i have a questions about rear ends. i have a 88 GXL in need of a new rear end (differential) i can get one from a 89 GTU for free. the thing is that the GTU is automatic so is it a LSD one or an open one and the GXL is manual so would there be anything special i would have to do to swap them. any ideas would be helpful

 

The '89 has a viscous LSD as opposed to a clutch pack on the S4's. A manual has 4.10 final drive and the auto has a 3.90 which the difference isn't that significant. Also I believe the '89-91 have different rear diffs and I've heard you can't interchange them without swapping out the axles and what not. And the driveline bolt pattern is different also.

 

ok thanks for the help

 

The 89 GTU did not have LSD.... You can interchnage any N/A diffs fine, but what you have is a 3.90 open diff

 

He is correct. You now have a 4.1 LSD rear end. The one from the automatic S5 will be a open 3.9. It will swap right over no problems, but you would be downgrading.

 

That would be wrong... only the GTUs model, not the GTU model had a LSD for 89.