What happens in a transmission rebuild - Part 5
 

LINK TO ORIGINAL POST:
https://www.fordbarn.com/forum/showthread.php?t=278347

These sections will show our prep work on all of the gearbox castings. In this thread I will focus on the overdrive extension housing (or the "tailhousing" as most people know it). The first job is to install the rear bushing. This is a steel shell which is lined with a softer bearing material, and has the oiling grooves. The slip yoke of the driveshaft will fit in here, and it's important that there is a close fit between the bushing and the slip yoke. The close fit will help reduce gear oil leakage, and it will keep the slip yoke aligned properly with the transmission mainshaft.

The bore in the extension housing should be smooth and lightly oiled for the new bushing to press in smoothly. There is a channel for gear oil to help lubricate the slip yoke, and the oil slot in the bushing should align with this channel.

I set up the housing in our 20 ton press. Use a soft material (in this case it is an aluminum block) to push on the edge of the bushing. Make sure the bushing is as straight as possible before exerting pressure on it. Once started in, I continue to press it down until my block hits the lip of the housing. Then I switch from the aluminum block to an old socket (which is slightly larger in diameter than the bushing) and finish out pressing the bushing into place.

BEFORE we press the oil seal into place, we always check the fit of a slip yoke in the new bushing. Sometimes, there will be a slight deformation of the outer lip of the bushing and I use a curved metal file to dress the edge of the bushing. I drag my file from inside to outside to keep the fine particles outside of the transmission housing. I retest the fit, making sure the slip yoke slides in okay and rotates by hand. On some occasions I have had to use a small brake cylinder hone to remove a bit more material if the yoke remains too tight for a proper fit. In this case, you will need to carefully blow out the housing from inside out and wipe it down.

Once I am satisfied with the bushing fit, I proceed to install the rear oil seal. The type you see in this picture has a steel shell and two types of seal....the inner neoprene-like lip seal.....and the outer felt ring. Be sure to install it with the felt out! We use many special "tools" in our press. In this case, I have an old bearing race that is the same OD as the shell of the new seal. Using this prevents the shell from denting or buckling as we apply pressure. If you deform the seal, it is likely to leak. I also smear a film of Permatex gasket maker RTV sealer in the cavity of the housing before pressing the seal in. This help prevent any oil leaking from around the outer diameter of the seal due to irregularities between the seal and the cavity. This type seal is wide enough that part of it remains outside of the extension housing, even after fully seated internally. This is normal.

Re: What happens in a transmission rebuild - Part 5
 

Now we will follow up on the rest of the overdrive extension housing prep work. The overdrive mainshaft ball bearing is located by a unique snap ring (7656 in the drawings), and this ring fits into a groove machined into the interior of the housing. The ring must be reduced slightly in diameter to fit into this groove. A pair of long-nosed pliers is used to grab the upturned ends of the ring, and place it into the intended location. A cut-out area in the lower part of the housing allows for this to occur. Once fitted into place, you rotate the ring until the upturned ends are located at the top of the groove.....they will be visible from outside the housing by looking into the rectangular opening above the groove.

Having placed the snap ring, we then install the overdrive lockout shaft seal into the side of the housing. I run a brass wire brush in and out of the opening to make sure this passage is clean. Then I smear a bit of the Permatex gasket maker around the open recess for the seal. Just press the seal into the recess, making sure it has seated fully. We want this to set about 24 hours to secure the seal tightly into place.