My diff conversion

[amgis_obrut]

ok had a bit of a brain fart and decided to cut down a BW 78 ford diff to fit into a GH sigma in preparation for my Cleveland conversion

Its not 100% complete so i'll up date once complete

THE DIFF>

I started with a 3.45:1 LSD 28 spline borgwarner that i removed from an Ford EF Fairmont Ghia, this diff is 1545mm from wheel mounting face to wheel mounting face



First thing was to strip the diff and remove the ford brackets



Once the housing was stripped it was time to figure out how much needed to be removed so it would fit the sigma right, the factory sigma diff is 1388mm wide but seeing as im using a ford wheel that has a +10 offset i couldnt go the same length as the sigma diff as it set the wheels out to far

I chose to go with a total width of 1355mm which meant i had to remove 190mm (95mm each side) from the ford housing this worked out to be a blessing in disguise as the ford axles differ in length by 95mm meaning I could use the short axle for the long side and have the long axle cut down 190mm splined and slotted in the short side

Before i cut the housing i scribed a line along the axle tube so a could re-align the ends in their correct position



THE JIG>

Once the housing was cut i needed a way to make sure it was going to be straight once welded back together, So i had a look on the net at how the pro's do it and found they use a housing bar, basically its a stiff bar that passes through collars that replace the bearings and in turn keeps the housing in line

Collars, the two larger collars go in the center the smaller fit in the axle tubes



Collars on bar











A nice deep V ground into the join to provide a nice deep strong welded join, tacked in place with a mig all final welding will be done with a tig



Cut and splined short side axle



Diff dummy assembled to check measurements and to make sure it all works before final welding




Next thing to do is make another jig to help align the suspension arm mounts

[astronturbo77]

good on ya mate, good to see someone doing things properly and not just talking about diff conversions

[rob020]

wow, so that is roughly how much work went into my diff?? whoda thunk it?
glad i didnt have to do it, i cant weld for shit...

cheers,
rob

[stealth]

yeah theres a shitload of work involved in shortening any diff that why diff shops charge so much!
hay mick did you fit some sleeves internallly to support the tubes ,if not will a engineer in nsw pass that?
i only ask as thats a big no no up here in qld ,we have the do it the hard way and pick the tube out of the centre ,shorten it then reinsert and weld ,not to mention your relying purely on the weld to hold your car up
as i said in qld no engineer would let that go out with there name on it
that said im sure it will hold and you wont have to many drama's as long as your good with the tig and do the weld sequence correctly
(mate im not have a go just giving a opinion please dont take it the wrong way ,at least your doing something)
cheers stealth

[Superscan811]

Speaking as a novice, I would have internally sleeved the tubes and but welded the ends to it.

ie: something like this.



Just a thought.

Cheers.

EDIT: Just modified the pic to better show what I meant. RED is existing tubes, BLACK is internal sleeve.

[amgis_obrut]

no worries stealth

theres no internal tube its not a feasible option as the housings are usually bent from the factory when they weld the brackets to the tubes, BW weld the suspension brackets on first then the bearing seats are machined so even if the tube are bent the line through all bearing centers is spot on, my axle tubes did not line up once cut even though the bearing centers were aligned

The tubes will be plenty strong i cut the tubes so that the the lower arm mount will be on over of the joint, i have spoken to Ray McDonald and he says its fine

Theres no worries with engineering this method in NSW and as far as i know its fine in all states, well at least it was a few years back , the new 9" housing in my cortina was built by qpaac in qld and the billet tube ends are welded on in the same manner and i know of lots housings that are done this way


The hardest part of the job was removing the old brackets everything else is very simple, I've maybe put 2 hours into it so far and less than $250 including the price of the diff and the jig

[stealth]

well i got to agree with you on a couple of things
yes the are heaps of diff done that way ,but there weld in a jig like your then the housing heated and straighted that how gav at qpac does them
yes its cheap enough to do if you got all the gear
but no its not that cheap when you factor in getting the axel shortened (in you cant do it your self(im lucky there)
and the assembly of the centre afterwards ,again if you dont have the spreader tool and have to go to a diff shop
thats really costy
the one thats in my green machine is a ba falcon ute and does the job nicely (now its got a full spool in it as the factory style lsd's are a waste when you drive like i do







there's a couple of happy snaps of it in a la lancer
cheers stealth

[amgis_obrut]

yeah that is the better way to go and i did consider doing it that way but this way will be just fine for this car

BW dont heat and straighten their welded housing and just machine the tube ends to be aligned with the center

If i were to align my joins and then straighten the housing it would put the bearings out requiring me to machine the bearing seats true, it wouldnt be out by much but just enough to make the bearings wear quicker

If i could take a pic of the center line of the axle tube youd just about fall over with how un-centered the tubes are with the carrier

While this is the first housing i have done on my own at home its not the first diff that i have shortened this way, appart from a few hot rod diffs i partially done, i did the 9" in my first drag car that is still going strong 12 years on

The most expensive part so far was the spline @ $100 and the jig was $80, i already had a case spreader though i didnt use it as im using the same internal parts and have never used it to remove a BW center, only time i use it is if im fitting a center from another diff and need to work out shim thickness


Just a question

Why did you go with the old XF style brakes the EB onwards setup are soooo much better, I know they're vented but the calipers are not the best, i run the XF brakes on my Cortina and they're really not the greatest

