Installing the Heidts Pro-G IRS System in a 67 to 69 F-Body
Mike Aguilar
You can install new shocks and leaf springs. You can install four bar suspensions or ladder bars. However, because you’re dealing with a solid axle on your 67-69 Camaro, you’re never going to get it to handle very well at speed. If you want the full benefit of modern technology in it, you need an independent rear suspension so each side can react to road conditions without affecting the other wheel. Racing Junk is going to take you through the steps to install the Heidts Pro G IRS.
You’re going to need your complete toolbox for this project-wrenches, sockets, extensions, dead blow hammer, etc. You’ll also need a couple bottles of your favorite gear oil and brake fluid. Here’s a list of the rest of what’s needed:
• Jack, jack stands, and wheel blocks for the front wheels
• Lug wrench or impact gun (preferred)
• Line wrenches
• RTV Blue or Black
• Threadlocker Red or Green
• Level
• Mig welder (optional but recommended)
• Wire wheel
• Hack saw (optional)
If you don’t have access to an impact gun and appropriate sockets, this job is going to take you significantly longer than have these tools will take. Park the car on a firm and level surface to do this project. Place jack stands under the frame rails in front of the leaf springs and carefully lower the car onto the stands. The exhaust system from in front of the differential back must be removed to make room for the installation and operation of the Pro G IRS.
There are four bolts that secure the driveshaft to the pinion yoke that have to come out. Tie the driveshaft out of your way or remove it completely. If you remove it completely, remember that your automatic transmission might leak out the tailshaft. The upper shock moiunt nuts can be found either in the trunk or under the rear seat.
In order to drop the rear end housing, you need to disconnect the hydraulic system supplying the brakes. Locate the main brake line from the front and either disconnect it from the diverter block or if the block is mounted to the underside of the car’s body, disconnect the lines to the rear wheels.
After you’re done installing the IRS, you’ll need to install an exhaust system that doesn’t hit it while you’re driving.
You can either cut the bolts that secure the springs in the car or use a wrench and socket to remove them. However, it’s much easier to cut them.
Now that you’ve got everything securing it into the car loose, it’s time to carefully lower the rear end assembly (shocks, leaf springs, differential, and brakes) out of the car. Slowly and carefully let the jack collapse a few inches and then you and a friend both work the leaf springs out of their front pockets and help the shock absorbers come down. Make sure everything is clear and lower the jack the rest of the way. Pull the jack out from under the car and lift the rear end assembly off it and set it aside.
This is an important step to ensure the strength and integrity of the installation.
Don’t lose the Jesus gasket. They aren’t easy to find and are required. Also don’t strip the screws on the adjuster or break the adjuster by tightening the screws too much.
The hub bolts need to run through the outer uprights and then thread into the hubs.
Using a seal installation tool greatly decreases the possibility of damaging the housing and/or seals.
Measure how much the studs are left exposed two or three times before the Threadlocker is able to dry.
The bolts should be installed through the mounting brackets front to rear.
The bolt holes on the front of the saddles will need to be drilled to half inch using the saddles as a template. Use the ½ X 3 ½ inch bolts, washers, and Nylocs. Use washers on both sides, between the bolt heads and the saddles and between the saddles/frame rails and Nylocs. When doing final assembly, use Threadlocker on the threads. Because this kit uses Nyloc bolts, there is no torque spec; just get the bolts tights.
Slide the ½ X 6 ½ inch bolts into the upper shock mount sleeves from the front before lifting the crossmember assembly into place. This is because the floorpan will block this once the crossmember is installed.
Use the small Nyloc nuts and washers to bolt the third member to the housing. There are ten of each. If you’re supplying your own third member, be sure it’s a 31 spline unit as the axle stubs with the kit are 31 spline units.
Use the supplied bolts to secure the pinion support plate to the pinion retainer. For aluminum housings, use the fine thread bolts, while the bolts with the coarse threads are for iron housings.
When installing the axle stubs, be sure to apply lithium grease to both the splines and the area on the stubs where the seal rides. Also remember that the stub with the longer shaft goes in the passenger side.
Rotate the stub axles to get at the Nyloc nuts with a socket and ratchet for tightening.
Light taps with a hammer might be needed to persuade the bolts to go all the way through both sides of the lower control arms.
Make sure you double check the setting and scale in use on the torque wrench before torgueing these bolts.
Don’t Threadlock or tighten the mounting bolts until after the alignment is done at the end of the installation.
Run the long bolts through from front to rear.
There is a tag on the inner CV joint housing with the proper torque spec for the Grade 8 Allen head bolts.
Installing the new brake lines to the calipers prior to installing the calipers will make installing the lines easier. Route the new brake lines to the main line from the front and connect the three using a three-way brass block and connect. Bleed the brakes.
Install the bolts front to rear.
Install the bottom bolts front to rear to match the upper bolts and the control arm bolts.
A Unibit negates the need to drill pilot holes and use multiple bits.
Make sure this end is the adjustable end. The jam nut can be tightened because a caster adjustment shouldn’t be needed.
This has to be the non-adjustable end.
Get the ride height close by measuring from the hub to the fender, but the final adjustment needs to set the lower control arms and axle shafts as close to horizontal as possible.
Make sure the axles are close to horizontal as well as the lower control arms.
This is what the Heidts Pro G Independent Rear Suspension looks like when the installation is complete.
To make the rear alignment as accurate as possible, this measurement/reading should be taken with the weight of the car on the suspension. The wheels should be installed and the car fully lowered onto them. You will have to lift the rear of the car to adjust the camber using the lower control arm adjusters.
