Main Caps for 3rd member

Im starting my build on my 741 case for my spare set of gears. The case that didnt come with any main caps but my brother had a set of caps laying around so I grabbed them. One side matches up perfectly, but the threads on the other side do not thread in the same distance as the housing.

I spun in the adjusters to see if they would work and I got them about half way in on both sides before it got to tight for me to do by hand. I did this with just the bare housing, I didnt go further with the spanner wrench. Oh and the pic the threads do line up, I just have the cap loose right now.

Do any of you think this is going to be a problem?

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