hi all, ive got my old four speed box back in my datto after my five speed failed. the four speed isnt to bad (although it does whine alot when the car is pullin hard) but i am missing that extra gear. when i do 100-110kph my car is reving at around 4000revs which is loud. i have a borg warner diff from a later model 120y sedan in my car (the local one), i was wondering if there is a diff centre i can get from another car that will slide straight in to my diff which would make my revs lower?

Ah, there's the trouble with the Borg Warner -- it doesn't have a removable "diff center" like the Nissan rears. You have to actually change the entire assembly or the Ring & pinion gears.

yes, but there are more choices with tht e borg warner parts, apparently from diff rebuilders

I had a Detroit Locker installed in a Falcon rear some years back, by a "specialist" gearbox & diff shop.
I watched in horror as he prized the original ring gear & diff from the housing with a tyre iron.

If you have a workshop manual, it shows a special tool that actually spreads the diff housing a few thou to remove the preload on the side bearings so that the center parts can be safely removed, or re-installed, & this was a "specialist"

If you are going to mess with these Warner rear axles, make sure the rebuilder has the ability to do the job properly, or you may just end up paying twice for a shoddy job.

I think i will stay with the Jap diff center.