IRS Donor Parts

Vehicles:

            In all applications make sure that the diameter of the axle shafts at the splined ends measure 1.2 inches, the differential has 8.8 cast into its top, and that rear disc brakes are present on the donor IRS.  To determine the gear ratio, and whether or not the unit has posi-traction, look at the tag that is attached to one of the differential cover bolts. The first 4 spaces signify the gear ratio and whether or not it has posi-traction.  If the unit has posi-traction, then the second space will have an L in it representing (limited slip), the remaining spaces specify the gear ratio.  For example, 2 L 7 3 means posi-traction with a 2.73:1 gear ratio.  Most people pay a salvage yard between $300-$400 for the donor parts.  Also, Ford Motorsports sells a 15lb. lighter aluminum carrier with gears and posi-traction for around $650.

1989-1997 Thunderbird Supercoupe (All Posi-traction)

1992-1997 Thunderbird V-8 models with rear disc brakes(some posi-traction)

1992-1997 Lincoln Mark VIII (All aluminum carrier, most non-posi-traction)

1989-1992 Mercury Cougar XR-7, supercharged V-6 (All posi-traction)

1993-1997 Mercury Cougar V-8 with rear disc brakes(some posi-traction), after 94 all Cougars were called XR-7’s

Parts needed

·        8.8” carrier, front mounting bushings, and rear mounting hardware.

·        Inner and outer CV-joints (make sure that the measurement at the splined ends near

   the CV joints measures 1.2”)

·        Spindles and attaching hardware

·        Disc brakes with flexible brake lines and mounting brackets

 NON-Thunderbird parts needed

·        Mustang Quad shocks –Aftermarket KYB shocks usually interfere with tires.

·        ½” Lug nuts (T-bird lugs are metric)               

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