Mark VIII IRS Rear Parts Reuse

[Kpt112]

I have IRS rear from a Lincoln Mark VIII that I planned to use for the IRS installation on my build. I would like to know if you can reuse all the parts from the rear? Another forum member mention that I would need a TrackLok carrier and also the half-shafts and the only parts useable are the differential housing and the uprights. Does that sound right?

My understanding was that if you purchased the FFR IRS option all you would need is the IRS rear from a donor Lincoln or Thunderbird? I am sorry about my ignorance, but what is a Trackloc carrier? I assume the half shafts refer to the spindles from the rear?


Thanks in advance

Kevin

39070

[RickGT40]

Kevin,
What you can use from the Lincoln rear is the center section and the uprights and spindles. The Lincoln has an open differential. Most people recommend rebuilding the rear with a Traction Lock differential, which is Ford's term for limited slip. While the Lincoln differential is a standard Ford 8.8" size, it has spider gears which are unique to IRS differentials so you can't just stick any TracLoc differential in the Lincoln rear. If you are lucky you can find a TracLoc differential from a 90s Thunderbird. The case from the T-bird is steel and weights about 25# more than the Lincoln. otherwise you can get a new aftermarket differential, but you will have to make sure it will work with the IRS axles. (IRS axles are sometimes referred to as half-shafts.) New axles are provided with the FFR IRS kit. You will have to drill new lug bolt holes in the hubs to match the 4.5" bolt circle for the Mustang wheels.

Rick

[Kpt112]

Rick,

Thanks for the information. Very much appreciated.


Kevin,
What you can use from the Lincoln rear is the center section and the uprights and spindles. The Lincoln has an open differential. Most people recommend rebuilding the rear with a Traction Lock differential, which is Ford's term for limited slip. While the Lincoln differential is a standard Ford 8.8" size, it has spider gears which are unique to IRS differentials so you can't just stick any TracLoc differential in the Lincoln rear. If you are lucky you can find a TracLoc differential from a 90s Thunderbird. The case from the T-bird is steel and weights about 25# more than the Lincoln. otherwise you can get a new aftermarket differential, but you will have to make sure it will work with the IRS axles. (IRS axles are sometimes referred to as half-shafts.) New axles are provided with the FFR IRS kit. You will have to drill new lug bolt holes in the hubs to match the 4.5" bolt circle for the Mustang wheels.

Rick

[ArcticAZ]

I went exactly this route a few months ago. Got MK-VIII parts from a local pull-a-part and rebuilt it (myself) with Ford Racing 3.55 gears, all new bearings and seals, and an Auburn "Pro" locker.
The only parts used from the Lincoln donor were housing, pinion flange, hub carriers, and hubs - I had Wilwood brakes, so didn't need those from the donor.

If you elect to do it yourself, you do need a dial indicator, proper torque wrenches, and a case spreader.

AAZ