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GCUK 06-07-2013 02:53 AM

diff oil change question
You have to take the cover plate off to drain the oil out.
Is there meant to be a gasket on the cover plate ?

Some guys in the UK say they just use liquid sealant to seal it back on with and there's have been OK.

What do you do ?

Is the drain plug Imperial or metric hex drive ?


JeepFreak12 06-07-2013 05:18 AM

Re: diff oil change question
I used mopar brand RTV sealant so seal the diff cover. I'm almost 100% sure its metric (most stuff is on car's now). You should really be able to use any RTV sealant on the diff. Also depending on what t-case you have, don't forget the limited slip additive!

Frango100 06-07-2013 07:29 AM

Re: diff oil change question
There seem to be people who just suck the fluid out of the diff, but best is to remove the cover and clean it out as much as possible with a lint free cloth. Have a look at the pinion and ring gear for abnormal wear when you are in there.
Jeepfreak probably ment to say which type of diff you have, because when you have quadra drive, both diffs have a vari-lok inside it and it will need limited slip additive in the fluid to prevent wheel rub in tight turns. (also with a factory tow package it can have a Vari-lok in the rear diff only).
The diff covers are factory sealed with RTV.
To be able to remove the rear diff cover, you need to jack up the rear of the jeep, to get access to the upper cover bolts. Also always first remove or at least loosen the fill plug. It happened already to people that they removed the cover to find out that the plug was stuck in place, whereafter it was impossible to fill the diff up again.
The fill plug is 3/8 " when im not wrong, just the square of a middle size ratched. Most other bolts/nuts are metric though.

JeepFreak12 06-07-2013 08:25 AM

Re: diff oil change question
Yes I meant diff not t-case, I should have re-read what I was saying before I post it.

GCUK 06-07-2013 02:18 PM

Re: diff oil change question
Thanks for the help guys.
Yes I have Quadra dive, The manual says use the SAE 75-140 synthetic oil. Now I thought I read this has slip additive in it already ? But some say its not enough and put in some additive as well.

Any thoughts ?

Frango100 06-07-2013 05:15 PM

Re: diff oil change question
Some fluids have the limited slip in it. If you buy that one, you need to know the amount they have put in there.
You could also just put it in and drive some tight figure 8's and check that after doing that several times, that you don't get tire rub (not enough additive will result in a locking vari-lok and one of the two wheels will start skipping). If you get, then there is not enough limited slip additive in it.

JeepFreak12 06-07-2013 11:10 PM

Re: diff oil change question
When I used the diff fluid with additive in it, I had to add more limited slip additive to it because it was binding on sharp corners.

GCUK 06-15-2013 06:45 AM

Re: diff oil change question
Well I've done the front diff. castrol synth LSD oil + half the recommended additive (FM)
Having read some don't add any to lad oil, some add half and some add the full amount, I thought the half sounded good to me !
Used Loctite black silicone sealant for "surfaces in permanent contact with oil". Seems the best quality, and as the previous stuff is leaking after 10,000 miles I hope it lasts better.
Now for the rear. Jacked up, but still not a great deal of room to work, not sure I'll get my torque wrench onto the top bolts when it goes back together.
Ah well, back to work.............

Frango100 06-15-2013 08:14 PM

Re: diff oil change question
I didn't bother using a torque wrench on those bolts, a ratched fits ok.
Regarding the additive, you better don' t use too much. The additive changes the oxidation properties of the fluid negatively, so the less which works, the better.

GCUK 06-16-2013 04:59 AM

Re: diff oil change question
Just done the back diff. Had to drop the sway bar to (Addco) to get the cover plate off. All nice and clean inside. Refilling is a pita !!
Again put half the FM in and see how it goes. When people say the diff "locks up well" after adding FM what do they mean ?


Frango100 06-16-2013 06:49 AM

Re: diff oil change question
The problem normally is that the vari-lok will lock when making tight turns, causing one of the tires to skip on the pavement. Difficult to tell what an other means with " locks well" after adding the additive, because the additive should prevent full locking (to prevent the wheel skip during tight turns). Did you make several figure 8s already (as tight as possible), to get the new fluid inside the vari-loks? If after/during these figure 8s no skipping occurs, the additive percentage should be ok.

GCUK 06-17-2013 05:28 AM

Re: diff oil change question
No figure of 8's yet (can find a open area to do it nearby !) But lots of tight circles, and reversing on full lock, where i used to feel the tyre "snatch" and release a bit.
All OK so far................ :thumbsup:

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