How To: C15a Wire-3 restoration

[Jordan Baker]

The joys of old trucks. Doing maintenance. Last week I drained and fill the diffs to change out the gear oil. However I overfilled the rear diff and ended up noticing gear oil draining from the drip hole on the brake backing plate. There was also some staining and the odd time a small dribble from the axle end on the hub. Today I pulled it all apart to do some cleanup and get it so it isn’t leaking. Thankfully the inner cone did its job and kept and leaking oil from getting into the brake drum or on the shoes.

Tomorrow I hope to be getting everything back together again.

[Lynn Eades]

Jordan if you install outer hub seals, that will restrict the oil to the axle tube. This means you can pack your bearings with grease, which baring a major failure, means you should never have oil getting to your brakes.
I say this for those that don't know (because I know you do) Make sure you clean out inside the shield and the tell tale hole.

[Grant Bowker]

Jordan,
I don't know whether this may be part of the issue or not. M35 and M135 series trucks used a cork seal (wedge shaped) in the keyway/groove highlighted by the arrow in your 3rd picture above. The wedge/insert was claimed to be part of the sealing to keep lubricants where they belonged. The attached diagram lifted from the web is one of the clearest I've seen to date showing where the wedge sits. There are also web posts claiming that a blob of silicone can replace the wedge.

I don't see a reference to the wedge seal in the C15A parts list but I may not have been looking in the right area of the list or might not have recognized what the list called it.... so I'm not sure whether the CMPs used such a seal.
Having said that the seal may be used and might be significant, I don't recall if my C15A has them but I certainly dont recall making them as suggested by many from old valve cover gasket material , or from sheet cork gasket material.

[rob love]

My understanding is that the cork gets pinched in between the two tabs of the washer and the seal. That is the way I have been doing it for the past 40 years. The corks are not tapered on either end. I have dozens in their packages at work, so these are factory design originals as opposed to the cut valve covers.

Edited to add: Grant, I checked the MLVW manual and the illustration you have is wrong. The cork goes in between the seal's tab and the tab washers inner tab.

Not sure the Chev ever had the cork, but it would help if the truck for some reason leaned enough to let the oil get in to the top of the spindle, or was splashing it to the point of putting oil onto the top of the adjusting nuts.

In Jordans case, we were having email discussion on this, and he had filled his diff to the edge of the filler hole. Normally you go one knuckle lower to allow for expansion, and even a half inch lower won't hurt, but will help prevent leaks. And of course, the breather valve must be clean.

[Jordan Baker]

So I went through my box of parts and pulled out a some NOS outer seals. Thought I would compare the two. Take off is on the left and NOS on the right. There is about 1.5mm difference between the two. When I dry fit the two seals in the diff there is noticeable looseness with the takeoff one. I figure that between this seal and the overfilling of the diff that’s where my problem was coming from.

[Jordan Baker]

Everything is back on with freshly repacked bearings. The NOS outer seal was a much better fit (tight against the hub) and I now understand how these parts work.

Thanks all for the help. When I refill the diff up I’ll be sure to keep it lower then I did.

[rob love]

The outer seals are leather. They should be soaked in oil for a few hours before installation.