Differential tool

[Topcot]

Just bought a 1940 Mercury and am wondering if there is a special tool available that is used to check the differential fluid. The plugs (check and drain)are square and smaller than 1/2 " & larger than 3/8" and look to be tapered. IF there is such a tool, where can I get one or does anyone have one for sale. Thanks.

[expavr]

Check with Vern Tardel. Several years ago I bought an all purpose tool he was selling that had lugs that fit all of the oil fill plugs on early Ford products including the large oil drain plug on the engine.

[Tim Brown]

I just use the end of a 3/8 ratchet wrench in that square plug hole. Its worked for years that way...

[rotorwrench]

Snap On actually makes male square drive ends to fit a ratchet or an extension so you can get some distance in tight applications. Ford had a square drive as part of the adjustable wrench in their OEM tool kits.

[V8COOPMAN]

If the above ideas don't work for ya, take a 1/2" drive extension and grind it to a snug fit on your grinder.........cheap and quick! Lasts a lifetime. DD

[scooder]

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I also just grab a 3/8" drive ratchet and have at it. Always removes the plugs without any drama.
Martin.

[Topcot]

Thanks to all about the differential "tool". Thinking I'll grind down a 1/2" to fit nicely. Good comments and advice. Now if one of you had a quick solution as to why my tail lights don't work and all other lights work....I know, ground. But finding it is tough since brake, directional, head and license plate lights work. Never a dull moment.

[rotorwrench]

If the wire is hot at the tail light socket, you may have a bad ground path. If the wire is hot at the light switch but not at the tail light socket, then it is an open circuit in the tail light wire, etc. You just have to start at the easiest stuff first and eliminate the possibilities. A test light or Ohms meter can be used to test the circuit. Brake lights are on separate circuit. 1940 models didn't have directional signals so you have some added circuits to check there and that might be where the problem is. The licence light generally works off the tail light circuit but it has a somewhat different ground path.

[deuce_roadster]

Take the bulbs out and check each filament with a continuity tester. If the ground was bad the brake lights wouldn't work. Could be both bulbs have burned out filaments.

[Brendan]

Originally Posted by scooder

I also just grab a 3/8" drive ratchet and have at it. Always removes the plugs without any drama.
Martin.

same hear

[ford38v8]

Originally Posted by Brendan

same hear

I here ya.

[SofaKing]

square and smaller than 1/2 " & larger than 3/8" and look to be tapered.

It is likely a 5/16 square drive, the taper is from years of being hogged-out with the wrong size tool. I bought a socket to remove the anti-chatter rod bolts. The plugs in my rear axel were so wallowed I welded bolts into the holes and wrenched them out while they were still hot.

[WestCoast]

when you get the plug out replace it with one that has the square head on the plug, any hardware will have them

[Ramblin Reck]

Originally Posted by V8COOPMAN

If the above ideas don't work for ya, take a 1/2" drive extension and grind it to a snug fit on your grinder.........cheap and quick! Lasts a lifetime. DD

V8COOPMAN
Excellent idea. Do you know the approximate dimension to grind it down to? I have about only one "get down and up" left in this old skeleton in order to check the fit if you know what I mean. Like would it be 7/16x7/16 which is half way between 3/8 and 1/2? Looking at my plug in the differential on my '39 it looks like maybe a 3/8 socket was used and got it a little buggered up.
RamblinReck

[Tim Ayers]

Originally Posted by ford38v8

i here ya.

lol!

[Kube]

Originally Posted by Topcot

Just bought a 1940 Mercury and am wondering if there is a special tool available that is used to check the differential fluid. The plugs (check and drain)are square and smaller than 1/2 " & larger than 3/8" and look to be tapered. IF there is such a tool, where can I get one or does anyone have one for sale. Thanks.

A 3/8" square drive should work just fine. If it doesn't, there are two things to check. 1) Often enough, the hole in the plug gets filled with "crud" and you can't get the drive in deep enough. So, be certain the hole is clean.
2) The hole in the plug is wallowed out by previous bozos that didn't remove it properly. If that's the case, I'd suggest you obtain replacement(s) is very good condition to make the next R&R easy on yourself.

[Bored&Stroked]

All I've ever used is a 3/8" ratchet. Hell, there is usually plenty of oil in the threads and they have always come out quite easily.

[1952henry]

https://www.ebay.com/itm/19539296189...Bk9SR76oz4H3YA


Or just get one of these. I have one, also a Blackhawk adjustable that works on innie and outie plugs.

[deuce lover]

Here is the tool and Ford script:
https://www.ebay.com/itm/39418896939...Bk9SR7D05IH3YA

[1952henry]

Adjustable wrench...

https://www.ebay.com/itm/25572063159...Bk9SR9LQioL3YA