ARB RD23 Lockers + Oil

[DaveInDenver]

Trying to determine the right level of gear lube in my back axle to hopefully stop it from working its way back up my air lines. I still only have the stock sized breather, going into a extended line and VW fuel filter, so it would seem that I need to drill and retap the breather for something larger.

But one of the things ARB recommended I do is lower the oil level a bit. So I'm just wondering about where other people are filling their axles up to. I'd hate to underfill the axle and cause bigger problems cooking the pinion or ruining the R&P. I filled to a point that seems about 1/2" below the fill hole, which is about 1.5 quarts. Seem about where other people are?

 

[BajaXplorer]

Chris (Baja) had a similar problem with the front. He will probably have some info when he sees this thread.
BX

 

[Grim Reaper]

Be careful on the filter you are using. Some have a back flow valve. I could see a back flow valve causing oil to get pulled up into a line.

I have never had a issue with any of the vehicles I extended the lines on but I was careful on my filter selection. The diameter should not be a big deal. Its not moving much air at all.

I suspect that ARB recomends lowering the "volume" of oil. Their case takes up more space so it would stand to reason that you would lower the volume of fluid something 1.3 quarts verses 1.4. The level at the hole would stay the same but its less actual oil.


I would be hesident to run a lower oil level especialy in a high pinion application out of fear of starving the pinion bearings. Less oil also means less thermal mass to disipate heat. Important on the gearing in a toyota.

 

[BajaTaco]

Yep, I have had similar issues with my ARB in the front diff (IFS diff) on a few occassions. And I think Scott has too - and others. Basically, you are correct, if you fill right up to the fill opening, it will over-pressurize when it gets hot and you use the locker. Except, I have also had an instance where it happened and I wasn't using the locker. I was in Mexico just doing some fairly fast dirt in 4-hi (and it was at night - not hot outside). In this case, I had filled to the opening (which was too much). I have since tried to fill only to about 1/2" - 3/4" below the fill opening and that seems to work. I recently had another "puking" episode earlier this year, at an extreme angle of a climb up a rock ledge. I either goofed and overfilled (I was on a slanted surface when I changed gear oil) or it was just too much angle - I'm not sure. I did have the locker engaged.

Whether filling short of the opening will do damage or not, I have yet to find out. I don't anticipate a problem. Lars Dennart has some really good commentary on this in his RD-90 install article...

"There have been several issues of gear oil being blown out of the front breather using ARB lockers. There are several things that contribute to the problem. Here are my conclusions.

• The breather is too small.
• The breather is too low.
• The ARB is a 4 pinion carrier displacing much more than the stock 2 pinion. The amount of oil should be adjusted downward.
• The ARB carrier is enclosed and that oil could easily be carried over its surface to the top of the diff housing where the breather is. Basically a wave effect. The two pinion has a big hole in the middle. This could be aggravated by the strange angles the truck is sitting at when I really need that locker.
• Toyota may have the fill plug too high. Filling to the hole's bottom puts oil almost over the top of the axles.
• Any dips in the breather line will catch oil and clog the breather system.
• Oil foaming is possible but unlikely.
• It is interesting that I can cause blowout from the breather at the moment I engage the locker though. At first I thought I had a bad seal, but the compressor doesn't cycle. Maybe it leaks air while it transitions states.

I mitigated the problem by filling the gear oil to between 1/2" and 1" below the bottom of the fill hole. I then added a second breather. See Toyota Extended Axle breathers These steps shouldn't be necessary if your ARB and breathers are working optimally. I have since solved those issues."

Text is taken from Lar's website - FULL ARTICLE HERE

 

[DaveInDenver]

Well, since I fill both of my diffs to the hole and both are spitting oil, might be connected. I have the RD90 in the front and the RD23 in back, BTW. I think I'll leave the level about 1/2" below the fill plug and see what happens.