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October 16, 2026, 07:25:22 PM

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[winton]

thought I'd start a thread about how I achieved fitting 28 spline axles into my corty housing .

pretty simple.
Probably best to pick up a complete skyline diff including brakes, this means you will have a set of 3.9 gears too, or get the pintara r31 diff for the 4.11 but you will need to get skyline axles. Also get either a spool or LSD + bearing .

Removed the wheel bearings from the skyline axles.where the bearing seats you need to get 10mm turned off  the axles so they will sink deeper into the housing .


also the area the seal runs on needs to be turned down/extended or the seal will bottom out.


 I don't have a
lathe so I payed a guy to do it cost me $120.  I forgot to take a picture of the modified seat and seal area, this is the best I can do. A little annoyed at myself but if anyone's going to attempt this you should be competent enough to work it out.



After the seat a was shortened  it made the short axle the correct length but the long 10mm to long, so I cut 10mm of the spline end. When fitted it wouldn't go all the way in as there was not enough spline left. fixed this problem with a angle
grinder fitted with a cutting wheel, nipped the end of the splines by about 3mm witch was enough to sink it flush . I had a lsd center fitted, not sure if this will be a issue with a spool. I'm going to pull it back down so I will take some measurement and ad to post.



before fitting new wheel bearings you will need to get the retaining plates off the original corty axles.

Now that I was happy with the axles in the housing, I cut the section out of the drum backing plate to fit between
the retaining plate and housing keeping the original bearing pre-load.

brakes.
I'm stick with the r31 skyline pattern ATM. (114.3x 4) so I
fitted the disk straight on the axle flange. I welded the caliper mounts to the housing, but you could fit longer bolts through the axle retaining plate and bolt behind  the caliper mount.

Obviously you could have the axles redrilled to whatever pattern. I got quoted $140 to redrill and $30 to drill the disks.

I haven't run this in my car yet and haven't figured
out what I'm going to do to hook up the hand brake. But am thinking along the lines of little u clamps then solder the join.
May end up having one made but will see if I can fabricate something before I go that far.

once this set up is done the diff is shorter by 30mm each side but you lose 5mm once disks are fitted.


note r31 pintara axles are 25 spline, r31 skyline are
28 spline.

I'm also considering doing another one to fit drums. Basically as above but cutting/shortening  the housing and sleeving the bearing seat to achieve the same offset as a corty axle, so it looks as if it hasn't be modified .

As you can see I have little space but moving soon then I can get stuck back into my cortys.

[unch55]

hey winton. interesting topic... thanks..
im looking at doing something similar to my TD rear end. ive only got a 250 crossflow but its putting out 300HP ( fitting it in a few weeks) so im worried the standard diff wont like it.. although many years ago i did have a 351 clev in a TC and did many burnouts without any diff dramas,,,
look forward to any more info you might have with this mod..
it would be ideal to not have to modify the brakes etc.... and just swap the center and axles ...

[winton]

hi unch55.
i have a spool fitted and with the standard 25 spline axles and i only get about 200ks out of them.

I tried to use the standard drum brakes by mounting them further down the axle tube (to compensate for the shorten track) but it was a pig of a job. the hand brake arm fouled on the housing and i was worried that it would end up pulsating through the pedal if i didnt center it properly, It could be possible to use the standard drum brake by fitting a spacer between the flange and the drum using the original backing plate and mounts, when i do some more work on it i will check if there is enough room that the flange wont rub on anything. properly wont get to it for about 3 months .

[winton]

Awhile ago I was asked about how I fitted the caliper mounts, so here's some pictures

[becks]

How much hp do you think you can safely run with this diff??

[winton]

I've read that the 28 spline axles with a spool are good for up to 400 hp.  With a LSD they could take more, but I can't confirm till I fit and test.

[becks]

Good post/info and photos buy the way