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Rear Differential Breather Vent Mod

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DL175

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Discussion starter · #1 ·
I decided to do this mod since my rear differential breather vent was rusted.

The rear differential breather valve or breather cap sits on top of the rear differential. It is pressed in and spring loaded. Hot air from the rear differential vent through this breather valve. You can check the condition of the breather valve by first jacking up your car or using ramps. I found the driver side was easier to reach over the top of the rear differential to check near the rear differential drain plug. There is very little room on the top but just enough room for your hands to feel the valve. I can feel the valve was rough and not movable. I can't see it but I am sure it was rusted. There was no road crud that I can feel. The problem with a rusted breather valve is that it could crumble if it is loosen. Another problem is that a stuck breather valve will eventually blow the seals and cause a leak in the rear differential. I decided to create a new breather valve from the fill plug.

Here is a picture of the rear differential breather valve:
154760


Here is the parts I am going to use for my new breather mod:
  • 9 feet of rubber hose (3/8 inch) rated for oil/fuel. If you want something stronger you can use transmission hose for higher heat.
  • 2 hose clamps. I used 5/8 stainless steel hose clamps from here.
  • 1 hose barb fitting adapter. Size M18 x 1.5 to 3/8 (9.5mm) from here. Amazon sell them if you want to pay a bit more and get it quicker.
  • 1 vent valve. I got a Dorman 924-284 bought here, but there are many alternative valves you can use.
  • Hardware to mount valve. I did not buy my mounting kit. I used what spare parts I had around.
  • Cable ties
154761


So lets get started and go to the back and look at the access panel on the driver side and open it up.
154764


Remove the panel and the rubber plug and push the hose through the hole and guide it over the spring coil towards the rear differential fill plug. You should have enough length so that you can fit it over the barb adapter without too much of a bend in the hose.
154765


Look for the fill plug which is on the passenger side.
154766


Once you have your hose over towards the fill plug remove the fill plug and connect the barb fitting. Finally connect the hose clamp.
154767


While you are under the car check a few places the hose can be secured down with cable ties. Sorry forgot to add that to the part list picture. I think I used 2 or 3 cable ties near the spring coil. There is a cable near which I tied it down to.

Now back to the rear of the access panel mount your breather vent. I chose to mount the breather vent inside of the car but it is up to you if you want it outside if you may think it smells.

Here is my mounting kit from spare parts I found at home.
154768


Here it is mounted to a hole already in the car:
154769


Here is the final breather valve in the back:
154770
 
Discussion starter · #3 ·
There appears to be a rubber tube in the rear differential which draws in fresh air. This is not to be confused with the breather valve on the top that exhaust hot air. More information can be found in this thread. This tube does not seem to eliminate a problem if the top breather valve stop operating which wll eventually blow the seals causing a leak.
 
#4 ·
DL175 said:
I decided to do this mod since my rear differential breather vent was rusted.

The rear differential breather valve or breather cap sits on top of the rear differential. It is pressed in and spring loaded. Hot air from the rear differential vent through this breather valve. You can check the condition of the breather valve by first jacking up your car or using ramps. I found the driver side was easier to reach over the top of the rear differential to check near the rear differential drain plug. There is very little room on the top but just enough room for your hands to feel the valve. I can feel the valve was rough and not movable. I can't see it but I am sure it was rusted. There was no road crud that I can feel. The problem with a rusted breather valve is that it could crumble if it is loosen. Another problem is that a stuck breather valve will eventually blow the seals and cause a leak in the rear differential. I decided to create a new breather valve from the fill plug.

Here is a picture of the rear differential breather valve:
View attachment 154760

Here is the parts I am going to use for my new breather mod:
  • 9 feet of rubber hose (3/8 inch) rated for oil/fuel. If you want something stronger you can use transmission hose for higher heat.
  • 2 hose clamps. I used 5/8 stainless steel hose clamps from here.
  • 1 hose barb fitting adapter. Size M18 x 1.5 to 3/8 (9.5mm) from here. Amazon sell them if you want to pay a bit more and get it quicker.
  • 1 vent valve. I got a Dorman 924-284 bought here, but there are many alternative valves you can use.
  • Hardware to mount valve. I did not buy my mounting kit. I used what spare parts I had around.
  • Cable ties
View attachment 154761

