 Differential and rearend in 1969 Mach I?
Hey fellas,
After checking my rear diff fluid in my 1969 Mach I 351W, auto FMX, I found that it was reduced to almost-grease. Time to change the "yummy lube" (as I call it since it smells like CRAP!)
After going to advance auto parts online, I found that there were three or so rear diff gaskets I could purchase that came up with a 1969 351 M-code mustang (there was no designation for mach I). There was a 7 1/4" ring gear 8 hole gasket, 9" ring gear 10 hole, and an 8" ring gear 10 hole gasket. What is the appropriate gasket for my vehicle, as I tried to count the bolts on the rear diff cover, and there isn't one as on many modern vehicles. THe gasket looks like it would be placed on the side of the differential closer to the front of the car--will I have to unbolt my driveshaft for this?
P.S. Does anyone know how I can calculate a top speed given certain transmission and rearend gearing, given horsepower and RPMs, as I am considering changing my rearend gears for more low end pep but don't want to redline the thing at 65 mph. Thanks a bunch, guys!
__________________ My other toy is a '69 Mach I
351W, .060 over, heavy exhaust cam, straight pipes--approx. 325rwhp | 
