Gemini diff replacement ideas

[flyingbrick]

It seems kirk and everyone else have got ya pretty much sorted. In my opinion go be falcon diff- heaps of different ratios to choose from and lsd's are fairly plentiful ( xr6 LSD duffs can be found for $300) they are strong and heaps of aftermarket support in aus for them.

I WAS going to buy billet axles and billet LSD Center as it eliminates any need for fab work( aside from needing stronger shaft within tq tube) HOWEVER the major limitation is availability of different ratios- of which there are zero that fit other than factory gem (and maybe one model of torana but you won't find one)

Ratios are important to me as I only have a two speed trans.

Cars have run 9's on the stock housing and gears. That's pretty fuckin fast

I'm going 9" because it's the cheapest way of getting 31 splines, different ratios and auto locker/LSD units.

Jase on here is using eb(I think) falcon diff and is even retaining the watts link which is cool.

[R100]

When you say a falcon diff are you referring to a bw78 diff or something else. I think a 9" would be an overkill in my application.

[flyingbrick]

I'm talking eb type. BW I think

[KIRK]

according to that commodore site an lsd falcon diff head may fit into that diff you have in your commodore?

[Jase]

bw78 in mine atm, 2 pin lsd from early falcon with 25 spline axles from a vl, 3.23 gears for the glide with 15's may yet go 2.92's,

after I upgrade to a vs centre  I can run billet 31 spline axles with the later carrier.

gears available up to 4.11s (out of 2l vn) and the lsds swap out between breeds I have a 4 pin falcon lsd in my newer carrier from a vt II

[KIRK]

this interests me. jase do you know if the irs lsd bits from like a modern xr6 or xr8 will work in a live axle bw78?

[Jase]

as long as its the later housing it seems as i have vpss diff here as well I test fitted to a vn carrier,

biggest thing with the bw is the whine caused by the pinion crush bush flogging out,

fix is to put a solid one in at the correct depth,

remember also the earlier bw78 carriers are narrower and although the gearsets swap the lsds/heads won't as they got wider from vn onwards exception being vl turbo and v8 which got the wider carrier and also the 2l vn which got the narrower earlier one.

[Jase]

bw78 under a vn how to undo the pinion nut without a rattle gun

[Valiant]

Hey R100.

I've only skim read over your thread so please excuse any reposts.

Borg Warner 78 series has a 7.8" crown wheel, 4spider LSD and the axles are 28 spline like a 9"

I think if you buy an AU XR6 diff it will be 3.45 to 1 with an LSD.

They are long as so you can get them resplined as there is enough meat further the axle to cut a spline back into it.

I had a 3.45 in my Valiant with a W50 and 225/50/15s and it ran at about 2750 rpm at 100 km/h I changed back to a 3.23 and it is about 2500rpm with the same tyres and gearbox.

 

It's still a lot of work if there is a factory LSD option you can get.

[Frosty]

A heap of the Valiant utes ran a BW LSD but they all run cones not plates and ramps so can be a real pain to get tight and are very fussy regarding oil type. Ran one in my XA 351 powered wagon and it was in and out every 20K km's for a re-shim, ended up using a Ford 9" in the end.

Some of the early Holden's (banjo style) ran what was basically a scaled down Ford 9" but can be tough to find now given their age.

The HQ Common Wealth version (4 link) and a lot of the HQ cop cars and utes ran a Salisbury (correct me if I'm wrong but I think they are the same as the Chev 10 bolt) LSD to.

Most of these can be found with ratios between 3.5 and 3.9.

 

Most of the later BW78's will have 3.23 or 2.92 ratio centers but they have major pinion bearing issues the the earlier versions didn't suffer from. Father in laws EA Taxi killed it's first one at under 200K km's and after it's second one at over $1000 each a second hand XD one was modified for half the money and has now done over 300K km's without hassle.

[CUL8R]

http://www.ozgemini.com/forums/tech/viewtopic.php?f=29&t=23642&p=259959 Explained...

[R100]

Heaps of real useful information peeps. Will keep doing my homework but at this stage I'm thinking of going with the BW78 from a VR commy , piazza axels with piazza discs and doing some sort of a 4 link rear retaining the factory coil spring locations. The BW78 I currently have is a non LSD but I'm sure I can find an LSD centre for it.

What are your thoughts ?

[SOHC]

With those borgwarner (tin hat) diffs you can tell at a glance if its an LSD by it having a rubber plug in the hat rather than a hex plug I am told

 

 

 

Just some useless info

[CUL8R]

Do you have a piazza diff/axles? 

 

I know of a complete twincam Piazza down here..

[Valiant]

Buy one that's LSD and has the ratio you want already.

Head, crownwheel and pinion changes can be a pain and expensive.

What spline are the Gemini axles? your 78 will/should be 28 spline.

[Jase]

originals are 23 spline but not a borg diff, they are same as an early commodore run same size drums etc,

if your mate goes with a borg I have some 25 spline aXles already set up with 4x100.

he'd have to use a vl diff though.

4 link without coilovers could be tricky as the spring perches are in front of the diff tube,

unless you use modified commodore lower arms as they have a spring perch built in

[KIRK]

I reckon most cost effective way to do it would be to do what zep did(hilux diff) but with one of those bw falcon lsd rear ends off trademe:

edit: is it worth the cost/hassle of 4 linking a road going gemini? zeps one seems to go ok with the ladder bar etc

 

 

The rear has been converted to XE Falcon discs, re-drilled to 4x100. I'm running 15" +40 rims and they fit fine. No shortening was needed on the diff and with this brake setup and diff it is only 10mm wider on each side so everything sits in snug.

 

 this looks ok value, just been rebuilt etc:

 

http://www.trademe.co.nz/motors/car-parts-accessories/ford/diffs-axles/auction-613048312.htm

 

I think its a Salisbury diff?

[flyingbrick]

Definitely go ladder bar. Much less work when you can forget about making room and mounts for top links

PLUS

from all research I've done for my vehicle you can gain sweet F all going four link done well and LOSE badly when it's setup wrong.

[R100]

Cheers heaps for all the info. Lots of good knowledge on this thread from those of you who have done this sort of thing befor. Because my gemini has been sold to a friend, he has different ideas of what he wants from the vehicle than i did.

He also has a lot to learn about what can and cant be done. 

He also has been conducting his own research, joining ozgemini and searching the interweb. 

 

We are gathering ideas and i will talk to Lee at diffs r us next week to get his ideas.

 

The gems new owner wants to turbo it, mini tub it, 15x10" on the rear, Use it as a street car and take it to the track. He has deeper pockets than i do. Will be interesting to see its progress over the next couple of months.

Im trying to talk him into 15x7 or 15x8" on the rear with 185-55 or 195-50's  as i do not see much benefit in going wider other than the wow factor. Money is better off being spent on other things. 

 

All the engineering work, diff replacement will be carried out by The Steel Surgeon in Manukau. 

 

When it comes to diffs im a 9" man or Hilux/ Hiace. Having had 8 or 9 diff conversions done in the past using only these. 

But the gem is so small and light. It will break traction long befor anythings going to snap. 

 

BW78 is the route im looking at for the Gem. But maybe be better off finding one with an LSD head allready fitted. The 3.08 ratio sounds like a good starting point also.

Nothing in concret yet though.