I took my m46 out a few years back with the help of a friend of mine. I do have overdrive so this made the whole thing intensely heavy under the car and I will never repeat the procedure without a hoist or a pit or something that allows me to get some serious hands on the damned thing.

With mine I found very little space to move back or forth before I ran into the metal of the hump and this made the whole operation very difficult and complex, especially while doing all of this under the car. Frankly, we had a helluva time with it. We had earlier done the transmission on my earlier car, a 142 without overdrive and it was a snap.

We ended up having to raise and turn the transmission before we could get it to go forward [installing, here] and then we got into the usual hassles trying to get it forward and onto the splines. Just a pig of a job. I wish I could offer you some advice but it sounds like you have done everything right and it is just hanging up on the splines for some reason.

Good luck.

Bob