Tom here stopping by from the S197 forum to ask if you guys might know the answer to this...
I am working this summer to upgrade my 7.5" rear end (I know 8.8 is better but costs big $$) to add the t-lock and 3.73 ring & pinion gears. I have been searching for a t-lock at a decent price but the best I can find is about $450 from American Muscle.com (for an auburn LSD).
Today I found a junkyard complete rear axle from an 85 Mustang SVO for $250! Doing a little research I learned that the SVO's had 3.73 gears from the factory and had the Ford traction lock differential (LSD) standard. I'm pretty sure these parts are robust as SVO's didn't get crappy parts. Hell they would probably hold 300HP no problem (I'd only be feeding them about 260-280HP)
So I wondered...hmmm? Could I just take the track lock diff and ring/pinion form this '85 axle and upgrade my 2006 S197 7.5" rear end with the parts (I have a 4.0 v6 car with T-5, open diff & 3.31 gears)? If I can do that it will save me about $400!!
Assuming they bolt up, and I have checked a few websites which show that the part number for the 2006 3.73 gears and the 1985 3.73 gears are the EXACT SAME PART #, so I would assume they would work. The only real question is did the bolt patter on the LSD's change?
Both cars have the 28 spline axles with five lug wheels FYI. So my axles should go right into the '85 LSD (theoretically).
Does anyone know? I would appreciate any advice/experience you guys have.