bare rack bracket bolted in place, the position and size of the camber bolt adjustment holes can be easily evaluated.  As you can see, the holes are fine on diameter, but need to be elongated a bit to allow maximum adjustability and tool access.

The right side camber bolt access hole will require an identical modification.

Using my trusty paint pen, I roughed out the size of the new opening .

This is a better look at the amount of material I would need to remove to get the required access to the camber adjustment bolts.  The angle of this shot makes the bolt head look terribly off center, but this is just a trick of the lens.

A test-fit of the rack assembly shows the bracket fits the frame nicely and the rack clears the structures with plenty of room.  In this shot you can clearly see the camber bolt hole marks I made to show how the hole would be elongated.

The right side rack assembly fits quite well and clearance here is very adequate.

 

With the rack installed you can see how close the protruding edge of the rack mount bracket gets to the lower control arm.  Besides this, this extra material looks a bit untidy, so the only thing to do will be to trim it up flush while gaining a small bit of clearance at the same time.

And there you have it.  The bracket is now trimmed neatly to the edge of the aluminum rack mounting block and we gained about 1/4" of clearance to the lower control arm.  Not a lot, but it should provide a small clearance margin where before there was virtually none.

Looking at the rack assembly from the front, notice the bracket shape on the left as compared to the right.  The material above the black line drawn on the left bracket edge shows the extra material than is unnecessary, gets in the way of starters, oil pans and potentially headers and disrupts the symmetrical "look" of the part.

A closer look shows the cut line more clearly.

With the bracket edge trimmed and smoothed, the mount takes on a nice, symmetrical shape that is more functional and pleasing to the eye.  Yet another detail that 99% of the people will never pick up on, but make a difference (if only to me).

Here is another look at the cleaned up edge of the bracket from the front.

After rough-cutting the camber adjustment holes with the oxy/acetylene cutting torch, we ground the edges smooth and snuck-up on the final shape with some careful filing.  You can see how much more access this modification provides and how much easier it will be to get tools in there to tighten the fastener and/or change the camber adjustment plate.

The right side camber adjustment bolt opening is also very accessible, even with the rack installed.  We can work with that!