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How to fill Transmissions

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Here's my method.

Buy the appropriate oil which is most likely going to be GL4 gear oil. I had the choices of GL5 or Napa brand multi oil. It is supposedly YELLOW METAL SAFE and this is what you want. Do not use GL5 in a GL4 specified transmission. I used 3 quarts and it held almost all of it.

 

My example is a 5 speed from a Z installed in a 620. 

 

Jack up your vehicle from the drivers side. Please, use a jackstand. 

 

Remove drain plug from bottom of transmission. You may want to or have to spray it with your favorite penetrating oil first. In this case the drain plug is removed with a 1/2" drive ratchet. You should probably place something under it like a drain pan. 

 

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Give it a few minutes to drain then clean the threads of the plug and plug hole before replacing plug. It needs to be tight but be careful not to strip it. Don't worry if a couple of threads still show. Just make sure it's good and tight. 

 

 

Next you need to remove the fill plug. This is located at a 90° angle to the drain plug on the drivers side of the transmission. It is probably going to have a large square head. In my case I had to soak the plug with penetrating oil multiple times. A large adjustable wrench can be used. I used a 3/4" wrench and a 2 foot breaker bar to remove mine pushing both feet against the crossmember and cussing profusely. If this doesn't work, give it another coat of penetrating fluid and go drink a beer while the blood returns to your hands. 

 

Now for the fun part! Some people have special pumps and devices for filling the transmission. I suggest getting creative.

My technique is get around 4'~ of small hose. I used fuel line. Place one end of the hose into the fill hole of the transmission. You should be able to put it in and push it towards the back of the trans a few inches to keep it in place. Run the hose over the exhaust, torsion bar, etc. so that it comes out above the drivers side tire. Remove any seals on the gear oil bottle and cut the tip off. Insert the tip into the hose snugly so it will not fall out. At this point you can squeeze the bottle for a day or two or let gravity do it's thing. Add fluid until it runs out of the fill hole. Replace the fill plug, don't strip it. You may want to use anti seize. Here's my setup-

 

I put an oil filter wrench under my door mirror. The bottle us suspended by a screwdriver through the handle, your oil might not have a handle. Poke a hole in the bottom of the bottle to help the flow.

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Enjoy your freshly filled transmission! 

 

 

Please share any methods here. 

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(I just realized I'm a moron lol) If you jacked up your PASSENGER SIDE, your transmission will take more oil than it ordinarily would, so leave the fill plug out when you put it back on all fours, and let it drain out the excess. However you did the driver side so I suppose you might have less oil than max.
With my Z, that was the easiest route for access to the plug, as it is on the right side of the car.
For a Z, I found the easiest way to fill is just run the hose through the engine compartment, then use a funnel to feed the fluid. (I just did this a day or two ago lol)

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Car or truck always needs to be level when draining/filling. On my z I use the same method davies. 1/2 clear tubing seems to work well. I dont use a funnel though it takes too long, just jam the hose onto the bottle and squeeze, its much faster. Fill until it spills out and always make sure you can remove both the drain and fill plugs prior to actually draining. Its pretty common that people drain the trans and cant get the fill plug out. Then you have to break your balls filling from the reverse sensor. 

I usually just have my helper fill the trans because I find it tedious lol. 
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I just use a drill with a fluid moving pump and two clear hoses that fit the garden hose fitting barbs.

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Good idea with the LONG hoses, I have never thought of that!

 

I used a pump machine (BG) and multi-manufacturer 80w90 gear oil (GM Delco Sycromesh) to fill my differential and transmission last time about a year ago. Machines are nice! The machine can suck out the old too, but I like to drain it instead to insure all old stuff is gone. I wasted some old BG fluid and pumped it through to flush prior to filling.

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If the transmission was removed, always replace the rear seal. It's cheap (about $3-5) insurance against a dry and destroyed transmission. If when changing the oil or just under the vehicle and you see wetness at the rear of the tail, pull the driveshaft and replace the seal as soon as you can. At the least check the oil level as you never know how long it's been leaking nor how much oil has leaked out.

 

Standard transmissions should have their oil drained and replaced every 30K miles!!!! Many owners never keep their vehicles that long and second owners are notorious for not keeping up with necessary fluid changes. If your truck or car has 100K on it what's the chance that it still has the original oil in it???

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I use a short length of garden hose. Fills faster with larger diameter. In the colder months I keep the gear oil in the house, nice and warm so it flows faster also.

