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BOB RYDER . May 20, 2022 . All Feature Vehicles
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Heidts PRO-G IRS 1964 ½-70 Mustang

Back-in-the-day, Mustangs, Camaros, ’Cudas, Challengers, Cougars, Javelins and Firebirds were all competing in the SCCA Trans Am racing series during its golden era, 1966-72. These original domestic pony cars raced on road courses all over the United States and all were equipped with plenty of torque and horsepower, but it was their braking and cornering performance that was disappointing. The Mustang front strut independent suspension and rear straight axle, leaf spring suspension didn’t add up to an ideal handling package.

Let’s accelerate forward to the current age of pro-touring, road racing and autocross. These types of competition, whether racing door to door or against the clock, calls for superior acceleration, braking and handling, they must be equipped with the complete package. Until recently, all rear-wheel drive domestic pony cars had straight axle leaf spring rear suspensions that tended to hamper cornering performance.

Heidts Hot Rod and Muscle Car Parts has designed and developed an independent rear suspension (IRS) system that will dramatically improve the cornering and braking characteristics of the early model 1964 ½ -70 Mustangs. The Heidts Pro-G bolt-in IRS kit delivers true high horsepower cornering and braking performance.

The Heidts IRS comes as a complete kit with everything you need to transform your Mustang into the ultimate apex-hugging canyon carver and autocross cone blazer. Follow along as Pete Wittenberg of Pete’s Rod & Custom in Anaheim, California, installs the Heidts Pro-G IRS on a ’65 Ford Mustang.

1. After removing the factory rear leaf springs, hangers, mounting brackets, bump stops and Ford 9-inch rearend housing, Pete measured 24 inches from the back edge of the frame then positioned the kit’s frame rail saddles over the factory versions. The pre-drilled holes were used as pilot holes. Two of the four bolts were inserted, and the bolts, washers and nuts were secured. The front bolts will be inserted and secured later.
2. The Heidts aluminum 9-inch rear end center section is based on a Ford 9-inch center section. The mounting crossmember was aligned then secured using four ½-inch bolts that were torqued to 75 ft lbs.
3.The center section and crossmember unit was then located into the frame-rail saddle mounting brackets and secured using supplied nuts and bolts.
4. Heidts offers six gear ratios from 3.00 to 4.11 for the third member that comes pre-assembled with posi-unit.
5. The third member was inserted into the Heidts center section and secured using supplied bolts.
6. Axle seals were installed into the rear end housing using an axle bearing/seal tool with a ball-peen hammer to assure the proper installation of the axle.
7. A pair of 31-spline rear stub axles came with bearings already pressed on.
8. The longer shaft was inserted to the passenger side of the center section.
9. The caliper plate/bearing retainer halves with recessed surfaces were faced towards the housing and secured holding the axle bearing in place.
10. The third member pinion support plate was bolted to the third member.
11. Pete inserted the third member pinion support mounting crossmember between the rear frame rail saddles. The front, two bolts, washers and nuts were then secured.
12. The lower control arm was fitted into the third member pinion plate, center section, tie-bar and crossmember and secured.
13. The lower control arm was fitted into the third member pinion plate, center section, tie-bar and crossmember and secured.
14. The rear suspension upright was aligned with the lower control arm then secured with a long bolt, washers and nut. The outer axle bearing, hub was then inserted in the upright and secured. The outer axle bearing, hub was then torqued to 65 ft lbs.
15. The rear suspension upright was aligned with the lower control arm then secured with a long bolt, washers and nut. The outer axle bearing, hub was then inserted in the upright and secured. The outer axle bearing, hub was then torqued to 65 ft lbs.
16. The rear suspension upright was aligned with the lower control arm then secured with a long bolt, washers and nut. The outer axle bearing, hub was then inserted in the upright and secured. The outer axle bearing, hub was then torqued to 65 ft lbs.
17. Pete inserted the pre-assembled CV-joints and axle half-shaft into the upright and hub.
18. After threading the gland nut onto the axle it was tightened using a 1 ½-inch socket.
19. The kit’s standard Wilwood 10.5-inch vented brake rotor and hat was aligned with the third member stub axle and secured.
20. The lower control arm with upright/hub and half-shaft axle assembly was swung up while the inner axle CV-joint was aligned with the Wilwood brake rotor hat and secured. The bolts were torqued to 57 ft lbs.
21. The Wilwood Dynalite four-piston brake caliper was slid onto the rotor and secured to the caliper/bearing retainer mounting plate.
22. The Wilwood Dynalite four-piston brake caliper was slid onto the rotor and secured to the caliper/bearing retainer mounting plate.
23.The upper control link received an adjustable threaded heim in each end. The heims allow up to a ½-inch of camber to be adjusted into the rear suspension when the assembly is complete.
24. After the coil over spring and shock with adjusting valve collar were carefully assembled, the unit was aligned with upper mounting bung and lower control arm mounting bracket and secured.
25. To achieve maximum stability and strength the long rear sub-frame connector brace was mounted to the floor sub-frame and rear frame rail.
26. The lower suspension member was attached to the sub frame connector and to the lower control arm. This will allow added degree of stability to the rear suspension’s angular and longitudinal access.
27. The lower suspension member was attached to the sub frame connector and to the lower control arm. This will allow added degree of stability to the rear suspension’s angular and longitudinal access.
28. The Heidts Pro G Mustang IRS system is complete (front and rear views).
29. The Heidts Pro G Mustang IRS system is complete (front and rear views).

SOURCES

Heidts Hot Rod and Muscle Car Parts
800 Oakwood Road
Lake Zurich, IL 60047
800.841.8188
Heidts.com

Pete’s Rod & Custom
1121 N. Cosby Way, Ste. D
Anaheim, CA 92806
714.632.6991

Heidts Pro-G Mustang
IRS Kit P/N IRM-101

  • Track width 56 ½ inches
  • 9-inch aluminum housing
  • Third member iron posi-unit
  • CV joint half shafts
  • Tubular upper and lower control arms
  • Steel outer uprights
  • Steel-top cross member
  • Frame mounting brackets
  • Front pinion support
  • Forward struts
  • 10.5-inch Wilwood plain rotors
  • Four-piston Wilwood calipers
  • Wilwood cross-drilled, slotted rotors (Mustang IRS Kit P/N IRM-101-S)
  • Billet single adjustable coil-over shocks with chrome springs
  • Positraction

Options

  • Choice of gear ratio
  • Parking brake and cable kit

Plain billet
Coil-over Shocks CR-106

  • Coil-Over Chrome Springs #350 with
  • CB-106 CR-350-11-C, #400 with
  • CB-106 CR-400-11-C, #450 with
  • CB-106 CR-450-11-C

3rd Member Options

  • Positraction 31-spline 3.00 ratio
  • Positraction 31-spline 3.25 ratio
  • Positraction 31-spline 3.50 ratio
  • Positraction 31-spline 3.70 ratio
  • Positraction 31-spline 3.90 ratio
  • Positraction 31-spline 4.11 ratio

Sub-frame Connectors

  • Sub-frame Connectors Coupe RM-102-IRM
  • Sub-frame Connectors Convertible RM-103-IRM

 

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