LINK TO ORIGINAL POST:
https://www.fordbarn.com/forum/showthread.php?t=278347
Here is where many things are going to happen. The cluster gear and reverse idler gear are already placed in the gearbox, and the main drive gear has been put in the front of the case. The mainshaft has been installed in the overdrive adapter, along with the remaining transmission gears (low/reverse slider gear, second gear, and the synchronizer assembly).
I place the gearbox front face down on my work bench, positioned so that the main drive gear sticks downward through the hole I have in the bench for that purpose. I have just trimmed and placed the rear face gasket to the backside of the gearbox casting. I have also placed the caged roller bearing inside the pocket of the main drive gear, and the high gear synchronizer ring on the tapered cone of the drive gear.
I carefully hold the mainshaft & gear assembly so that the front end hangs down through the back opening of the gearbox, guiding it down slowly so that I can position the front pilot end into the caged roller bearing in the main drive gear. During the final movement downward, I must align the front synchro ring slots with the matching synchro inserts on the front of the main synchro assembly. It helps to slightly rotate the drive gear from below while making the final drop......you can feel the two components line up and drop into place.
Since we had already just positioned the rear gasket with fresh sealer, I want the overdrive adapter (with the gear stack) all the way down against the back side of the gearbox. Sometimes it helps to tap it down with a soft hammer. Make sure that the 4 bolt holes are aligned. Then, install two of the four bolts with washers to tighten the castings against each other. This will remain this way at least overnight. However, we can proceed with more assembly in the meantime.
Once I return to the assembly, the cluster gear and countershaft have to be positioned in place.....remember that the cluster gear has been sitting on the bottom of the case (with bearings, spacer tube, and thrust washers). The cluster gear must be raised up so that the 7111 countershaft can be installed through the gear and case. The first photo of this process shows the misalignment of the cluster gear when looking through the countershaft bore in the back of the case. The second photo shows how the gear, roller bearings, and rear thrust washer have been aligned with a tapered drift. It helps to slightly rotate the mainshaft gears to let the cluster gear ride into mesh with the mainshaft.
The next photo shows the 7111 countershaft inserted into the case (through the OD adapter, the gearbox case, the rear thrust washer, the spacer tube, and the two roller bearings). I mark the end of the 7111 shaft to draw a line showing the direction of the lockpin hole. As the shaft is worked all the way into the gearbox, this will need to be correctly aligned with the lockpin passage in the case. Otherwise, the lockpin can not be inserted all the way through both shafts.
A look at the next picture shows how I get an eyeball on the alignment of the shaft by placing the lockpin temporarily in the passenger side opening for the lockpin. Do not push the countershaft all the way in yet as the front thrust washer must now be wiggled into alignment. By setting the gearbox in its regular horizontal position, you can use a tapered drift punch to align the 7119 front washer, and then work the 7111 shaft through it.
Once the countershaft is started through the front thrust washer and into the front bore of the gearbox, you can stand the transmission back up vertically and finish tapping the 7111 shaft down into place. I use a small flashlight to shine a bright light through the lockpin passage. That way I can see that I have tapped the shaft far enough into place AND that the shaft is still rotated correctly to let the lockpin pass through the countershaft. If it's not aligned, tap the 7111 shaft out and rotate it slightly to get the correct pin hole location.
Lastly, push the 7155 lockpin into the case (passing it through both the 7140 idler shaft and the 7111 countershaft). The small head of the pin should sit flush with the side cover mounting surface. I usually smear some sealer on the pin before I tap it into place.