SteveHobart 57 Posted August 4, 2021 Hey all. I'm looking to change diff ratio on my XF Sedan. I've currently got a 25 spline BW running stock ratios (2.77 from memory). Want to go to 3.3's (ish). I heard that E series 28 Spline Diffs will fit and have available ratios (and can add a LSD). My question, what model E series will be a straight (ish) swap? Cheers Sent from my iPhone using Tapatalk Share this post Link to post Share on other sites
deankxf 20,288 Posted August 4, 2021 i you can find them.. 3.23 or 3.27 is fairly common., needs to be from a coil spring diff, (EA EB ED falcon, or NA NC or LTD equiv) LSD was an option, called "spin resistant differential" the EF and EL can also fit ... bit more mucking around. the EA had 25 spline axles, (fine for a mild V8 still) rest of them are 28 spline with solid discs (unlike prior had vented discs XC XD XE XF) EB /ED was the best choice if possible.. the series 2 EB diff and later you'll need to press in the wider lower bushes on the trailing arms, or add some washers to take up the slack at worst case.. hand brake cable from EA EB ED sedan will fit XE XF sedan with that diff the EA diff has the same yoke on the diff as XF, the EB onwards you'd ideally use the EB ED sedan tailshaft (you can swap the diff yokes, or you can probably get a hybrid uni joint but it's not likely as easy to find. with the brake line, you can get a metric to impreial adapter to use the diff brake hose (off the diff T piece) or you can do what i used to do(convert the brake line nuts to imperial on the diff at the T piece end.. and use the XF T piece... ) the EF EL diffs bolt up same, but you'll need to make up brake lines as they mount to the car at wheel arch ends not in the middle with a t piece.. hand brake cable also is a bit oddball . see what you can find, there's probably a tutorial on here somewhere for each.. this was off the top of My head 2 SirkWhyXF and Kiwi-E reacted to this Share this post Link to post Share on other sites
cisco 111 Posted August 5, 2021 13 hours ago, SteveHobart said: Hey all. I'm looking to change diff ratio on my XF Sedan. I've currently got a 25 spline BW running stock ratios (2.77 from memory). Want to go to 3.3's (ish). I heard that E series 28 Spline Diffs will fit and have available ratios (and can add a LSD). My question, what model E series will be a straight (ish) swap? Cheers Sent from my iPhone using Tapatalk As dean says "if you can find them". The last wrecker in Brisbane that I asked about xd e f parts said they had not seen any of them in their yard for 10 years. Remember too that you will need to change the speedo sender cog as well. Rocking horse poop or hen's teeth???? I believe the only straight swap will be from an EA. From EB on I think you will have issues with trailing arm bush widths and changing from yoke to flange connection to the diff. I could be wrong so check it. I had an XE Spac manual with a 3.25 drum brake rear that I changed to a 2.77 LSD disc rear from an XF auto Fairmont. It was a really good combo. Needed a tad more clutch slip taking off in first but from there on perfect. At 100 kmh on the highway it was at the start of the power band about 2300 rpm and you didn't even think about 3rd gear for overtaking. Just pull out and power on and the economy was great. Have recently repowered my 84 XE Fairmont with a blueprinted and balanced 250 Xflow and put a single rail 4 speed behind it. The rear is 2.66 with drums and I am sticking with it. Take off is fine, accelleration through the gears more than adequate and top gear has plenty of grunt. Economy is 13.4 l/100k with a Weber carb. With an XF fitting a V8 is not a legal option. If you are chasing better accelleration you do have the diff ratio option or upping engine horsepower. Turbo or you may be able to put a Barra in. My poliucy with Xd e & fs is to stick within the options they had when new. Best of luck and have fun. Cheers. Share this post Link to post Share on other sites
deankxf 20,288 Posted August 5, 2021 6 hours ago, cisco said: you will need to change the speedo sender cog as well. Rocking horse poop or hen's teeth???? the gears should be easy to find still. (new) 20 hours ago, SteveHobart said: Hey all. I'm looking to change diff ratio on my XF Sedan. I've currently got a 25 spline BW running stock ratios (2.77 from memory). Want to go to 3.3's (ish). why do you want to go to 3.23 ish? i'd also agree with Cisco and say i'd stay with the 2.92 or 2.77 (almost no difference in My opinion at 5%) if you have a cam that revs to 5500 ish, it will be doughy down low and 3.23 etc will help on take off a bit.. if the cam is stock, 3.23 is crap for a stock engine in my experience Share this post Link to post Share on other sites
