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85 Nissan 720 4x4 transmission fill and drain plugs.


Thomas Perkins

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I will need to take the part off in front of the fill and drain plug so I can get them off.Look at the picture.I am scared that if I do that,the holes wi not line back up.If you have a 85 4x4,take your skid plate off and you will see what I am talking about.

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Edited by Thomas Perkins
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Here is a picture from my FSM manual.Here is what you have to remove to get a breaker bar on the fill and drain plug.It shows everything removed when removing the plugs.A lot to it to change the fluid.Like a job.FSM really does not tell you a thing.Just shows you how to remove the differential.Does not tell you what it actually takes to change the fluid.Get under your 4x4 and you will see what I see.Going to put this task on the back burner.Looked all over the internet and no one shows how to do it.The pictures in the book don't show everything as to my pics that I posted of my front differential.

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Edited by Thomas Perkins
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I did mine before I had my big impact and I think we ended up with a jack on the end of the breaker bar. Some breaker bars these days cant handle the abuse of some old ones. I have put a 7ft cheaper pipe and lifted myself up breaking old bolts loose with my ancient 3/4 craftsman bar. I didn't have to pull the front diff carrier at all on mine.

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On 2/2/2025 at 8:57 PM, ElliotV said:

yep had this issue before pulling steel bolts out of a aluminum waterpump housing on a 2in trash pump so I could stick the motor in a garden tractor. Had to heat the bolts then beat the crap out of them then heat them for a few more minutes with the propane and then finally hit them with the impact and all the corrosion just came out as a cloud of dust. Aluminum to steal corrosion is the whole reason my f350 wont be getting new exhaust manifolds or a new dipstick tube till I have another truck to tow heavier stuff or I blow up the motor even though the manifolds are cracked and the dipstick is held together with jb weld and fencing wire its not worth the effort. 

Didn't know the cases were aluminum. About all that helps is heating the plugs HOT, with oxy/acetylene or propane torch to expand them and loosen the corrosion. Need helper for fire watch too. Need to get clean around it as possible so there's less oil to burn. I made a vacuum jar for sucking oil. Used a standard canning flat so's to work with whatever size jar. If you can, get the fill plug out and suck the oil out and leave the drain in if ain't leaking. Going back I'd clean the threads with a gassy little steel wire brush and use PTFE pipe sealer.

https://www.amazon.com/Forney-70471-Plastic-Handled-Fitting/dp/B003YDLXQK/ref=sr_1_5?crid=37I3HUCPF64VA&dib=eyJ2IjoiMSJ9.KIYCbmito5yu2HCLY_HxOq8ubIVx28h4Akiew0ZYpJ-rgIH_VAwBOVybVEH0WCd6L02rVeYBEuuuhqYJcJ7iRKuuy6YLKCaxI2x3XiMsXvvBqUdP3d1UFkSK1pmV_Cxq8s2sROdzhgnoLvzg-mYaQD5nkZlTn5jQQolXFzFtf_BWmp0BLytO352HJswmYRG1tlRMwyh3IaDUG4fj6ONmff_LeB8Wg46T6DwKC_1etQc.MSxIjXaIsC_x2_7eJQbZRGFNbddmomPAldXLqFP_3Lk&dib_tag=se&keywords=wire%2Bpipe%2Bbrush&qid=1738666399&sprefix=wire%2Bpipe%2Bbrush%2Caps%2C199&sr=8-5&th=1 

 

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Aluminum expands twice as much as steel, though it's an extremely small amount on a bolt, but repeated heating on an aluminum case around a bolt may help. Not much good if filled with oil inside though. On studs with nuts that are seized (and the stud begins to twist and you just know it's about to snap) heating the nut cherry red  before trying to loosen is amazing. Heating the metal around a stud will expand the hole making it easier to remove. It squeaks when turned.

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I got my Redline MT-90 gear oil today,but not the rachet breaker bar.The square end looks like it won't fit tight in the square hole.Dwayne,when I remove the front part of the front Differential,then I can get my breaker bar on them plugs.I will get them off with ease.I will start on my transfer case this weekend.I will take pictures.Weather here is almost 80 in Georgia.

Edited by Thomas Perkins
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I Bought 2,that I mentioned here,and the square head is smaller than the breaker bars square head and does not fit tight in the square plugs.I will strip them out.Bottom line is as I said,I will have to remove what is in front of the differential and then I can get my breaker bar on it.Then It will come off.I had to work over time today.My work schedule is M-F 10 hour days but have been working 12 hours  on Fridays.So if I am off Friday I will get started on the transfer case,then the front differential.The FSM is no help in instructing on taking the stuff off to get to the plugs.Picture does not even look like mine.I guess no one reading this has ever changed there fluid in there's.I even looked in my Haynes and it is no help.Looked on internet and found nothing.My FSM shows it being changed with the front stuff removed.Book is not good to me.I will take pics to show what all is involved.

Edited by Thomas Perkins
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I did all the fluids when I first bought my truck I believe we used a impact 1/2" extension when we did the front diff and had to use a jack on the breaker bar and never removed anything other than the skid plate. I would start spraying it everymorning before you leave for work with your favorite flavor of penetrant. I will say that I have used the harvest king penetrating lube and it really does work and its cheap which is nice because I use a lot of it. 

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Working to much.Going to get on it next weekend.Worked 14 hours today.I will work 10 on my off day tomorrow.Not young any more.Auto Insurance went up big time here in Georgia.600 more a year. We have the highest in the nation. I pay it every 6 months ,was 1200.now is 1500 for full.coverage for 2 venicles.Alabama is high too.

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Here is what is going in my transfer case.What I have been using in my transmission for 8 years when I got it in 2017.I got the fluid from O'Rielly"s for 23.89,only took a day to get it.It is GL-4.Get the pump from Harbor Freight.I cleaned up the skid plate and have a primer coat on it.It was gunked up bad.It is hanged from a Pecan true.

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Edited by Thomas Perkins
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Thanks NC85ST.This a job.The gear oil was leaking on the skid plate and on the shaft ,causing the shaft to splatter it everywhere.This has been going on for many years.I had to take off another cover so I could clean under it.I am full of grease.I have both covers painted.I just got the fill plug off with a breaker bar and a 8 lb sledge hammer.It did mess up the fill plug.Kind of stripped,but is useable.I will see if one of my transmission plugs will work.I now have to get the drain plug off.I did soak them over night with WD-40.I will show pictures soon.

 

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