Originally Posted by BlueOvalRage

I’ve built a few and I’m actually in the process of putting one together now. There are a few little tricks and experience helps too. Personal preference, skill level, and how much patience you have can also dictate the best way to do things.

Slop is your enemy on these transmissions. It makes them noisy, prone to breakage and shift like crap. Slop is also one of the major contributors to popping out of 2nd gear, which is a very common complaint. Unfortunately, they were sloppy right out of the box and 60s year worth of wear on top of that certainly doesn’t help. I will mock various assemblies up in the case numerous times until I get the fit of everything just right. Start with the countershaft assembly. Set it up in the case by itself and check the end play by inserting feeler gauges between the rear of the gear and the rear thrust washer. Ford’s spec is .0045” to .0185”. That’s a 14 thousandths range! Waaay too loose at .0185”. It should be held to .004”-.010” and the tighter the better. A new gear with new thrust washers may need to have the washers dressed a bit to get enough clearance. .004” is the absolute tightest you should go as the gear will grow as it heats up.

The other area that you really need to watch as far as clearance goes is at 2nd gear. Mock 2nd gear and the 2nd gear synchronizer ring and hub up on the output shaft without 1st gear, snap rings or the rest of the synchronizer assembly. Just 2nd gear, the synchro hub and 2nd gear ring. Stand it on its tail end on the bench and push down hard so the hub is pressed tightly against 2nd gear. There must be enough clearance so that you can rotate the synchro ring. It can be snug and drag when you turn it, but it MUST be able to be turned with your fingers. If the assembly is so tight that you cannot turn the synchro ring, then your synchro hub is most likely worn where 2nd gear rides against it. It will burn up your synchro ring quickly if you don’t have adequate clearance for it to work. There’s not much chance that it will be too loose. Too tight is the concern here.

Once that is dialed in, assemble the output shaft, bearing and rear housing together and put 2nd gear, the synchro hub and the 2nd gear synchro ring on it without a snap ring just as it was for the last check. Insert this partial assembly into the empty housing with the gasket in place. And snug up the bolts. Now assemble the input shaft, input shaft bearing, and bearing retainer to the case. You MUST have the gasket, input/output shaft needles and the 3rd gear synchro ring in place also. Your assembled parts will be input shaft and bearing retainer, input/output interface needles, both synchro rings and the hub, 2nd gear, output shaft, and rear housing along with front and rear gaskets and obviously the bearings. Grasp 2nd gear and shove it along with everything forward of it towards the front HARD and measure the clearance between the back of 2nd gear and the shoulder of the output shaft that it rides against. Ford’s spec for this is .003”-.011” which is reasonable. Chances are that you will find that your clearance is waaay more than that because of housing stretch and stack up of wear on parts. Excessive slop here is the primary cause of the tranny popping out of 2nd gear. If none of your parts seem excessively worn, then the fix is to have a machine shop mill the rear face of the case by an amount that will bring the assembly back into spec. For instance, if you measure .046” like I did on the unit I’m building, then you would need to have the machine shop mill 42 thousands off the back of the case. This allows the output shaft assembly and rear housing to move forward and take up the slop. It should leave you with about .004” of clearance which is nominal.

Some guys like to use lots of assembly grease to stick the needles and thrust washers of the countershaft assembly in place and that does work. I personally prefer to assemble them with everything squeaky clean and bone dry. The only thing I lubricate during assembly is the needles that run in the end of the input shaft. I use some Vaseline to hold them in place until the shafts are seated together. The reason I assemble everything dry and clean is because I seal the countershaft to the case with Loctite 641 retaining compound to eliminate leaks and keep the shaft from fretting. Any assembly lube anywhere will contaminate the surfaces and keep the Loctite from properly bonding. These trannys are notorious for leaking at the housing/shaft joint and this permanently fixes it. This method absolutely requires using a dummy shaft that is just small enough in diameter to slip out through the hole in the front of the case and the exact length of the cluster gear. I load all the needles, thrust washers and spacer onto the dummy shaft with little rubber bands that my wife uses for her hair. Roll the rubber bands back and cut them off as you insert the assembly into the cluster gear. If your dummy shaft is correctly sized, it’s not as hard to do as it sounds.

I begin final assembly with the case in a vise or fixtured so that it is oriented as it would be in the truck. Drop the cluster gear along with the FRONT thrust washer in first and slip the rear washer in behind the gear as it is dropping into the housing. This is the toughest part of the whole job and requires three hands. The tangs on the washers will keep them from falling completely out into the bottom of the case. The cluster gear needs to be sitting on the floor of the case. Install the entire output shaft and rear housing assembly in next and snug it in place. Next is the input shaft and needles followed by the bearing retainer and gasket. When you’re satisfied that everything in the input shaft/synchronizer/output shaft group is assembled correctly, carefully raise the cluster gear up to mesh with the upper gears and align the thrust washers to the case holes. Again, it helps to have extra hands here. Once the alignment is good enough to accept the shaft, start inserting it slowly from the rear and it will shove the dummy shaft out of the front. When it is inserted just to the point where it is ready to enter the hole in the front of the housing, stop and coat the remaining stub at the rear with Loctite 641 and also brush it liberally into the bore in the front of the housing. Double check that the retaining pin hole is properly oriented and drive it home. Verify that that pin fits correctly, remove it and walk away for the day to let the retaining compound cure. Insert the reverse idler, shaft and retaining pin with the same Loctite procedure the next day and let it sit again. The balance of the assembly process is self-evident.

It will feel stiff as hell and turn harshly after assembly with no lube, but once the Loctite cures, you can oil the innards up well before installing the shifter cover and it will smooth right out. It’s time consuming and somewhat expensive to build one the way I do, but the end result is a quiet, smooth-shifting transmission that stays in gear and will stick together for many, many years. NOS and NORS aftermarket gear and parts for these trannys are abundant on eBay. New synchronizer assemblies are available too. There’s no reason at all to cut corners. If it needs replaced, replace it.