I wouldn’t try to expand the bell joint. A 3/4-36 spline should slide onto the steering box spline without having to spread or deform the bell.The measurements you’re getting with calipers can be misleading, especially when measuring across the spline teeth. I’d first make sure the splines are perfectly aligned and that there isn’t a burr, raised edge, paint, or plating on either the rebuilt box shaft or inside the bell.Since it came apart easily before the rebuild, I’d compare the rebuilt box shaft carefully with the original shaft and check the spline diameter/profile. Also try sliding the bell onto the shaft with the pinch bolt completely removed/loosenedthe clamp can remain slightly closed and make the joint seem too tight.A light coat of grease on the splines is fine, but don’t force it with a hammer. If the original bell slid easily onto the old box but won’t go onto the rebuilt box, I’d suspect the rebuilt shaft dimensions or spline profile before modifying the bell.If you can post a close-up photo of the shaft and the inside of the bell, someone may be able to spot what’s preventing it from seating.