 

I run the hose down beside the motor near the steering column and use a dolla store kitchen funnel pushed in the end. From here you can see it over flow when full. The larger hose also is better to hold the oil in while you climb under to put the plug in.

 

BTW

The 71B 5 speed holds 2 liters or 4 1/4 US pints, the 4 speed is less. Over filling will just cause the oil to leak out of the breather or rear seal. How will you know if it's from over filling or a leaking seal? There's no gain to over filling. 

 

Wipe the fill and drain plug off and spray clean with brake cleaner so you can check later for any signs of leaking. If the tail is wet with oil wash it clean also so you can see if it's still leaking or when it begins.

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@240 I drained it down but jacked it up to fill it because I saw it in one of Mikes post. You can get more in it that way. Should have stated that but mainly I just wanted to post the picture ollz. 

 

For real though. You just set the bottle up and let gravity do the work for you. I put one in and went and had lunch. Came back to put the other in and played a game of league. For the third I placed a clean coffee can under the filler to catch the excess and went for a walk. 

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Over filling probably won't hurt anything. May just waste oil.

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Its a waste of efficiency too. Over filling increases windage and in turn heat and lost power for no good reason. Trans should be filled to spec. 

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Mike is like the walking datsun transmission bible, if he does it then its fine lol. Anyone else and its wrong though. 

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I heard that once a car hits something like 100k its bad to change the tranny fluid? Because its all gunked up in there and new fluid is gonna make old reminents turn hard like rock or something. Idk. Anyway what fluid should i use for my 83 Sentra five speed? Tranny fluid or just regular oil?

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That was some horrible advice you got there.

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Valvoline has gear oil that says it's safe to use where GL-4 is specified, so that's what I used. 75w-90 I think. I used a penis pump, uh, I mean 1qt bottle pump to fill it from under the car.

 

Also, YOU SHOULD ALWAYS REMOVE THE FILLER PLUG FIRST!!! Don't drain the trans to find out you can't get the fill plug out. Same goes with the rear end.

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I heard that once a car hits something like 100k its bad to change the tranny fluid? Because its all gunked up in there and new fluid is gonna make old reminents turn hard like rock or something. Idk. Anyway what fluid should i use for my 83 Sentra five speed? Tranny fluid or just regular oil?

 

Standard transmissions should be changed every 48 months or 30,000 miles. At 100,000 miles it should be on it's 3rd change of fresh oil. Most owners may have kept their truck over 4 years but each successive owner has paid less and less for it and therefore has less investment to protect. Maintenance usually suffers and oil changes extend. If you buy an old Datsun and you don't have a record of when fluid changes were done you should have them done yourself as they are likely way over due.

 

Always use API 90W GL4 gear oil. Do NOT ever use GL5 differential oil. Any transmission oil used must be compatible with copper alloys and have a GL4 rating. Yes, 'they' will tell you that GL5 is superior at protecting gears than GL4, (and it is) but what makes it superior is the thing that makes it incompatible to copper alloys (used in the bronze synchronizer rings) in your transmission.   

 

 

 

FWIW...automatic transmission fluid is capable of 100,000 miles and more between changes. The big problem is heat. Excessive heat breaks it down over time but towing (a big no no) and abuse are the biggest causes of premature failure.  If you tow or stop and go in the heat get the largest in line trans cooler you can afford and check the fluid often for color changes.  Replace every 30K minimum or oftener. 

 

The Datsun automatics have a trans cooler in the bottom of the radiator that is a joke. I've cut them open to find a 4-6" length of pipe joining the two coolant pipes from the transmission. I always run an external cooler in front of the rad. The early 510 Borg Warner 35 automatic has only fins on the torque converter for cooling and screened openings on the bell housing for venting.

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They're referring to more recent automatic transmissions. 'Flushing' a high mileage automatic can be catastrophic. Garbage in the trans can get knocked loose and clog the valve body/passages/etc. 

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Ok cool guys! Thanks for the clarifications!

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Standard transmissions should be changed every 48 months or 30,000 miles. At 100,000 miles it should be on it's 3rd change of fresh oil. Most owners may have kept their truck over 4 years but each successive owner has paid less and less for it and therefore has less investment to protect. Maintenance usually suffers and oil changes extend. If you buy an old Datsun and you don't have a record of when fluid changes were done you should have them done yourself as they are likely way over due.

