i have a 1979 grand marquis, recently the rear end ran out of fluid and the differential gears got all mashed, so the car does not drive or reverse, my buddy has a 1985 grand marquis and i was wanting to know if that differntial would fit in the 79? or maybe an old ford truck diff? did ford make these diffs all different?

 

you would have to check the rear code tag on the diff cover... i know most later models then yours were 8.8 rearends... you could just change whole rearend out

 

So would the rear end from the 85 fir the 79?

 

same frame from 1979 thru i think 1990s... rearend should bolt right in... 3rd member might be different story if the 1979 does not have a 8.8 rear