just curious if 3rd and 4th gen used the same spline axles, have a rear axle out of a wrecked 2001 v6 with the y87 3.42 gears and limited slip and would like to transfer that setup into the rear axle of my 91rs

 

The axles are different as the 4th gen is wider but the entire assembly is bolt in as stated many many many times in the past

 

As Midias said, the axle housing is wider by almost 2" on each side. Therefore the axle shafts are longer as well. Shafts are NOT interchangeable between 3rd and 4th rear housing.

However, later 3rd gen axle shafts (89?-92) have 28 splines, same as 4th gen. So, the 4th gen carrier (differential / pumpkin) can be loaded into a 3rd gen housing... And your 91 RS should already have 28 spline axle shafts. AFAIK. YMMV.

 

'82 to '89 F bodies had 26 spline axles, but somewhere around '89 or '90 they were upgraded to 28 splines. After that the splines remained the same all the way through '02.

 

Thank you thats what i wanted to know, im not changing out axle just the guts so i can keep my 16" iroc rims, just wanted to make sure when i slid shafts back in that i wouldn't be SOL

 

My only additional $.02... When you take out the existing axle shafts, test fit into the new carrier before stuffing it into the housing, to make really sure there are no surprises during final assembly.