Here's a copy paste from Page 20
The information posted below is rather long, but I suggest you all to read it, its worth the time and shall save you in a re-build.
Q. Will draining the transmission also drain the transfer?
A. NO ........ (one should not drain them unless one is certain that two have been contaminated with water or you are not certain whats inside and how much)
There are two drain plugs (M and N) but only ONE fill plug (L). You have to drain each one separately. Plug L is the fill plug for BOTH the transmission and transfer. When you fill up to the level (the threads of L) then you have filled both boxes at the same time.
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There are TWO drain plugs but only ONE fill plug. Everyone thinks there must be another fill plug, so they look higher up the gearbox and see a plug which looks just like a filler plug. IT ISN'T ! It is the reverse-idler-arm retainer and if you undo it, the arm will drop down inside the gearbox. The correct (and only) fill plug is low down (much lower than you would guess) on the side of the box.
Because of errors caused by the similarity of the fill plug and the idler retaining bolt, the Mil tried two modifications. The first one was to add a lock-washer to the idler bolt. The tabs of the lock washer were then bent around the bolt so that it could not easily be removed.
This wasn't the success that it was intended to be.
A further modification involved the removal of the idler arm bolt and its replacement with a socket-headed plug, which needed an allen key to remove. Whatever type of plug is in there, remember to keep your hands off it unless you are actually removing the reverse idler arm.
Drain the transmission and differentials after a run, when the oil is hot.
The capacity of the gear box is 5.5 ffice:smarttags" /><?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com
<st1:place w:st="on">US</st1:place></st1:country-region> pints or 2.6 liters.
WHAT GEAR OIL TO USE?
Most Important
Replace the lube with a straight mineral oil.... 90-grade. Under NO circumstances be tempted or persuaded to use
Hypoy/EP 90, unless you don't mind rebuilding boxes every couple of months. In <st1:place w:st="on"><st1:country-region w:st="on">England</st1:country-region></st1:place> one can obtain straight 90s mineral oil in the form of Castrol ST-90..there are others, too, such as Morris Lubricants' AG-90.
Make doubly sure it is NOT hypoy/EP. If you use straight 90s-grade mineral oil in the transmission-transfer, it makes sense to use the same oil in the differentials, too. That way, there's no chance of putting Hypoy-EP in the gearbox by mistake.
Now for the history lesson.....the Mil originally used GO (Gear Oil) and the civilian equivalent gear oil was designated "GL-!" which was a non-Hypoy/EP gear oil which did not affect the phosphor-bronze components in the transmission. After GL-1, came GL-2, -3, -4, and then 5. Each GL number represented a jump forward in technology. (Read, less wear, better protection, etc)
GL5 when it first came out had a problem with the sulphur eating up yellow metals - brass - usually used for synchro rings. This occurred only at high temperatures as the oil started to break down. The industry recognized that and the MT-1 designation was added along with additional specs requirements for GL-5. So basically gear oil with the designation "GL-5 with MT-1" should be safe for yellow metals according to current standards.
Texaco, Valvoline, Mobil all make good gear lube and it should clearly state "GL5 - MT1".
In nut shell, I have not seen any brand of straight mineral oil here in <st1:country-region w:st="on"><st1:place w:st="on">Pakistan</st1:place></st1:country-region>. There is gear oil from WARCO (1 litre tin pack with Yellow paper sticker) and the dealers claim that its a straight grade oil, but I have not tested that. What I use is a straight base oil. Its not available in any packing, so one has to buy it open as it comes from the refinery in barrels & used in power generation units & other heavy machineries. They too are two types, a Green one and a Gold one. Gold one being of higher quality so I go for that. Use the same for the diffs. Go to any 'parha likha' oil dealer and ask for BASE OIL for GEARS. He will understand. Also tell that you need an oil for the gears WITHOUT any ADDITIVES in it.
All commercial brands in the market have additives in them and these additives are sulphur based, so they eat up the yellow metals inside old / vintage gears. Castrol EP90 is a NO NO for the Mutt.
I hope this was helpful. I know it was for me ..............