So lets get started and go to the back and look at the access panel on the driver side and open it up.
View attachment 154764

Remove the panel and the rubber plug and push the hose through the hole and guide it over the spring coil towards the rear differential fill plug. You should have enough length so that you can fit it over the barb adapter without too much of a bend in the hose.
View attachment 154765

Look for the fill plug which is on the passenger side.
View attachment 154766

Once you have your hose over towards the fill plug remove the fill plug and connect the barb fitting. Finally connect the hose clamp.
View attachment 154767

While you are under the car check a few places the hose can be secured down with cable ties. Sorry forgot to add that to the part list picture. I think I used 2 or 3 cable ties near the spring coil. There is a cable near which I tied it down to.

Now back to the rear of the access panel mount your breather vent. I chose to mount the breather vent inside of the car but it is up to you if you want it outside if you may think it smells.

Here is my mounting kit from spare parts I found at home.
View attachment 154768

Here it is mounted to a hole already in the car:
View attachment 154769

Here is the final breather valve in the back:
View attachment 154770
Click to expand...
Excellent work. I'm so happy I don't have to drop the rear to deal with a clogged vent. I already have a seal leak and the other day when I checked the oil level I heard a WHOOSH sound so I know there is a pressure problem. I have the pieces on order! THX
 
Discussion starter · #5 ·
I am glad you enjoyed my mod. So it has been two month and so far no smell or any oil coming from the breather valve. The good thing with keeping it inside is that this part will last longer and is much easier to check.
 
Discussion starter · #7 ·
For some of you wondering if there is another option to this breather valve mod and yes someone has cut a hole on top of the cargo floor for easy access. Of course it would have been cleaner if he used a hole saw and covered it with a rubber grommet. The part number for the breather valve is 90930-03235. There is no thread on this breather valve and needs to be pressed in but you can only do it if the rear differential is lowered or removed because you only have about 1.5 inch clearance. Here is the thread (post #11). So cutting the hole above the rear differential will allow you to replace the breather valve without dropping it.
 
#8 ·
DL - thanks for posting this. I had my car up on the lift last night to check it for annual inspection and service the trans, front and rear diffs.

I bought the replacement breather from Toyota, but after looking at the job and all I'd have to r&I to get the diff low enough to have room to grab the breather and pry it out, I decided to go your route and use your mod. My diff has no current leaks so I figured its not worth distributing all those components and risk damaging something in the process, when your mod accomplishes the same goal.

The only thing I think I'll do differently is I'll probably just wire tie the hose/breather to one of the wire harnesses in the lr compartment. The bracket you made is nice, but I will have to see if it's needed to properly secure the hose.

It's so far from the diff, fluid will never get up there so it shouldn't have to be vertical to work properly. I'll have to look again when I get all the parts.

Mods - this thread needs to be made a sticky.

Good stuff Sir. Much appreciated, thanks agsin.
 
#10 ·
lucathegenius said:
I am tempted to make this mod myself, but is it harmful to breathe diff air? I have 2 kids on the back of the car. Is there an alternative to go in the engine bay? (Long shot…)
Click to expand...
You raise a really good point. Perhaps it’s worth running the high breather into the top of a wheel well instead, or up to the fuel filler neck - like some people do for the nozzle of their air springs.

Engine bay will be way too far off.


2012 RAV4 Base FWD. Upgraded to large front brakes and 3rd row rear springs.

Link to SAE J2807 test description
www.caranddriver.com

That Dam Towing Test: New SAE Trailering Standards Explained

The new standards ask: Can you climb the Davis Dam grade?
www.caranddriver.com www.caranddriver.com
 
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Discussion starter · #11 ·
lucathegenius said:
I am tempted to make this mod myself, but is it harmful to breathe diff air? I have 2 kids on the back of the car. Is there an alternative to go in the engine bay? (Long shot…)
Click to expand...
My nose is very sensitive and so far I can't smell a thing inside the car which is a year now. I was just as worried about this myself but it is safe to say you will not smell anything.
 
#13 ·
DL175 said:
I decided to do this mod since my rear differential breather vent was rusted.

