Yes gears will fit both hemisphere but the difference is with the pinion gear.

You can fit gears of a BW75 (25spline) hemisphere onto a BW78 (28 spline) hemi but you will need to change the bearing on BW75 pinion gear and shim it up 70thou +/- when fitting into a BW78 housing. Otherwise it wont work, to much lash.

If sticking with BW75 hemi and gears into same housing all will fit ok.

I doubt BW78 hemi will fit into a bw75 housing. But Im sure I will be corrected quickley if Im wrong.

Mick

both 3.23 or 3.45 gears found in eseries are found in bw78 series housing.

3.7's are very expensive they sell for twice as much seemingly as say 3.89's i've seen a guy selling new 3.7's on ebay for $450 but i just got a good set of Skyline R34? 3.89's for $120 so for the extra coupla revs i'll accelerating like the clappers in the 5.0 NF when i can afford to get 'em fitted!

yeah 3.7s are pretty rare they are from manual skylines. the auto skyline got the 3.89 and are much more common. 4.11's were found in the 'taras and you can trip over them in the street if you dont watch it. very easy to find. the ones you see for sale are most likely r31 vintage.

ive had 3.89's behind the AU for 1 year, and they are great. a little whiny, but most of that comes from my bad pinion angle after lowering the back end on superlows and not fitting the XR trailing arms to compensate. Highly, highly recomend the 3.89's for their price and performance.

i can get tyre spin off the line flooring it from idle in the dry with new tyres. just plant it, spins for about a second or so as traction gradually comes on. and then Im off.

the diff gears and pacey 4480/2.5 inch are the only performance mods I have and I pulled 2 carlengths from standing start on a VT clubby, and it stayed that way till 120. so Id say a high 6 sec to 100, considering the VT clubby was supposed to do it in 6.6.

it maxes second at about 110kmh, so it basically hits the top of second right on 100, which is perfect.

revs about 2200 rpm at 100 clicks, and 2500 at 110, but my auto is a bit slippy. definately not hard to live with. Overtaking is possible in fourth, no need for kickdown sometimes. its my favourite auto ratio.

sounds like i done good with the 3.89's, looking fwd to seeing peoples faces when the big Fairlane hammers off the line!