Differential fill plug?

[Bazzalucas]

Hi all, I am putting a 3.7 diff in my 1958 rear axle. Naturally, this swap means I lose the fill plug. My question is, if I were to drill a hole in the appropriate place in the "pumpkin", would a good epoxy (JB Weld is the stuff of choice over here), be sufficient to retain the fitting into which the plug would screw, or is welding the only way forward? Alternatively, could I use an expanding rubber plug (as used in plumbing applications) in said hole? (This assuming there is adequate clearance between the plug and the crown wheel) Thanks in advance for the input.

[chrisryder]

Find or make a small funnel, and remove the breather on the axle each time you want to fill it, then use that hole. don't fill it right up though, just pour the correct volume in.

[liammonty]

I drilled, and then welded (badly) an appropriately sized nut on to the diff casing of mine, and then used chemical metal to seal (and hide!) my terrible pigeon-poo welding. You can then use a matching short bolt with a copper washer as a 'plug'. I wouldn't rely on filling it from the breather- it's a bit of a bodge. If the diff leaks you'll never know how much oil is in it.

I wouldn't rely on epoxy alone to hold the nut in place- I think the torque when you do it up might be a bit much for it to hold.

[Stig]

I ran mine for years with a diff where the filler plug was seized and filled it via the breather hole. I used a bit of stiff wire as a dipstick.

[bmcecosse]

You would do MUCH better to drill and tap the new diff assembly for a plug. DO NOT rely on epoxy glue.

[liammonty]

Drilling and tapping would be ideal, but in practice, but unfortunately, there just isn't enough metal to do that on the older axles- they're not built up around the area where the filler is on the later ones. That's why I had to resort to welding a nut in place having drilled the case- it's the only way to do a half way decent job (well, if you can weld better than I can...).

[bmcecosse]

It doesn't need to be a huge hole - just enough to get an oil-can spout through.

[Bazzalucas]

BMC- do you mean the aluminum casting, rather than the steel "pumpkin"? I assumed that that had been discontinued because of some strength issue or other.

[dellerie]

when changing oil, drain out as usual through the plug at the bottom of the banjo casing.

when filling, after draining, jack up one side and remove the drum. (chances are, you'll need to inspect the linings at some point anyway) remove the halfshaft and fill up through the halfshaft hole. fit a new gasket and your off and running. no mess and the correct amount in.

simple.

[bmcecosse]

Yes - I did mean the ally casting. But the jack up method will work fine too - and it's not something that you have to do any too often.....

[Bazzalucas]

I think, since I have the diff sitting on a bench, that I'll try the drill-n-tap approach. Much easier to get all the swarf out.

[bmcecosse]

Exactly!

[Bazzalucas]

If someone has a pic handy of the fill plug location on the older diffs, could they kindly post it? I don't trust memory to serve in drilling the new one. Thanks in advance.

[Bazzalucas]

Never mind the photo. I found an old parts manual with the proper location. Drilled, plugged and ready to install!

[bmcecosse]

Good job well done,,,,