73 240z.. On the rear diff I saw a 3/4 inch plug (pix below). I thought it was like other cars and that is where you fill the diff with fluid up to the bottom of the hole. When my son unscrewed the plug, fluid came pouring out. It took him some time to put the plug back in and lost about 1/2 quart that he is cleaning up now. The fluid is black so we plan on changing it but how do I drain all the fluid, where do I fill it from and how much fluid should I expect to need to fill it?

That one is the drain . There is another one above that one fill to it starts to drool out the top plug.

5 and 6

Edited November 29, 201113 yr by black gold man

ok that makes sense. BTW is the bar above the drain plug the "mustache bar"?

ok that makes sense. BTW is the bar above the drain plug the "mustache bar"?

Maybe.

Depends on which bar you are referring to.

The large, well-lit curved bar immediately above the drain plug? No. Not sure what it is called, rear transverse link bracket perhaps.

The hidden in shadow, wouldn't know it is a bar unless you are looking for it thing that the differential attaches to with two bolts? Yes, that is the "mustache bar."

Chris

The mustache bar is about 3 feet long.

The diff fill plug can be removed without removing that curved bar, it may be very tight.

An easy way to fill the diff, is remove the rubber plug in the spare tire well, thread a length of tubing (old garden hose) through it to the fill hole. The factory service manual has the exact amount of gear oil, not the fill till overflow method.

The tubing method can be used on the transmission also, remove the rubber plug under the ashtray, on the 73 anyway.

Transmission & diff drain plugs should be magnetic, gently wash off in solvent to see what they have caught.

Bonzi Lon

The mustache bar is about 3 feet long.

The diff fill plug can be removed without removing that curved bar, it may be very tight.

An easy way to fill the diff, is remove the rubber plug in the spare tire well, thread a length of tubing (old garden hose) through it to the fill hole. The factory service manual has the exact amount of gear oil, not the fill till overflow method.

Sure, now you tell me. Sounds like that method beats the hell out of scooping up the oil in my hands and shoving it in the hole.

Actually, never did that. Close, though.

The tubing method can be used on the transmission also, remove the rubber plug under the ashtray, on the 73 anyway.

Bonzi Lon

I just go through the engine compartment on my 1972.

Chris

...

An easy way to fill the diff, is remove the rubber plug in the spare tire well, thread a length of tubing (old garden hose) through it to the fill hole. The factory service manual has the exact amount of gear oil, not the fill till overflow method.

...

Bonzi Lon

The differential and transmission should always be filled until the oil level is even with the check plug bore. The oil capacity listed in the manual is approximate and is for reference only.

I'll follow what the Factory Service Manual 'recommends'.

Bonzi Lon

beermanpete: http://www.classiczcars.com/forums/showthread.php?44354-My-shifter-runneth-over-oil-in-s

Post 8

Bonzi Lon

Edited November 30, 201113 yr by Bonzi Lon

I'll follow what the Factory Service Manual 'recommends'.

Bonzi Lon

If you did, then you'd fill to the fill plug! Beermanpete is absolutely 100% correct on this. The FSM shows that the diff and tranny must be filled to the fill plug.

Bonzi Lon,

The 1973 Nissan factory service manual, in the differential section, specification section, page PD-12 states, "Oil capacity (about)...".

I always fill gear boxes (trans, diff, whatever) to the check plug. If there is a dip-stick I fill until it indicates full. I only use the capacity specification to determine how much oil to buy.

Running the engine, gear box, or differential with slightly less or more oil is not a big deal anyhow. It only matters when the oil level is so low that it overheats or cannot properly lubricate the bearings, or if the oil level is so high that the oil foams or expands until it flows out the breather. In between these two extremes it is not terribly important exactly how much oil is in there.

If you did, then you'd fill to the fill plug! Beermanpete is absolutely 100% correct on this. The FSM shows that the diff and tranny must be filled to the fill plug.

Yes, because it's the oil LEVEL not the amount of oil, within reason, that matters. Diff and trans housings are castings with tolerances that aren't very tight. The internal volume of a cast housing can vary because of that. So the volume of oil to reach the fill plug level can be different between one trans and the next. The fill plug location is pretty well controlled because it is machined into the casting so the oil level with respect to the gears is fairly precise if one fills to the fill plug. The gears are partially submerged in oil and splash the oil around and so the level of oil relative to the gears is what controls how much oil gets splashed around.

Steve