Also are you sure thats a BA ute diff it looks like a pre EBII (pre BTR) sedan housing as it lacks the drain troff and the large drain bolt at the bottom of the housing afaik all the BTR castings have the drain troff and large bolt like the housing i have, i got a BA wagon diff out the back im pretty shure they're the same as ute also the dowl pins that are in the alloy cover are ONLY in sedan diffs that have the alloy wats link cover all utes and wagons have a pressed tin cover, Though i guess you can drill and fit the down pins

[stealth]

im using those brakes as its a gay requirment from the engineer (what he wants he gets)
its a very early ba ute diff out of a ford "test mule" as i have access to these items (involement in v8 supercar)
the rear cover is zl fairlane to use the watts linkage set up (cheap and easy) and the drain bolt i fitted myself and yeah fitting the dowels is easy with acess the the factory drawings
yes i do belive how far out the tubes are (pretty disgracful really)but that production spec
to quote ford specs "2mm end to end bend is within tolerance" i dont agree but hey
anyway good work and carry on good to see people having a go instead of moaning about prices!
i heated and alinened it after welding to save remachining of the tube ends
ps i hate the brake set up ,that said its works well i run ba front brakes also and you stand on the stop peddle and fuc- it stops
but you know why there so expensive for a diff shop to do ,but try expain that to someone how doesnt have the gear to do it!
cheers stealth

[amgis_obrut]

I got sick of paying for diffs to be built so i decided to start doing it my self same with pretty much everything, im like most blokes that build cars, I have no problems spending what ever it costs to get the good gear but if i can make it, i will as i find it very satisfying doing myself

though cars like my Cortina, where i want to have every thing spot on i like to pay the pro's

BTW your diff looks very neat

[stealth]

i got sick of paying for anything and everything and not getting value that why i started my own bussiness !
im shocked at the price for the recutting of the spline up here thay want $120 ,and thats my price (i do them myself anyway )
are you going to hollow the axel and have it hardened?
give its more strength and are you using the factory lsd ,these are the two parts that are a let down in a borg warner
mind you i have had numerous issues with mine ,broken multipul centres ,axels(till i hollowed) has to be 28 spline and i was considering going to 31 spline
then tryied a cusco lsd ,broke two and sold the third one before it snaped and now i got a romac full spool ,which is real interesting to drive
but im trying to engineer the sh=ta and need to go backwards ,but as i have toned down the engine this time i might get away with a decent limo
thanks (about neatness) i have been doing this sort of thing full time for 20 years now so i wouldnt expect anyless otherwise i may as well get out of the bussiness
and a good coat of paint goes a long way
cheers stealth

[amgis_obrut]

The old bloke that done the axle was part of the JPS BMW race crew years ago and still looks after the Gibson HR31 done alot with the 2.0l touring cars when they were running and builds heaps of historic race cars he's a clever old bugger

He says the heat treatment is nice and deep and theres no real need to do it again, he was saying that treating it again could in fact weaken the axle by making it brittle

He runs a home built BW diff in his 347ci windsor mk2 Jag track car its making 1.2hp per cube and he was saying he hasn't had any axle failures yet, had a few centers go but he now runs a TA Performance girdle and no more problems


I'll leave it until it becomes a problem and if it ever becomes a problem i'll just spend the $240 for a new billet axle

[stealth]

well i got to disagree there the "hardening " isnt that deep as there induction hardened ,AND only some models got hardened axels not all
the depth of the spline exceeds the depth of the hardness so it definatly needs rehardening ,that said if there done properly thay should anneal them first therefore thay wont be brittle
i will be looking into getting a girdle for the centre ,but old mate doesnt drive his car hard otherewise he would have had more dramas with axels ,thats my opinion
if you give it to them thay twist up quite easly,hence hollowed and hardened trust me i wouldnt waste my time or money otherewise
cheers stealth

[amgis_obrut]

Looking at the spline/gear hobbing machine that this bloke has in his shed kinda tells me he may have cut a spline or two in his life

Why waste money cutting, splining, gun drilling and hardening old wound up borgwarner axles, its cheaper to buy a new pair

Im doing this car on the cheap its not a priority ITS A SIGMA its not worth spending any real dollars on


The diff in my cortina would be worth more than most of the cars on this site I dont mind spending the $$$ on it because i dont want to have any dramas @ 135+ mph


I should really stop calling them a BW or borgwarner as ford haven't used a borg casting since early EB (or earlier) its all been the revised BTR casting like the diff I have, most wouldn't pick the difference but I have had heaps of these diffs and its easy to tell what is what


Also how did you get the X series yoke to fit the BA diff ? im guessing that BA test mule ute had an old borg cast XF diff in it

[amgis_obrut]

Suspension jig

Will add a pic with the diff in place tomorrow



this was easy to build i just put the housing bar through the sigma diff and then built the jig around it, once done i just cut the mounts off the diff and bolted them to the jig then sat the new diff in place

[amgis_obrut]

finished BTR housing, ready for assembly and installation, i had to make new offset upper trailing arms as the mount on the diff had to be moved outwards, i just used the falcon uppers with the sigma ends welded on, the top mounts on the diff are the falcon off cuts



Falcon upper trailing arms


fitting it was a breeze went in easier than the factory unit, still need to make a tail shaft and connect hand brake and brake lines



Plenty of room for wider tyres, well theres 25mm between the tyre and body, i could fit a 255 tyre if i wish

[amgis_obrut]

9 years on and this diff is still going strong
Its in another gh with an efi turbo 2.6

[JimmyG]

Well built right from the start.