 

Always use API 90W GL4 gear oil. Do NOT ever use GL5 differential oil. Any transmission oil used must be compatible with copper alloys and have a GL4 rating. Yes, 'they' will tell you that GL5 is superior at protecting gears than GL4, (and it is) but what makes it superior is the thing that makes it incompatible to copper alloys (used in the bronze synchronizer rings) in your transmission.   

 

 

 

FWIW...automatic transmission fluid is capable of 100,000 miles and more between changes. The big problem is heat. Excessive heat breaks it down over time but towing (a big no no) and abuse are the biggest causes of premature failure.  If you tow or stop and go in the heat get the largest in line trans cooler you can afford and check the fluid often for color changes.  Replace every 30K minimum or oftener. 

 

The Datsun automatics have a trans cooler in the bottom of the radiator that is a joke. I've cut them open to find a 4-6" length of pipe joining the two coolant pipes from the transmission. I always run an external cooler in front of the rad. The early 510 Borg Warner 35 automatic has only fins on the torque converter for cooling and screened openings on the bell housing for venting.

 

 

They're referring to more recent automatic transmissions. 'Flushing' a high mileage automatic can be catastrophic. Garbage in the trans can get knocked loose and clog the valve body/passages/etc. 

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I use an oil  pump from a 280zx turbo rear diff, it was left over from when I did my l28et turbo swap in the S30. 

One hose goes in the bottle, the other one in the filler hole.

It got power from a spare battery but that was too cumbersome so I chopped the wire and lighter plug off a cheap car vaccum cleaner so now I just pop it in the cig lighter, ignition on and the transmission fills up :)

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I use an oil  pump from a 280zx turbo rear diff, it was left over from when I did my l28et turbo swap in the S30. 

One hose goes in the bottle, the other one in the filler hole.

It got power from a spare battery but that was too cumbersome so I chopped the wire and lighter plug off a cheap car vaccum cleaner so now I just pop it in the cig lighter, ignition on and the transmission fills up :)

 

The zx turbo rear end (or any other) does not have an oil pump.

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On a 720 p/u.....I drill a 1-1.5" hole about where your heel sits(gas pedal) in the trans tunnel. Easy to patch/plug(I use an extra factory floorboard drain plug). A 6" chunk of 3/8 fuelline will fit onto the 'squirt' top most gear oil bottles have. Whole lot easier than pumps/long fill tubes or on your back underneath. Synthetic gear oil is a GOOD idea. You will notice an increase in mpg due to lower viscosity....I have used Redline MTL under the most extreme/abusive conditions and have had zero problems.

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Well you have to get under it anyway to get the bung loosened and removed and then replaced so not a 'stretch' to shove a hose in the hole for filling. As to a 3' garden hose.... even thick 90w will gravity feed quick enough and you don't have to squeeze and hold the bottle.

 

I like synthetic but what I don't like is it being so slippery it will wet a worn rear seal that will hold 90w without a problem. Synthetic is often that way in older Datsun transmissions and differentials. It will leak where 90w won't. The fix is a new seal or replace with 90w and wash the oil off. I've had this happen at least twice. I always replace the rear seal any time the transmission is out or driveshaft off.

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Well you have to get under it anyway to get the bung loosened and removed and then replaced so not a 'stretch' to shove a hose in the hole for filling. As to a 3' garden hose.... even thick 90w will gravity feed quick enough and you don't have to squeeze and hold the bottle.

 

I like synthetic but what I don't like is it being so slippery it will wet a worn rear seal that will hold 90w without a problem. Synthetic is often that way in older Datsun transmissions and differentials. It will leak where 90w won't. The fix is a new seal or replace with 90w and wash the oil off. I've had this happen at least twice. I always replace the rear seal any time the transmission is out or driveshaft off.

If the seal leaks due to the lower viscosity.....seal was junk already and waiting to fail. U will find though....u can't pause as long between gears because 'thinner' oil does not keep syncro spinning as long. May have 2 double clutch/fully depress pedal 2 achieve smooth shifts from r to 1st, 2nd -1st etc. I only use the clutch pedal for about 60% of my gear changes....I know how to match rpms to the gear I want. If you are not careful clutch-free shifts can wear syncros. Grew up around non-syncro mesh old Chev trucks/early vee-dubs.....

 

Seal is cheap....easy to swap out. Replace it & be worry free!

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