I know they're different, I know AP2 has M10 bolts, you can use a M10 (M8-1.25) x 60mm Socket Shoulder Bolt, Alloy Steel (Box of 50) to bolt it to the flange. My question is, will the cap on the AP2 prop shaft let you bolt it up to the AP1 diff flange? Because if the cap isn't interfering and it's just the bolt size difference, then you can just use those shoulder bolts to slap on an AP2 prop shaft on your AP1.

 

No, the centering ring dimensions are different, see here:

However if you could swap on the AP1 end caps to an AP2 shaft(maybe enlarge the holes to 10mm if needed), I think you could bolt them on with the shoulder bolts to the AP1 trans/diff flange.
Can someone confirm if the end caps are interchangeable between AP1 and AP2 shafts?
If it would work I would buy an AP2 shaft and rebuild it with new CVs and make it work in my AP1 with AP1 end caps and shoulder bolts, as there is no proper replacement CV for the AP1 23 spline design.
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Puddymod seems to use ap2 flange for an AP1 shaft rebuild.

 

Yes, I have seen that. Maybe the outside diameter of the centering rings is the same on both shafts end caps, or maybe he does some machining on them, I am not sure.
It would be awesome if someone could test this.

 

You can use an ap2 shaft on an ap1 (or vice versa) but you need to swap the output flange on the transmission and the input flange on the diff to pair with that driveshaft.

 

We know that, that was not the topic of this thread. In fact, the topic of this thread is, if you can use the AP2 prop in an AP1 without swapping flanges.

 

It is confirmed, the diameter of the centering rings is the same on AP1 and AP2, so it is possible to install an AP2 prop in an AP1 with AP1 flanges and the proper shoulder bolts(10mm to M8 thread).
After contacting NAUS, he was kind enough to measure his spare AP2 shaft and I was able to compare the dimension to my AP1, see in the pics bellow.

 

Ty sir this is going to help a lot of AP1 owners.

 

For your information, the correct shoulder bolt to make the AP2 prop fit the AP1 flanges with correct thread engagement is ISO 7379 M8 10x45 (d1=10, L=45, b=13). These are grade 12.9, so it is an upgrade from the soft, easy to round OEM bolts as well.
Additionally you need to order 6x AP2 prop shaft washers to fit the 10mm shank of the shoulder bolts, part number for that is 40140-S2A-A01.
Thank you to NAUS once again for the measurements of the AP2 joint widths(it is the same on both ends).