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Discussion Starter · #1 · (Edited)
I know the topic of dirty rear diff oil has come up before, however, my FJ was built 07/07 (previous posts where mainly 06 production) and she only had 8000 mi. on her when I made the switch to royal purple.

I have a had a few water crossings, but nothing I would call extreme.

The oil was milky, with a great deal of sludge/metal shavings on the magnet.

pretty gross for such a new rig.

UPDATE
I wanted to update this post for those that might be looking for info on changing their fluids. I will attempt to condense some of the info found on the following pages:

Changing your oil in the front and rear differentials before the recommended mileage, seems very beneficial, and necessary.

many members recommend changing it as soon as possible, , even as soon as 500 miles.
If you cross water, it can enter through the breathers, located at the top of each diff.
The water can cause severe damage, so changing the oil is recommended after water submerging. you can check for water contamination via the fill holes, simply by visual inspection; use a small tube to remove some, check for milky/whitish color.
do the breathe mod: http://www.fjcruiserforums.com/forums/4x4-off-road-tech/29229-scuba-driver-transmission-transfer-case-rear-differential-e-locker-breather-mod.html

the bolts on the rear are 24mm or 15/16"
the front is a 10mm allen wrench or hex socket
you are supposed to change the washers out each time you change the oil.
I have never had a problem picking them up from a dealership, I think the cost 40 cents. I also bought some spare bolts, in case I strip one (again)

oil grade is GL-5, 75w-90 (a small amount of debate on this, but thats what my manual says) others say 80w-90

synthetics are general preferred by all
some top brands you will see mentioned are:
Royal purple Royal Purple Consumer Products
mobile one syntheticMobil - The Oil That's Changing Oil
amsoilAMSOIL - Synthetic Oil, Motor and Engine Oil, Lubricants, Air Filters, Oil Filters and Greases
and redlineRed Line Oil

rear takes 3.1 qts
front takes 1.5

torque:
rear 36 ft*lbf
front 26 ft*lbf
here are the instructions View attachment diff oil change.pdf

oh and do the breather mod!!
 

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I know the topic of dirty rear diff oil has come up before, however, my FJ was built 07/07 (previous posts where mainly 06 production) and she only had 8000 mi. on her when I made the switch to royal purple.

I have a had a few water crossings, but nothing I would call extreme.

The oil was milky, with a great deal of sludge/metal shavings on the magnet.

pretty gross for such a new rig.
The diff oil should be changed at 500 miles after purchasing the vehicle, IMO. When we do ring/pinion or diff work, we suggest changing after 100 miles or so to rid the diff of any metal shavings from break-in of the new components. Most ring/pinion mfgrs recommend the same. So it's no wonder there was a lot of crud in your diff. Regarding the milky consistency, that's a pretty good indicator of water mixing with the oil, and should be changed ASAP if you see that.

And a side note, diffs, transfer cases, and manual transmissions do not have to wait to switch to synthetics, as is suggested for the engine due to piston ring seating. The sooner the better in any type of manual gear box or diff...
 

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I need to do mine badly..... How much oil do i need to put in and what type? A certain type of royal purple?
~3.1 qts of 75W90 synthetic for the rear diff. It's all in your manual (if you have one).

DEWFPO
 

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The diff oil should be changed at 500 miles after purchasing the vehicle, IMO. When we do ring/pinion or diff work, we suggest changing after 100 miles or so to rid the diff of any metal shavings from break-in of the new components. Most ring/pinion mfgrs recommend the same. So it's no wonder there was a lot of crud in your diff. Regarding the milky consistency, that's a pretty good indicator of water mixing with the oil, and should be changed ASAP if you see that.

And a side note, diffs, transfer cases, and manual transmissions do not have to wait to switch to synthetics, as is suggested for the engine due to piston ring seating. The sooner the better in any type of manual gear box or diff...
cruiser larry, i was wondering now soon to roll 20,000 , about 14,000 i had the dealer change mine it was real dark no water . ok that said i just recently changed mine over to 75 90 mobil1 synthetic. so do you think if i change it now every 10,000 that is overboard. or should i now go the full 15,000 inbetween thx
 

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~3.1 qts of 75W90 synthetic for the rear diff. It's all in your manual (if you have one).

DEWFPO
I just bought 3 qts of Royal Purple 75w-90. Is it going to be enough given that I probably won't drain that .1 out? Has anyone needed a forth quart?
THANKS
 

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cruiser larry, i was wondering now soon to roll 20,000 , about 14,000 i had the dealer change mine it was real dark no water . ok that said i just recently changed mine over to 75 90 mobil1 synthetic. so do you think if i change it now every 10,000 that is overboard. or should i now go the full 15,000 inbetween thx
I change mine every 10,000 miles and use Mobil 1 synthetic. It's just what I do. Your results may be different.

Scuba Driver mod -- It's a $30.00 mod and it can save both your rear differential and your e-locker. Unless you're just driving it on pavement as a commuter or you're picking up the kids from school, this mod is a must-do.
 

