Slinkyfox 66 Posted May 13, 2015 My te cortina's got a 25 spline 2.9 open borg diff in it. The car's currently stock, but I've got a warm crossflow & manualised c4 2800rpm stall that I'm about to put into it. Ive also got a 5 stud front brake setup & wheels. I've been researching a lot into 28 spline 5 stud conversions for the corty diff my question is, how much can 25 spline axles take?? I'm guestimating the motor should have around 250ish fly hp, do you think if I get my axles & drums re drilled & put a shorter set of gears put in it will hold together? Its my daily so will only really get the odd run from the lights. And Maybe one run down the strip to see what it does, seeing as wsid is around the corner. I don't mind spending money on the 28s lsd etc if the car needs it, just curious what people have gotten away with with the 25s. Got another build on the go & wouldn't mind saving a bit of coin if I can. Share this post Link to post Share on other sites
slydog 7,873 Posted May 13, 2015 25's will take more punishment thru a auto but there is a limit for sure. TBH just upgrade to 28's and deal with it when the 25's break. 3 dougie77, Slinkyfox and Mixalis reacted to this Share this post Link to post Share on other sites
Mixalis 266 Posted May 13, 2015 Yeh Ive had 25 spline through my first 2.92 open centre, then 2.92 LSD and now 3.45 LSD (last two are the same diff) and they've held up fine, mine doesn't make too much power tho 166rwhp thru a BW35 so idk maybe 210-220hp engine? thats with about 15 or so passes thrru them all together plus street driving where i generally take care of it well. Like Rob said tho auto loads em up and gets rid of that 'snap action' so to speak. Mines half way thru a single rail conversion tho so should be interesting to see what difference it makes. 2 slydog and Slinkyfox reacted to this Share this post Link to post Share on other sites
wagoon 2,429 Posted May 14, 2015 I think it will come down to you and the way you drive. I went to school with a guy that had a standard auto vl commonwhore ( same 25 spline borgy) and he could not go a month without blowing a diff. I plan on using the stock 2.77 open diff behind my hopefully 350hp manual crossflow, I will just keep in mind that its there. I will be upgrading to 28 spline but just to get the car running it will do. 1 Mixalis reacted to this Share this post Link to post Share on other sites
gerg 10,871 Posted May 14, 2015 Also comes down to diff ratio, higher the number the greater the torque multiplication to the axles. I reckon a 2.78 or 2.92 would be fine behind a manual if not abused. Shock loading is a different story... Sort of like resting a hammer on a glass table versus dropping it on there 1 Mixalis reacted to this Share this post Link to post Share on other sites
thunderbolt 150 Posted May 14, 2015 It depends on traction too and your more likely to break an axle or side gear with fat sticky tyres. 1 Mixalis reacted to this Share this post Link to post Share on other sites
Xelisty 366 Posted May 14, 2015 The tailshaft went on mine first so if a manual get the ef tailshaft installed and stronger unis. I have a good tight LSD with 2.92 ratio in a t5 with a turbo 310rwhp crossflow with 255 mt steets. Maybe 40 to 50 runs down the drag strip. More coming Saturday. Good noise when it goes bang My guess the axles are next so when they go they go. Sent from my iPhone using Tapatalk 3 Mixalis, wagoon and gerg reacted to this Share this post Link to post Share on other sites
gerg 10,871 Posted May 14, 2015 Oh yesss yummy carnage Share this post Link to post Share on other sites
PRO250 1,506 Posted May 14, 2015 As a auto it will be ok for a while, if running street tyres if its a spooled diff it will die fast if you give it a hard timeI ran a 3.9 limmo in one of mine with a engine making 230rwhp and it held up ok I busted the coupling once and twisted the axle ends twice but it would unload the tyres easy under 70kmhOn slicks they do not last andys TE makes 170hp and is auto on slicks its killed a few diffs now manual ive smashed at least 5 diffs and more then 30 axles they hold up ok on street tyres as soon as they hook up they bust everything 2 wagoon and Mixalis reacted to this Share this post Link to post Share on other sites
Mixalis 266 Posted May 14, 2015 That should be pretty much all the main factors then in determining the life span of those axles. Xelisty you still running 25 spline axles under that combo? Share this post Link to post Share on other sites
Xelisty 366 Posted May 14, 2015 That should be pretty much all the main factors then in determining the life span of those axles. Xelisty you still running 25 spline axles under that combo? Yea all stock was fully rebuilt throughout costing a bit too. Forethought I would of gone a upgrade instead rebuilt but live and learn. Sent from my iPhone using Tapatalk 1 Mixalis reacted to this Share this post Link to post Share on other sites
slydog 7,873 Posted May 14, 2015 The tailshaft went on mine first so if a manual get the ef tailshaft installed and stronger unis. I have a good tight LSD with 2.92 ratio in a t5 with a turbo 310rwhp crossflow with 255 mt steets. Maybe 40 to 50 runs down the drag strip. More coming Saturday. Good noise when it goes bang My guess the axles are next so when they go they go. Sent from my iPhone using Tapatalk Have you thought about a flat flange E series style unit bro ? Share this post Link to post Share on other sites
Xelisty 366 Posted May 15, 2015 Got that change done when the tailshaft broke. Ef tailshaft and hardy spicer sealed unis Balance is better too 1 slydog reacted to this Share this post Link to post Share on other sites
