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The diff oil and the transmission are the same cavity, and filled from the same place. But there are two "low spots" with drain plugs. All of the plugs are 24mm or 15/16". So remove both of the plugs, on the bottom of the transmission and the differential, to drain all the oil.

I find it really ugly to try and pump lube into the down-forward facing level plug. So I remove the vent-plug in the top of the transmission, and using a hose on a funnel, run oil in the top of the transmission until it starts to piddle out the level plug. The vent plug is on top of the transmission, kind of under the air filter box. There are two plugs there, one has a vent cap on top, and the other plug is a flat-top hex. As I recall, the vent plug is the forward of the two. Do not remove the flat-top hex one, it has a dowel on it to locate the shifter mechanism. Remove the vent plug and put a hose-funnel in, and pour in the oil. Its a bit fiddly, but way less fiddly and less messy than pumping oil in the level hole.

While you're at it, check the condition of the oil cooler hoses to/from the transmission, if any fraying or cracking replace. If either of those hoses fail, without warning it pumps out all the tranny lube and grinds your transmission to dust before you know it.
 

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Hi there thanks for your help I wondered if I could just pick your brain a little bit if I take out the front diff drain plug and the gearbox drain plug and drain both out when filling the gearbox will it automatically fill the front diff if so do I put the diff plug-in while filling or do I just leave the diff plug out until oil drains out of the diff so I know the difference full and also is it the same oil for the rear diff and transfer box many thanks Gary
 

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There is alot of discussion about what oil to use, search the forum. If you are cold-climate, synthetic oil will help with operating economy. I used synthetic. The same oil can go in the rear diff. The rear diff is probably not posi-trac, so regular 85w-90 EP or synthetic willl be fine there.

The transmission cavity attached to the engine contains the main 5 speed transmission, the transfer case, center differential, and front differential. It is all one cavity, with two drain points:
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So remove both drain plugs to drain all the oil. Put both drain plugs back in and tighten. Remove the level/fill plug and put back in just a tiny bit of a turn. Then remove the vent plug from the top
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Pour oil in the top until droplets of oil appear around the vent/fill plug. Replace the vent and tighten the level/fill and you're done.
 

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Google says transmission capacity is 3.9 litres or 4.1 US qts. Note, a US qt is 0.946 litre. The transmission may have some nooks and crannies inside that do not drain from level, so it may not take the full amount.
 

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Google says transmission capacity is 3.9 litres or 4.1 US qts.
Thats correct for a 2WD manual trans. For an AWD, owner’s manual says it’s 5.3 US quarts, with the additional going in the transfer case, which has its own drain plug. They both share the same fluid as you mentioned, so filling one fills both. The rear diff takes 1.0 qt.

Automatics take 3.5 qts of Dex3. With AWD, the transfer case takes 0.7 qts of GL5 gear oil. Rear diff takes the same 1.0 qt.
 

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Thanks for the clarification BMR. 5.3 US qts translates to 5.01 litres. When I did my fluid-change, I was dumping into the vent plug from a 5 litre jug, and when it started coming out of the level plug, the amount left in my jug was below the lowest 0.5 litre graduation on the jug. So there may have been a couple nooks and crannies that trapped some oil for me, and didn't take the entire 5 litres.

When I drained mine, a bit more than 4 litres came out. I based my acquisition of replacement fluid on that amount, and bought a 5 litre jug.

Capacities aside, filling to that forward-downward facing level plug is going to get to the correct level. In my case I was dumping synthetic (thinner viscosity) in a funnel into the top vent plug. The level plug was just barely threaded onto the threads, by like a half a turn. As I got to 4 litres out of the jug, I knew I was close. I would dump in a bit into the funnel and then lay underneath looking for droplets to appear around the level plug. When droplets of oil appear around the fill/level plug, I know I have enough oil, maybe an ounce or two extra won't hurt. I tighten the level/fill plug, install the vent plug, and check it in a week.
 

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Good Day Gary, BMR and kamakeraion also contributed to this discussion, thank you to them as well.

The level plug is on the front down-facing casting of the transmission. The correct lube level is to the bottom of that plug. If you have a lube pump, you can fill through that level plug hole. I, and lots of other owner-wrenchers at home, do not have a functional useable lube pump. So I use a 16" piece of 1/2" clear vinyl hose on a funnel into the vent on top of the transmission. Here's a photo of where I stick the hose.
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As you can see, I must have been a smidgen over-filled, because some of my overfill seems to have barfed out my vent. This vent plug is a bit tricky to get to, I use a 15/16" socket, a u-joint, and a 12" extension all on my 1/2" ratchet. Crack the plug loose a turn, then get in there with an air-hose and blow away all the crud so the crud does not drop into the transmission. Then take the plug out, and stick the funnel-hose in, and pour in..

Good luck.
 

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With oil specification, 75/90 or 80/90 is referring to the viscosity of the oil at temperature. The first number is the cold viscosity, ie after your car is sitting overnight. The second number is the up-to-operating-temp viscosity.

Synthetic oil is formulated to be thinner - easier flowing - cold, and equally as thick while hot. So 75/90 synthetic flows more easily cold than 80/90 conventional. Given that synthetic and conventional are both 90, the viscosity should be equal at operating temperature.

For differentials and transmissions, the gear lube spec that is most important is film strength; that is a film of oil between the driving and driven teeth remains intact, and does not break down allowing metal-on-metal contact. Most modern gear oils have the "extreme pressure" additives to meet or exceed the EP specification.

There is a really deep and vast rabbit-hole we can get down regarding gear lube spec. Basically, get GL-5 oil; from our owners manual:
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There’s a good thread regarding exactly what oil to use in these manual transmissions here. I chose to use Redline 75W90NS. One key attribute is being synchro safe. Many aren’t.
 
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