jeremygibbs42 3 #1 Posted October 16, 2015 Hi, I am a new owner of a 312-8. I recently attempted to do a transmission oil change. I bought Lucas 90 weight gear oil (2 qts). I found the drain plug (allen key) underneath the transmission and broke it loose. I allowed the oil to drain and it was nasty looking. I then opened the fill plug (which I believe is to the left). I want to make sure that the fill plug is the square bolt that is to the left. I attempted to put oil back in and it seems to only let me put in less than a quart and it begins to pour out of the fill hole. When I look at the dip stick it looks completely dry. So I do not understand whats going on. I want to make sure that the fill is the square bolt just to the left when you are looking from the rear. So i don't get why i am seeing no oil on the dipstick even though it continues to pour out of the fill hole. Any help is much appreciated. Thanks Share this post Link to post Share on other sites
pfrederi 17,174 #2 Posted October 16, 2015 There is a ridge in the bottom of the tranny case that traps some oil in the front half of the tranny. You have to jack the front end up to drain it all. You said it was nasty before you put in your good oil i would but in a half gallon of DF2 (diesel fuel) or kerosene, run it around for a few minutes then raise the front end and drain it again. If it is really nasty you may have to repeat. Fill it with good oil thought the dip stick (or pull the shifter and go through that. Leave the fill plug open at first, it will speed up the filling. then close it and keep adding slowly til you get a good read on the dip stick 7 Share this post Link to post Share on other sites
oliver2-44 8,892 #3 Posted October 16, 2015 I' filled might 312-8 through the dip stick tube Share this post Link to post Share on other sites
tunahead72 2,346 #4 Posted October 16, 2015 (edited) Filling through the dipstick tube is definitely easier, you'll need a long skinny funnel to reach down there. And be aware you might not get it to take the full 2 quarts, especially if you didn't get all the old oil drained out.Your old oil was "nasty looking", as in milky or bubbly? That would indicate water got into the transmission, probably through the shifter boot. Make sure you check that too, and replace it if necessary.--------EDIT: Actually, your funnel doesn't really have to be very long, it just needs to be skinny enough to fit snugly inside the dipstick tube. If the tube has been removed for some reason, the funnel would have to be long enough to reach into the opening at the top of the transmission. Edited October 17, 2015 by tunahead72 4 Share this post Link to post Share on other sites
953 nut 52,044 #5 Posted October 16, 2015 The 312-8 is a good worker, keep it well maintained and it will give you many more years of service. 2 Share this post Link to post Share on other sites
slammer302 2,154 #6 Posted October 16, 2015 Make sure that there isn't something blocking the drain hole and not letting all the oil drain out. It has happened to me some nasty sludge built up at the drain and wouldn't let the oil drain out I poked it with a screw driver and the rest came out but still I can usually only get about a quart in one Sent from my XT1080 using Tapatalk 2 Share this post Link to post Share on other sites
sorekiwi 761 #7 Posted October 17, 2015 This photo shows why you need to raise the front of the tractor when draining the old oil, note that there is a "hump" in the middle of the case which traps a lot of oil in the front of the case. 3 Share this post Link to post Share on other sites
jeremygibbs42 3 #8 Posted October 17, 2015 Thanks guys for all of the information, i will be working on it over the weekend. If i use diesel or kerosene to clean it out, do i put it in there by itself or should i leave oil in there with it also? Can i just empty it and put kerosene in it and drive around for a few minutes? Then drain and add oil. Thanks again Share this post Link to post Share on other sites
slammer302 2,154 #9 Posted October 17, 2015 I use off road diesel the store next to my house sells it and its a little cheaper. There should be enough oil left in the trans that you can't get out so theres no need to add any and I jack it up and let it run for a little while I think this puts less strain on the bearings with the very thin fluid in it Sent from my XT1080 using Tapatalk 1 Share this post Link to post Share on other sites
sorekiwi 761 #10 Posted October 17, 2015 Thinking about it now, I dont think that square filler plug on the 8 speeds is the correct way to check the oil level.That plug is the correct level for the 3/4 speeds, when the 6/8 speed was introduced they added an extension to that hole (probably about 1 1/2 inches high) for more oil capacity. Later on they added the dipstick under the seat.On my "late model" tractors I remove one of the 3/8 bolts in the top center of the transmission (to bleed the air out) and fill the trans through the dipstick tube. I use the dipstick to gauge the level in the trans. 3 Share this post Link to post Share on other sites
boovuc 1,090 #11 Posted October 18, 2015 (Beat me to it!) If you fill to the plug on the left side of the transmission case, you are still off the stick on the hi/low trannys.Use the stick to dictate the rear oil level unless you know first hand someone "modified" the dipstick/tube. 1 Share this post Link to post Share on other sites
oliver2-44 8,892 #12 Posted October 18, 2015 If you jack it up and let it run with diesel in it put an electric header under it to heat the case, sure seems to help the diesel dissolve the sludge.One of these days, I need to write a thread about some things we did reviving old tractors at the tractor shop I worked at in my high school years! 1 Share this post Link to post Share on other sites
jeremygibbs42 3 #13 Posted October 21, 2015 Hey guys, just wanted to say thanks for all the info. I used diesel and it seemed to work really well. I also jacked up the front and seemed to get much more out of it. It took almost 2 quarts of Lucas 80-90w. Thanks again. 3 Share this post Link to post Share on other sites
callum12 256 #14 Posted October 24, 2015 I was just about to start a new post on how to clean out my tranny, seems i found it all here!callum 1 Share this post Link to post Share on other sites
