Yes, this story is about wiggly rearends for Tri-Five Chevys but the reality is Heidts’ Pro-G IRS will fit neatly under many hot rods. Independent rear suspensions aren’t new in our world of modified cars (and trucks); remember the surge of the Jag and Vette IRS back in the ’70s? The acceptance of the IRS for something other than good looks or the dare to-be-different approach has changed. Nowadays rodders appreciate the added value of ride, handling, and braking that’s inherent to an IRS system.

The Heidts Hot Rod & Muscle Car Parts Pro-G package comes complete with proprietary Heidts components, like the centersection, crossmembers, mounting brackets, and hardware while employing some of the top components our industry has with Wilwood disc brakes and Strange Engineering coilover shocks.

The high-quality combination of parts allows the Pro-G to be used with many of the most potent V-8–powered hot rods. The axles are 31-spline, making them plenty meaty enough to handle lots of power. Note there are two different lengths to the stub axles; the longer one installs on the passenger side, making the shorter one intended for the driver side. Since we are on the subject of “careful” make sure to be careful and do not use an impact gun when installing the halfshaft nut; it needs to be tightened to 100 ft-lb. The nut is a “package” of spacer, nut, nut cage, and cotter pin (all supplied). Another caveat, remember to bleed the brakes before taking off on your shakedown cruise. While on the subject of brakes, take note that the rotor adapters attach to the rotors with the shoulder side of the adapters to the flat side of the rotors; use the supplied button-head bolts (apply Loctite red) and lock washers. From here the rotor assembles/CV-joints need be assembled with the recessed side of the rotor assemblies onto the stub axles. You will note the Wilwood calipers attach to the Heidts caliper brackets and there are shims to be used to center the caliper (puck surface) on the rotor. (If you pop for the optional parking brake calipers make sure to install them with the actuating lever point upward.)

Before taking that first cruise make sure to go over the alignment one more time. You will align the camber on the outer uprights using the adjusters. Turn each of the adjusters equal amounts, guaranteeing not to change its alignment. You are looking for 1/2 to 1 degree at ride height; note the halfshafts should be level when making this adjustment. Toe-in is set at 1/16 to 1/8 degree.

It’s at this time that the Strange coilover shocks can be installed. At this time, with the weight of the car on all four corners, adjust the lower spring seats thereby leveling the halfshafts.

Follow along and see an overview of installing the Heidts Pro-G IRS. (Their instructions are much more detailed with how-to steps to follow as well as excellent line drawers showing how the parts line up.) It will become apparent as soon as you are on the road that straight line ride will be noticeably more comfortable over a solid axle rear. Traction, ride, and handling, will all be improved during cornering, making it apparent why IRS is the way to go for a modern hot rod. Enjoy.

Heidts offers a hardware kit that comes with the Pro-G IRS.

Use the supplied bolts to attach the supplied pinion support plate.

You will need a specialty tool, a race, and seal bearing installer to handle the axle seals.

The supplied centersection studs should be installed using Loctite (red) and leave 1-3/8-inch of thread showing.

Again, using Loctite (red) and leaving 7/8-inch thread showing on the studs that will hold the caliper bracket.

The centersection housing bolts to the crossmember with supplied hardware (1/2x2-1/2 inch and torques to 70-75 lb-ft); note there is an axle vent tube hole provided in the crossmember.

It will take a 10mm Allen socket to handle bolting the wheel hub to upright.

The uprights then attach to the lower left and right control arms using the 5/8x10-1/2-inch bolts (provided).

The Heidts IRS comes with Strange adjustable-coilover shocks fitted with 11-inch at 350-pound springs (Tri-Five application). Here the spring is slid into position, spanner nut is installed and tightened, and then the adjustment knob is reinstalled.

There are adjustable Heim ends used throughout and it’s also important to install the supplied alignment spacers.

Wilwood rotors and calipers are used; here Loctite (red) is used to coat the threads on the 3/16-inch Allen bolts that hold the rotor-to-rotor adaptor that attaches to hub (hat).

A “boxing plate” supplied is bolted to the frame utilizing supplied hardware (bolts, flat washers, and Nylok nuts). Holes will need to be drilled.

Once the centersection crossmember is in position you can drop the third member in place (31-spline); studs should already be in place, now you can use the 10 supplied AN flat washers and Nylok nuts.

Some holes had to be drilled.

There will be some measuring to be done, such as this crossmember support and holes drilled but the hardware is supplied.

The lower control arms are held in place with the supplied 5/8-inch bolts, nuts, and washers. Be sure to use washers between the pinion plate and front adjusters; don’t tighten as yet, still need to adjust camber. For now install the arms straight (parallel).

Lower control arm support is now bolted into position.

The supplied caliper brackets utilize the supplied Nylok nuts and washers to hold them in place.

After the caliper bracket and the inboard rotor/hub combo then comes the halfshaft.

Heidts’ own Vaughn West is installing the halfshafts after the brakes are in place.

Upper control arm is a single-bar per side.

Get out your big-boy torque wrench; retainer nut is tightened to 100 ft-lb. Make sure to position spacers, nuts, nut cages, and cotter pins, which are all supplied.

Strange coilover shocks are used along with 350-pound springs and are measured for a ride height of 12 inches (based on a Tri-Five weight).

Inboard the Wilwood disc brake package is reminiscent of the early Jag appearance but the performance is all modern.

Once nestled into position the Heidts Pro-G IRS will give your Tri-Five, or any hot rod, plenty of enhanced ride and handling characteristics, all the while improving the undercarriage appearance.

SOURCE
Heidts Hot Rods and Muscle Cars
111 Kerry Lane
Wauconda
IL  60084
heidts.com