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Discussion Starter · #11 ·
The diff oil should be changed at 500 miles after purchasing the vehicle, IMO. When we do ring/pinion or diff work, we suggest changing after 100 miles or so to rid the diff of any metal shavings from break-in of the new components. Most ring/pinion mfgrs recommend the same. So it's no wonder there was a lot of crud in your diff. Regarding the milky consistency, that's a pretty good indicator of water mixing with the oil, and should be changed ASAP if you see that.

And a side note, diffs, transfer cases, and manual transmissions do not have to wait to switch to synthetics, as is suggested for the engine due to piston ring seating. The sooner the better in any type of manual gear box or diff...


I agree, it should be changed early. I think the owners manual says first change at 30,000? I am very suprised I got water in there, I would have thought with the way the breather is designed, and what IMO, have not been any extreme water crossings (nothing more then across some creeks)
I have got to do the scuba mod, and now I'm worried about the front....
 

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It's easy to inspect your diff oil. Just take the Bolt out and insert a clear plastic tube and push it in and put your thumb on the end and take it out. You will have a tube of lube to inspect and see if you have any contamination from that last water crossing you did. HTH.
Just make sure your rig is level :)
 

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Can someone tell me the socket size for the 2 bolts for the rear diff oil? I was going to change mine today but realized that I don't have socket big enough.
24mm or 15/16"

DEWFPO
 

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On the topic of gear oil, don't pay attention to the manual that calls for a straight SAE 90 gear oil. A TSB came out in November of 2007 that mandates a synthetic 75W-85 gear oil, which is apparently the factory fill since November of 2007

Not sure where you can find a synthetic 75W-85 GL-5 gear oil, although that is a common light duty manual transmission viscosity. A synthetic 75W-90 will work fine

Some forum members have asked where I was able to get my pails of Mobil Delvac Synthetic 75W-90, as they can't find it locally. The Delvac is a heavy duty synthetic, you'd typically use it in a highway tractor like a Kenworth.

Mobil Delvac Synthetic Gear Oil 75W-90, 80W-140

It's a very robust gear oil, and when you buy a pail it's cheaper on a per-quart basis than RP or M1 Gear Oil

Mobil has a search that allows you to look for commercial bulk oil depots that carry their heavy duty products. If you live in the US you can enter a zip to search

Exxon Mobil ChannelPartners
 

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I had all the oils in my FJ changed last weekend, the rear diff oil was blacker than black.

The rest looked good but changed them out to synthetic anyway.
 
G

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Just swapped out my gear oil today with Mobil 1 synthetic...that stuff was $9.00 a bottle!

I made the dumb ass mistake of try to see how I could angle the bottle into the filler hole and the little blue cap fell into the diff! :flame: I had visions of dropping the drive shaft and taking apart the rear end just to fish out that blue cap. :mecry: However I got lucky by filling up the diff with the old gear oil and it flushed right out once I removed the drain plug.

How did you guys fill up the front diff? It was tight in there so I had to jerry-rig a long plastic tube to fill it.

-B
 

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How did you guys fill up the front diff? It was tight in there so I had to jerry-rig a long plastic tube to fill it.

-B
I just changed my front diff yesterday. It's real easy, just drop the rear skid, there are 4 12mm bolts at each corner. Remove the filler plug FIRST, then the drain plug. I jacked up the passenger side of the truck to let all the oil drain.

To refill, I started on the front diff, worked back to the transfer case, then to the rear diff. I did this because I bought 6 quarts of Mobil 1 75W-90, so I could squeeze about 1/3 of a quart into the front diff at a time. I then opened a new bottle, squeezed in another third, and so on.

I do have a pump for this but, since I did a complete change of all gear oil, I didn't need to use it (plus I was lazy and didn't feel like cleaning it afterward).
 

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Just swapped out my gear oil today with Mobil 1 synthetic...that stuff was $9.00 a bottle!
Holy s***! On a per litre basis, my pail of Delvac Synthetic cost $5.50

I made the dumb ass mistake of try to see how I could angle the bottle into the filler hole and the little blue cap fell into the diff!
I'm sure all of us have done it, or something similar to it. Just laugh it off and move on

How did you guys fill up the front diff? It was tight in there so I had to jerry-rig a long plastic tube to fill it.
Since I buy my gear oil in a 20 litre / 5 gal pail, I have a pail pump. So it's very easy for me to quickly fill the front diff. Otherwise, if you're using 1 qt bottles, that long plastic tube thing is about the only way I've been able to fill an awkward location
 
G

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I just changed my front diff yesterday. It's real easy, just drop the rear skid, there are 4 12mm bolts at each corner. Remove the filler plug FIRST, then the drain plug. I jacked up the passenger side of the truck to let all the oil drain.

To refill, I started on the front diff, worked back to the transfer case, then to the rear diff. I did this because I bought 6 quarts of Mobil 1 75W-90, so I could squeeze about 1/3 of a quart into the front diff at a time. I then opened a new bottle, squeezed in another third, and so on.

I do have a pump for this but, since I did a complete change of all gear oil, I didn't need to use it (plus I was lazy and didn't feel like cleaning it afterward).
Quick question....where is the drain plug for the transfer case? I tired looking at the FJ factory manuals and it doesn't show where its located.

-B
 
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