Mr Polson 10,214 Posted August 6, 2021 if the cam is stock, 3.23 is crap for a stock engine in my experience Think it'll depend a lot on the gearbox too. My ute is great with a late E series T5 and 3.23 Share this post Link to post Share on other sites
SteveHobart 57 Posted August 6, 2021 why do you want to go to 3.23 ish? i'd also agree with Cisco and say i'd stay with the 2.92 or 2.77 (almost no difference in My opinion at 5%) if you have a cam that revs to 5500 ish, it will be doughy down low and 3.23 etc will help on take off a bit.. if the cam is stock, 3.23 is crap for a stock engine in my experience Thanks mate. It's not a road car, it's for blasting around a track/doing hill climb events.Engine has been modded, 10:1 compression, big cam, aftermarket ECU, soon to be running Turbo and E85. The 2.7's create too much of a gap between the gears, for instance, on the back straight at the track you can rev out 3rd, put it in 4th and it only just comes on song when it's time to jump on the brakes. Sent from my iPhone using Tapatalk 1 deankxf reacted to this Share this post Link to post Share on other sites
gerg 10,871 Posted August 7, 2021 Sadly I think you will run into carrier compatibility issues. The 2.77 ratio centre has a housing machined to suit that pinion depth, and is in the 75 (7.5" crown) series of BW diffs. The later gear sets (with deeper ratios) are 78 series and without machining, I don't think can be fitted to the 75 housing. The issue is that the step that the inner pinion bearing sits on is machined closer to the carrier, bringing the pinion further in to meet the smaller diameter crown. If you tried putting 78 gears in that housing, the pinion may be well too deep to get the crown in. You can go the other way (75 gears in a 78 housing) with a specific pinion bearing cup with a built-in spacing to suit, or there are shims to go under the bearing to space it in to meet the crownwheel.There are lots of traps to fall into with these diffs if you haven't researched which parts fit what series, and even then you can come across hybrids that have a mish-mash of parts that don't seem to make sense. I had one kindly donated to me that was an old 75 series 2.92 with disc brakes, big bearing axles, LSD centre but was only 2-pinion and 25 spline. It had a thick spacer under the pinion to get it to mesh properly, so the housing could possibly have been a 78 with 75 internals.I've seen a housing with "LSD" cast into the outside but was a 2-pin open centre.Best bet is to transfer an entire working diff over to your chassis. I did this using an XG disc brake diff but changed to an LSD centre and (eventually) 3.08 gears from a Commodore. It's only 25 spline but I don't drop skids or pop the clutch so should live a long life.I would have bought those 2.77s off you if I hadn't already built mine up. My 1st gear is a bit on the short side for my liking (EA T5 box).Sent from my CPH1920 using Tapatalk Share this post Link to post Share on other sites
deankxf 20,288 Posted August 7, 2021 4 hours ago, SteveHobart said: Thanks mate. It's not a road car, it's for blasting around a track/doing hill climb events. Engine has been modded, 10:1 compression, big cam, aftermarket ECU, soon to be running Turbo and E85. cool, see what diff you can find.. .might be lucky enough to come across a 3.23 EA to ED diff is the easiest Share this post Link to post Share on other sites
Thom 6,651 Posted August 7, 2021 Not always true but a general guide for e series diff ratios (you could order any ratio in any car when they were new but very few had different gears) this is generally from eb to el, early ea's still ran xf style diffs and ratios until the 4 speed autos were available 3.08: standard e series ratio gli sedans and futura mostly had this ratio 3.23: common ratio for fairmont, wagon, xg and xh utes base model fairlane V8 falcons (including xr8 up until el) 3.45: (almost all 3.45 diffs were lsd) xr6, el xr8, 6 cyl fairlane ghia, 6 cylinder fairmont ghia, manual 1 tonne xg and xh utes, outback utes (outback's had the hydratrack diff) 3 deankxf, gerg and bear351c reacted to this Share this post Link to post Share on other sites