77 Rear Diff Drain Plug

[Jimboss77]

So I read a tech post a few days ago discussing a rear diff rebuild. There was a lot of discussion about adding or not adding a drain plug. I happened to be under my Bronco today and noticed I have a drain plug on my rear housing. Question…..would this mean the PO added this or did some years have this feature? Didn’t think this needed added to the tech talk, I’m just curious so trying out the chat forum for the first time?

 

[okie4570]

Yes someone added it. 66 had one on the back of the housing, not all the way at the bottom either.

 

[Apogee]

None of the Ford 9" applications ever had a drain in the bottom part of the housing like that, and FWIW, that's a terrible design that would get scraped off the first time you drug it over a rock. Toyota has similar fabricated housings to the 9", and they weld a piece of tube around the drain to protect it, but guys still manage to unscrew the flush drain plugs from those on the rocks. I run an 1/8 NPT flush plug in the rear of the housing like a lot of others do here, but if I had your housing, I would weld a piece of tubing around that to better protect it.

 

[armynavy17]

Worth throwing out here that the risk of scraping off your specific drain plug varies entirely on how YOU use your bronco. While I agree there's nothing wrong with adding a little protection for it, it's not necessary if you don't wheel your bronco. It isn't something that's going to get tore off by a rock thrown from a tire of a semi.

 

[Jimboss77]

I figured it was an add on but had to ask. I’ve had several Ford trucks and another Bronco years ago too but didn’t remember any having a plug. If I were in an area where rocks or other obstacles like that were a concern I’d probably remove or cover it. We have mud, sand, and logs around here, deep mud I don’t intend to abuse this machine like I did others back in the day. My mud racing and borrowing backhoes and tractors to get out of ass deep bottomless mud pits are over. But man we had some fun

 

[thegreatjustino]

Yes someone added it. 66 had one on the back of the housing, not all the way at the bottom either.

That would be a fill plug on the '66. The '66 third member didn't have a fill plug like later years, so the fill plug was on the housing. Try mixing and matching years and you can end up with a '66 third member in a later housing and have no fill plug at all. Ask me how I know

 

[spap]

if It’s a concern you can try to find plug with an Allen head fitting that could be flush with the bottom of the housing
all depends how you drive your bronco

 

[okie4570]

That would be a fill plug on the '66. The '66 third member didn't have a fill plug like later years, so the fill plug was on the housing. Try mixing and matching years and you can end up with a '66 third member in a later housing and have no fill plug at all. Ask me how I know

A drain hose fits in there nicely though lol.

 

[Jimboss77]

Lol. So glad I joined this site couple years ago to learn all these things you can’t get from a manual. The biggest thing I’ve realized is you can’t be sure what you have with an old bronco. Mine appears to be mostly original except for the 70’s engine from a mustang. That and a few other personal mods from the PO. Glad to be part of a community with so much knowledge and willing to share.

 

[.94 OR]

When I did the rear end on mine, I purchased a pair of guarded drain plugs. One mounted under the passenger side axle tube and other on top to act as a fill point. Pull the stock fill plug to use as a fill gauge and start pouring in until it leaks out. Cap all holes and wipe up any residue. (pic was taken before I had filled with oil so the plug is just started in the threads)