6th Gear Poster
Join Date: Jun 2003
Location: spring grove, il
I'm not entirely sure about what you're asking, but... Between Mark VIIIs and Thunderbirds/Cougars the entire housing (center section) with gears, diff., etc. inside will interchange with no modifications necessary.
Step 1: Remove center section from Mark VIII
Step 2: Remove center section from Bird/Coug
Step 3: Do nothing to your fancy aluminum Mark differential/gear/housing assembly (assuming you're keeping the lame stock gears), do nothing to your Bird/Coug
Step 4: Bolt Mark center section into Bird/Coug
The side gear questions you have are in reference to the difference between the side gears in a solid axle differential and an irs differential. This will only come into play if you acquire a solid axle differential out of a mustang, etc. A good route to go is to acquire a used Mark differential housing (they're all aluminum), get a trac-lok differential (preferably an irs one, but I run a solid axle one with no issues), get some gears, and assemble and install them in your car. I'm not sure how much weight I shaved off, nothing to get excited about though.
lowered, koni sport adjustables, 4.30 tl in aluminum housing, mark 8 trans, j-mod, 93 mark viii ds, antenna hole=gone, kooks headers 1.75" primaries, 2.5" catless duals, midmount magnaflow, 96-97 sport wheels with 255/50/16 sumitomo HTR Zs, optima in the trunk, new motor...94 mark 6/6/08