For many custom builds, there are certain components that many feel need to remain true to their heritage. For instance, it’s sacrilegious to some people if you put anything other than a Ford engine in a Ford, a Chevy in a Chevy, and so on. Debates on this topic span forums the world over, often times leading to heated discussions because it’s such a sore subject for some diehards and purists.
But one major component seems to fly under the radar of that diabolical cross-breeding faux pas, and it doesn’t get near the amount of attention as the engine swaps that cross over to the dark side. For our latest build with Moser Engineering, we crossed that threshold with our Control Freak Suspensions four-link kit for a purpose-built rearend that utilized components we felt would be best for the type of driving we do. After all, our goal with Project Track Attack is to get faster at the track, one upgrade at a time.
We’ve done builds with Moser before that were direct replacements, such as our Mopar 8-3/4-inch rearend that replaced our factory original unit with no alterations necessary. This build is the polar opposite, and although our Moser M9 Fabricated rearend is going in a Mopar, the only thing that stays true to Mopar is the wheel bolt pattern.
When we decided to upgrade our suspension to a four-link setup with QA1 double-adjustable coilovers, we took it a step further than just welding on some brackets. Although it took a little bit of back-and-forth shipping to complete the build, this project highlights what Moser Engineering can do for your custom build – by putting together a custom rearend built to your specifications.
Building The Perfect Beast
The goal for this build was to allow us to keep our cruiser attitude for the several thousand miles per year that our Plymouth sees, but also to lay it all on the line when this dual-purpose musclecar transforms into Project Track Attack a few times each year.
As with any car that sees occasional track time, many components need to lean more towards the track time aspect because of the abuse the car sees there. While we didn’t have any particular issues with our Moser-built 8.75 replacement rearend, we had to start from scratch with this unit because we had a few other changes we were making to the overall stance.
We went full bore with this build, having previously mini-tubbed the rear to accommodate 10.5-inch wide Weld Racing wheels and Falken Azenis 315/40R18 tires. The wheels and tires are nearly twice as wide as what originally came on the car. With the added space from mini-tubs, it gave us a little extra room for fat tires, and we needed to narrow the axle housing, too.
None of this happened all at once, as we set up a plan and laid out all of our goals for this custom build with Moser, and made sure that we checked everything twice. The great news is that however custom your project is, Moser Engineering can work with you to achieve your goals, whether it’s a stock replacement or a full custom build that throws out all the stops.
Setting Up The Build
Our first step in the process was to get on the line with Moser Engineering and lay out a plan of attack. We had to give them the details: we needed the unit two inches narrower than the stock width housing, we wanted to add some flexibility and strength with a Ford 9-inch differential, and although the typical Green bearings on our Mopar build weren’t giving us any problems, we decided that it was time to step up to a tapered wheel bearing that was better suited for road racing with the Big Ford (Set 20 Torino) bearing.
We talked with Moser’s Jeff Anderson, and decided that Moser’s fabricated M9 would be a good canvas with which to build our perfect beast of a rearend. While Moser can accommodate a stamped steel housing for that factory look, such as on our Mopar replacement, the fabricated M9 (for Ford 9-inch applications) was going to provide more strength for our open track days.
Anderson said, “Basically the triangulated and geometric shape lends itself to better vectoring of the load forces thru the housing itself as a support structure for the tubes, axles and the center section compared to an OEM, or even aftermarket, stamped housings.”
This was enough to get the process started, so they fabricated the center section, installed the tubes, and sent us the bare housing so we could tack on the suspension brackets and send the unit back to Moser for final welding. Anderson stated that a competent welder could do the finish welding, but it’s recommended to have a jig so that everything can be kept aligned properly.
He went on to explain that fabricated housings tend to use a bulkhead design to lock the axle tubes to the housing and the faceplate that the center section mounts to. “It is nearly impossible to have an accurate and reliably strong bulkhead in a stamped housing and this is the key to the strength in this design,” he said.
It is nearly impossible to have an accurate and reliably strong bulkhead in a stamped housing and this is the key to the strength in this design. -Jeff Anderson, Moser Engineering
Our future plans call for much more power under the hood, and we have already acquired fatter tires in the rear that are going to provide much better traction, so a reinforced housing was part of our plan with this build.
Putting The Pieces Together
Installing coilover shocks and the Control Freak rear suspension kit meant getting completely rid of the leaf springs, and installing brackets and braces that are a part of the Control Freak kit. All of the necessary templates are provided in the kit, and the unique thing about this conversion to a four-link setup is that none of the components mount to the outside of the rear frame rail. That means that there is nothing to get in the way of wider tires, and it opened up an extra couple of inches, making plenty of room for our 12-inch wide Falken tires.
We started by pulling the old suspension entirely, removing the fuel tank, and putting brake lines and fuel lines aside to make room for some cutting and welding of brackets. There are a couple of brackets that need to be removed from the floor to make room for the new Panhard bar included with the kit, and a part of the rear frame rail needs to be trimmed per the template.
The front link bracket is a solid, formed piece that is aligned to the frame rail and perimeter-welded in place. So it was time to break out our Millermatic 252 welder and get to work. We began by prepping the surface to remove dirt and surface rust, and using the bracket as a template and marking the mounting location.
A perimeter weld was necessary; this bracket is what the rear suspension bolts to and it needs to be a strong connection for the forward links. After that, we had to mark and cut the frame rail for the coilover shock supports, which mount directly to the underside of the frame rail. Control Freak includes the brackets and they’re even notched to help line them up to the car.
As any Mopar owner will attest, gear choices and components are not as plentiful, and are not easy to find. We chose the Ford 9-inch because there are several gear ratios available all the way down to a 3.00:1, and rebuild parts/gaskets are plentiful and easy to find. With our past success with the Eaton Truetrac in the Plymouth, it was a no brainer to stick with what works.
There are several advantages to the Truetrac differential, and for a driver/part-time weekend warrior, it’s a great overall choice. There are no wearing parts in the Truetrac, and keeping fluid in the housing will allow the differential to do its job and should last for decades.
It’s very important to note that the Truetrac is a torsion-type differential and relies on friction to function, therefore, friction modifiers and synthetic gear lube is to be avoided. We went with Lucas gear lube, 80W/90 weight, which is fine for a driver like ours.
With the suspension in place, and the rearend assembled, it was ready to go in the car and the only thing that kept us from driving the car was finishing the front suspension (a major component that needed to be completed, installing our Master Power rear disc brake kit, and acquiring a new, longer driveshaft.
We’ll follow up with the front suspension install from Control Freak Suspension, give you a quick update on how we converted our Mopar disc brake conversion to a Ford Torino-style rear brake setup using our Master Power disc brake kit, and explain our decision to reach out to QA1 for a carbon fiber driveshaft.
Take a look at how that rearend and those fat Falken Azenis tires and Weld Wheels look on this 1965 Plymouth, we definitely can’t wait to try this combination out at the track. The Control Freak rear suspension kit is a very well engineered kit that keeps everything inside the frame rails, and gives us added control over the way the car is going to handle. They have kits for Mopar A, B, and E body cars, as well as AMC and some Ford and GM products as well.
Working with Moser Engineering to put this entire package together was a breeze, and everything turned out exactly as we expected, and one call to Moser can get you on your way to a full-custom rearend, from flange to flange, and cover to yoke. Stay tuned for the rest of our suspension update, and finally our real test: out on the track.