The 89 and newer MN12 Thunderbirds came with an open 7.5 inch rear end if equipped with the standard V-6 andAOD Super Coupe had an 8.8. The ratio for the 7.5 V-6 was 3:27 to one and the ratio for the super coupe was 3.06. Look for a metal tag on the rear pumpkin and if you see the Letter "L" on the tag it means limited slip. I modified a syandard V-6 with underdrive pully increases commpresstion a conical K&N filter and Ford Motor Sport 1.73 ratio Blue bolt down pedistal mount roller rockers and snapped the pinionfear on my 7.5" 3:27 rear gear. I went to a scrap yard and bought a trasc Lok 3:06 rear end and had 3:55 gears installed and the trac--Lok fully rebuilt also installed a super tough u-jount and beefed the tranny and put a high stall converter with extra fluid capacity and radiator style extra cooler for the trans. Changed to Royal puple fluid and hav had great success since. I have an autogage tach and the Thunderbird is still gaining spreed at 150 Miles Per Hour with the none splip converter and correct gear drive # of teeth for correct speedo reading. Good thing that the Cross drived Rotors up front stop as well as advertized. The traffic travling at 70-75 MPH come up very fast when one is travling at 150 MPH. In any case the stock V-6 AOD had a 7.5" rear end and the Super charged modle had a 8.8" both of course are fully IRS. I do not know what the 5.0 or 4.6 v-8 had . I would inmagine and 8.8 open rear. If you are looking for a 8.8 with Traction Locxk rear end--the best bet is a Super Coupe. If it has over 75,000 miles on it I would plan on having the R&P replaced as the SC owners tended to use the power they had. :)
|