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Discussion Starter · #1 ·
What will I need to change the manual gearbox oil in regards to tools and oil. I had a local shop Change it but now shifting gears is 'notchy' and not as smooth. I was considering synchromesh; might something else be better?
 

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Do you mean Transfer Case? Or Transmission?
 

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All you need to do a flush is a socket that fits the drain plug and fill plug (sorry I don't know the size) and drain it and then fill it back up. The level you fill it to is the height of the fill plug. You pump oil back into the transmission and when it starts to come out of the fill plug then it's full. That's it. Nothing to it. I used SAE 85w-140 GL5 Gear Lubricant. I don't know what is recommended but I used this oil because it's thicker and my transmission has over 200K on it and it still shifts very smooth. I just went with thick oil because it's suppose to keep gears a lot cooler. I also use it in my differentials.
 

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The only tough thing is re-filling the trans., here is a hint I found useful, stay away from the pumps, I can spit more than they pump, and fall apart right away, get a fill hose that attaches to the bottle, they a like $5, and you can use it for your T/C and diffs as well. :thumb:
 

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All you need to do a flush is a socket that fits the drain plug and fill plug (sorry I don't know the size) and drain it and then fill it back up. The level you fill it to is the height of the fill plug. You pump oil back into the transmission and when it starts to come out of the fill plug then it's full. That's it. Nothing to it. I used SAE 85w-140 GL5 Gear Lubricant. I don't know what is recommended but I used this oil because it's thicker and my transmission has over 200K on it and it still shifts very smooth. I just went with thick oil because it's suppose to keep gears a lot cooler. I also use it in my differentials.
Yes and no! The drain bolt is 15/16" and same for the fill plug. I suggest against any GL-5 oil. It has a compound that is known to eat yellow metals! Your synchronizes are yellow metal! Synchromesh is what I used and like it others have used 10w-30 synthetic. And I found it easier to remove the shifter and shifter boot to fill my trans. The fill plug is very hard to fill at and get a accurate level unless you have a pump of some sort. But only rakes about 4 qts depending on the trans.
 

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Yes and no! The drain bolt is 15/16" and same for the fill plug. I suggest against any GL-5 oil. It has a compound that is known to eat yellow metals! Your synchronizes are yellow metal! Synchromesh is what I used and like it others have used 10w-30 synthetic. And I found it easier to remove the shifter and shifter boot to fill my trans. The fill plug is very hard to fill at and get a accurate level unless you have a pump of some sort. But only rakes about 4 qts depending on the trans.
x2 on fill strategy and synchromesh.
 

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Motors Specifications Guide specifies 75W-90 GL-5 @ 7 pints. My fill plug is a Torx socket amd my fill plug is 15/16
 

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Motors Specifications Guide specifies 75W-90 GL-5 @ 7 pints. My fill plug is a Torx socket amd my fill plug is 15/16
This may be but I am one not to push the envelope. GL-5 is supposed to have a compound build up that breaks down yellow metals. Although I don't know first hand but I'm not willing to figure it out and spend $$$ on a tranny that I could have prevented by staying away from GL-5.
 

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Discussion Starter · #11 ·
This may be but I am one not to push the envelope. GL-5 is supposed to have a compound build up that breaks down yellow metals. Although I don't know first hand but I'm not willing to figure it out and spend $$$ on a tranny that I could have prevented by staying away from GL-5.
This is why I specifically went with RP. Non-corrosive to yellow metals.
 

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This is interesting because I logged in today to ask about transmission oils. I have a 1995 Rio Grand, with the 5 speed. I used gear oil when I filled it. It was stiff shifting in the cold weather. Now in the summer it is better.
The owner's manual and the Haynes manual recommend gear oil. An old time mechanic, at a Jeep dealer swears by motor oil. He said the gear oil makes the syncros's stiff. I would love to hear opinions from you folks.

Thanks,

Mr. Leet
 

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Motor oil is awesome in these. I have used Synchromesh, and redline MTL 90. Both were a waste of money. 10W-30 High mileage Synthetic is what I stick in mine and it shift perfect. Costs about a 1/3 as much too. That is what the manufacturer recommends. As for certain Gear oils eating yellow metals, that does happen. Originally the recommendation was Gear oil, but years later they changed it to plain old motor oil. I am guessing too many failures over a long period of time since it took them years to change it.

For the sockets, they are metric, NOT SAE. If you use SAE a few times you will start to round them off since they are aluminum and fairly soft. If I remember right it is a 24mm, but I could be wrong. And make sure you remove your fill plug before your drain plug so that you know you will get the fluid back in. Personally though, I remove the shifter and funnel it in through there. Much easier and not as messy.
 

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You would think that after all the money Jeep spent on designing these trannys they would recomend what they are designed to use.I dont have the R&D money required to second guess the manufacturer. I doubt any one here does.Your best bet is to stick with the fluid it is designed for.I have been an auto tech for nearly 40 years and that logic has NEVER failed me.
 

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I use full synthetic 10w30 and it shifts great. I run parts plus brand, which I've been told is rebottled valvoline
 

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You would think that after all the money Jeep spent on designing these trannys they would recomend what they are designed to use.I dont have the R&D money required to second guess the manufacturer. I doubt any one here does.Your best bet is to stick with the fluid it is designed for.I have been an auto tech for nearly 40 years and that logic has NEVER failed me.
X2 - no use in trying to outsmart the engineers!
 
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