HOW TO: Change your front/rear diff oils

[Outofideas]

I just changed the fluids on mine and it was easy. Luckily I work at a shop so I was able to use a lift after my techs were done for the day. I used 74w140 royal purple both front and rear so I'll see how good it performs for the $$. I used a quick curing rtv that is usable in 5 minutes so i did not have to wait on the rear to fill and no leaks so far. When removing the diff cover on the rear, I leave the top bolt in just a few threads when i pry the cover loose so it does not pop free and make a huge mess. When most of the fluid is drained take out the last bolt and then pull the cover free.


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[sevenhelmet]

I just read the dino/synthetic gear oil thread. Yikes. I think I'm going to just buy dino oil for both diffs now. It's cheaper than the synthetic stuff anyway.

 

[sevenhelmet]

I just picked up a gallon jug of Coastal 80W-90 "dino oil" for a steal. I'll use some of that for the rear axle, and put my leftover 75W-140 synthetic oil in the front axle.

Unless it's cool to use the remaining 80W-90 in the front diff as well... any experts care to weigh in?

If not, I'll play it safe- my Jeep's health isn't worth the risk!

@ Outofideas: Be interesting to hear about how the RP gear oil works for you. I use RP Synchromax in my transmission, and she shifts oh-so-smooth. I used Pennzoil Synchromesh once- NEVER AGAIN.

 

[first&lastKJ]

Now i'm confused on what gear lube to use.
The owners manual for our 07 says
Front 80w-90
Rear 75w-90 synthetic. For towing use 75w-140 synthetic.
Our 02 owners manual says use gear lubricant, for towing use 75w-140 synthetic and thats it.
Neither have been changed since new. Does it really matter what weight I use?

 

[tjkj2002]

Now i'm confused on what gear lube to use.
The owners manual for our 07 says
Front 80w-90
Rear 75w-90 synthetic. For towing use 75w-140 synthetic.
Our 02 owners manual says use gear lubricant, for towing use 75w-140 synthetic and thats it.
Neither have been changed since new. Does it really matter what weight I use?

If you don't tow or offroad it 80w-90 dino front and rear is great.If you tow or offroad 85w-140 dino is your choice then.

 

[first&lastKJ]

If you don't tow or offroad it 80w-90 dino front and rear is great.If you tow or offroad 85w-140 dino is your choice then.

What is "Dino" never heard of it until this post, is it synthetic, who sells it?
Yes I tow, so 85w-140 front and rear or just rear only?

 

[speedracerbubba]

What is "Dino" never heard of it until this post, is it synthetic, who sells it?
Yes I tow, so 85w-140 front and rear or just rear only?

Dino is just another way of saying conventional oil rather than synthetic.

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[tjkj2002]

Dino is just another way of saying conventional oil rather than synthetic.

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Or another way to say it is..............

$5 per qt compared to $18 per qt.

 

[theroofable]

I am having a hard time finding some dino 75w-140 or 90 gear oil. Anyone have a good place to get it, I tried online searching for it at napa and walmart but they only carry synthetic, or so it seems.

 

[tjkj2002]

I am having a hard time finding some dino 75w-140 or 90 gear oil. Anyone have a good place to get it, I tried online searching for it at napa and walmart but they only carry synthetic, or so it seems.

75w-90 and 75w-140 are synthetic weights.Dino weights are 80w-90 and 85w-140.

 

[theroofable]

Oh ok, so what I should be looking for is the 85w-140 since it holds up better. Thank you sir. Now would it be better to add the 85w-140 to the rear even if I dont do regular offroading/towing. I only do that once every few weeks, but would like to put it in anyway. HERE is some I found. Good enough? Also, do you bolt the cover back on and then wait 30mns with the rtv or wait 30mns before putting them back together.

 

[tjkj2002]

Oh ok, so what I should be looking for is the 85w-140 since it holds up better. Thank you sir. Now would it be better to add the 85w-140 to the rear even if I dont do regular offroading/towing. I only do that once every few weeks, but would like to put it in anyway. HERE is some I found. Good enough? Also, do you bolt the cover back on and then wait 30mns with the rtv or wait 30mns before putting them back together.

It's really your choice,but when you tow if you tow close to max weight 85w-140 would be my choice.

The way I do my diff covers is.........

After cleaning both surfaces,apply bead of RTV on diff cover(around all bolt holes),let sit for about 5-10 mins.Then put diff cover on and tighten bolts till you just start to see the RTV ooze out the sides.Let sit for another 5-10mins then finally fully tighten all cover bolts.Let stand for another 15-20mins and refill.Never had a cover leak from doing it the way I just listed.

 

[TwoBobsKJ]

I've always done the diff cover/RTV the way Troy describes. And like Troy I've never had a leak.

As far as the oil, as long as it says GL-5 you're good to go. And my opinion is, even though I only tow my boat about half the year and wheel about once a month or so...why not put in the 85W-140? I'm not a heavy off-roader and my boat only weighs about 1800 lbs but I'd rather be protected. Can't hurt, right?

Bob

 

[theroofable]

Yes, I would like to add the 85w-140. Same view as mine. Im not worried about rtv leaking, I use it at work quite often. What happens if it oozes back into the fill area? Do you put it on the outer part of the diff cover? I saw one on youtube where they applied it and then rubbed it to all contacting surfaces. Thanks for the help guys, I really needed to get this project on the road.
Also, when changing, just jack them up a few inches to get the right fill level?

 

[first&lastKJ]

85-140 front and rear? Or 85-140 rear only, and 80-90 front. I do tow two times a year about 1600 miles, single axel trailer about 1800 lbs.

 

[theroofable]

85-140 front and rear? Or 85-140 rear only, and 80-90 front. I do tow two times a year about 1600 miles, single axel trailer about 1800 lbs.

Uh Im pretty sure 85-140 in both. Like stated earlier, its better for them anyway.

 

[first&lastKJ]

Thats what I wanted to know. Thanks.

 

[theroofable]

I believe it says that in the first post. I could be wrong, others feel free to correct.

 

[67Customs]

My owners manual says 75W-140 only for the front and either 75W-90 or 75W-140 (towing) in the rear.

However, the Factory Service Manual says 80W-90 for the front and either 75W-90 or 75W-140 (towing) in the rear.

So, not even Chrysler gives me a straight answer.

I just go with 75W-140 in the front and rear even though it costs more. I tow quite a bit during the summer.

 

[TwoBobsKJ]

My owners manual says 75W-140 only for the front and either 75W-90 or 75W-140 (towing) in the rear.

However, the Factory Service Manual says 80W-90 for the front and either 75W-90 or 75W-140 (towing) in the rear.

So, not even Chrysler gives me a straight answer.

I just go with 75W-140 in the front and rear even though it costs more. I tow quite a bit during the summer.

As tjkj2002 explains in one of his posts on this thread the diffs are not pressurized systems and therefore the lubricant isn't forced into all areas of the differential - it is a "splash" system. The synthetic oils don't stay on the gears throughout the rotation as well as thicker 'dino' oils do - so going with a synth really isn't as good for your system as an 85W-140 dino oil.

You're spending money on a synthetic oil that doesn't do as good a job as a dino oil. Think of it this way: If it makes you feel better you could buy a gallon of 85W-140 for half the cost of a quart of full synth, change your diff oils twice as often and still save money! arty52:

Bob