Differential Breather
How to install a rear differential breather extension
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Okay. So your differential has oil in it. Oil expands when it gets warm. Without a breather, the pressure would rise in your differential and might shorten the life of various oil seals. The stock breather is right on the differential. In the event that you should splash through a puddle that is deep enough to immerse the breather, there is a chance that your differential might suck some of that water in.
Water and oil don't mix very well and the resulting milkshake certainly doesn't lubricate very well. In the end, you have three options; 1. Stay out of the water. 2. Flush your differential any time it might have gotten wet. 3. Extend the breather. This write up is for those who choose option three.
The front differential already has an extended breather on it, coming up into the engine compartment. Some folks add a couple of feet onto it, but it's high enough to handle most moderate off road travel.
Parts/Materials Needed:
1 Toyota part number 90404-51026 Listed as a "Union" at a cost of $4.19 in January of 2002.
8 feet of 1/4" rubber fuel line
2 small hose clamps
A few nylon wire (zip) ties
Edit 01/11/05: I just got word from a 2005 Tacoma owner and he states that he did this mod on his 2005 and the same parts new work on the newest generation of Tacoma.
Edit 12/12/03: This write up remains perfectly valid, but I wanted to document something that ChrisCo and I found during my solid axle swap. Since we had to run a breather to the new front axle and since the rear diff was going to be open for gearing, we decided to check the status of the rear breather while were at it. When we cracked open the rear diff, there was a hissing sound. Once the third member was back in, we warmed it up a couple of times and cracked it again, only to hear the hissing again. It seems that the stock rear breather holds a pretty good vacuum. At least mine does. Although that is exactly what it did in the stock position, ChrisCo and I were able to come up with a couple reasons why that might not be a good thing. We reasoned that behavior was appropriate in the stock position, ON the rear axle. In that position, it's primary objective is to keep stuff out of the diff while still allowing it to exhale. Since it doesn't have any way of knowing what it's going to suck in, it doesn't. Or does so at a very slow rate. While this never caused a problem for me, I can picture a situation where you heat your axle up, then dip it in cold water. Since it's got a fairly strong vacuum inside and there is water pressure against the outside of the axle seal it's not hard to imagine what could happen. I never saw it happen, but if the seals were worn, the scenario might be even more likely.
So, we can do better. We re-ran the hose from the rear breather up to the engine compartment, up next to the one for the front diff and put a fuel filter on the end of it. Now the breather is high up in the engine compartment and if water gets that high, I have other problems. It also we allow the diff to maintain neutral pressure, breathing out AND in. I will try to get a picture soon and add it to this write up. I don't think there is any reason to stop using the stock breather, but for an extra bit of safety, the filter might be a good call.
Edit 06/20/02: Some folks have stated that their dealers can't find that part number in their systems. The secret seems to be to remove the dash from the part number. I will let you decide what that says about that parts person... So, in the event that they say they can't find the part number, have them try 9040451026 or 90404 51026. Others have mentioned that their dealer was unwilling to to order the part for them that only cost $5.00... I will again leave it to the reader to decide what that says about that dealership. In my experience, any dealer worth their salt will order any part you like, regardless of the cost. If they say they can't, they are lying.
Tools Needed:
Box/Open wrenches, 10mm and 14mm
Screwdrivers
Wire Cutters
1 cup boiling water
Estimated Time: < 1 Hour
Procedure:
Here's a shot of all the parts, with the exception of the hose.
And the stock breather on the differential housing.
Use a 14mm wrench to remove the stock breather. Use a rag to clean around the breather well before you remove it completely. Crap that doesn't get in your differential can't increase wear ;)
Use a 10mm wrench to thread the 90404-51026 Union into the differential housing. It will tighten down until about one thread is exposed.
Dip one end of your rubber hose in a cup of boiling water for 30 seconds, then insert the stock breather threads into the hose. You want to get all of the thread into the tubing. This will allow your diff to continue to breath as it would in a stock configuration and will cut down on the chances of dust or moisture getting sucked in. Secure the breather with one of the hose clamps. Some folks use VW type fuel filters on the ends of their breathers.
There are a variety of places you can vent to. Some choose to run a hose all the way up to the engine compartment, we followed the electric locker cable/brake lines up by the fuel filler neck. This view is from the perspective of the left, rear tire, looking up into the bed rail. The stock breather end of the hose was secured with wire-ties so that it was above the fuel neck. The hose was routed along the fuel filler neck, over the frame and along the locker cable.
Once the hose was routed down near the differential, we left a bend in the hose so that it would not be pulled tight when the suspension flexes. Once we had the hose secured, we cut off the excess and fitted the hose over the "Union". Secure the hose with the remaining hose clamp.
That's it. With the hose following up the filler neck, you have a good mark where you know you are safe up until. Just in case you are dying to see what the mechanism in the stock breather looks like, I will save you the trouble... :)
Enjoy.
-Rob (WATRD)