The rear differential breather valve or breather cap sits on top of the rear differential. It is pressed in and spring loaded. Hot air from the rear differential vent through this breather valve. You can check the condition of the breather valve by first jacking up your car or using ramps. I found the driver side was easier to reach over the top of the rear differential to check near the rear differential drain plug. There is very little room on the top but just enough room for your hands to feel the valve. I can feel the valve was rough and not movable. I can't see it but I am sure it was rusted. There was no road crud that I can feel. The problem with a rusted breather valve is that it could crumble if it is loosen. Another problem is that a stuck breather valve will eventually blow the seals and cause a leak in the rear differential. I decided to create a new breather valve from the fill plug.

Here is a picture of the rear differential breather valve:
View attachment 154760

Here is the parts I am going to use for my new breather mod:
  • 9 feet of rubber hose (3/8 inch) rated for oil/fuel. If you want something stronger you can use transmission hose for higher heat.
  • 2 hose clamps. I used 5/8 stainless steel hose clamps from here.
  • 1 hose barb fitting adapter. Size M18 x 1.5 to 3/8 (9.5mm) from here. Amazon sell them if you want to pay a bit more and get it quicker.
  • 1 vent valve. I got a Dorman 924-284 bought here, but there are many alternative valves you can use.
  • Hardware to mount valve. I did not buy my mounting kit. I used what spare parts I had around.
  • Cable ties
View attachment 154761

So lets get started and go to the back and look at the access panel on the driver side and open it up.
View attachment 154764

Remove the panel and the rubber plug and push the hose through the hole and guide it over the spring coil towards the rear differential fill plug. You should have enough length so that you can fit it over the barb adapter without too much of a bend in the hose.
View attachment 154765

Look for the fill plug which is on the passenger side.
View attachment 154766

Once you have your hose over towards the fill plug remove the fill plug and connect the barb fitting. Finally connect the hose clamp.
View attachment 154767

While you are under the car check a few places the hose can be secured down with cable ties. Sorry forgot to add that to the part list picture. I think I used 2 or 3 cable ties near the spring coil. There is a cable near which I tied it down to.

Now back to the rear of the access panel mount your breather vent. I chose to mount the breather vent inside of the car but it is up to you if you want it outside if you may think it smells.

Here is my mounting kit from spare parts I found at home.
View attachment 154768

Here it is mounted to a hole already in the car:
View attachment 154769

Here is the final breather valve in the back:
View attachment 154770
Click to expand...
How did you tighten the M18 bolt got it hand tight but cant get a wrench or socket in to tighten down
 
#15 ·
DL175 said:
I decided to do this mod since my rear differential breather vent was rusted.

The rear differential breather valve or breather cap sits on top of the rear differential. It is pressed in and spring loaded. Hot air from the rear differential vent through this breather valve. You can check the condition of the breather valve by first jacking up your car or using ramps. I found the driver side was easier to reach over the top of the rear differential to check near the rear differential drain plug. There is very little room on the top but just enough room for your hands to feel the valve. I can feel the valve was rough and not movable. I can't see it but I am sure it was rusted. There was no road crud that I can feel. The problem with a rusted breather valve is that it could crumble if it is loosen. Another problem is that a stuck breather valve will eventually blow the seals and cause a leak in the rear differential. I decided to create a new breather valve from the fill plug.

Here is a picture of the rear differential breather valve:
View attachment 154760

Here is the parts I am going to use for my new breather mod:
  • 9 feet of rubber hose (3/8 inch) rated for oil/fuel. If you want something stronger you can use transmission hose for higher heat.
  • 2 hose clamps. I used 5/8 stainless steel hose clamps from here.
  • 1 hose barb fitting adapter. Size M18 x 1.5 to 3/8 (9.5mm) from here. Amazon sell them if you want to pay a bit more and get it quicker.
  • 1 vent valve. I got a Dorman 924-284 bought here, but there are many alternative valves you can use.
  • Hardware to mount valve. I did not buy my mounting kit. I used what spare parts I had around.
  • Cable ties
View attachment 154761

So lets get started and go to the back and look at the access panel on the driver side and open it up.
View attachment 154764

Remove the panel and the rubber plug and push the hose through the hole and guide it over the spring coil towards the rear differential fill plug. You should have enough length so that you can fit it over the barb adapter without too much of a bend in the hose.
View attachment 154765

Look for the fill plug which is on the passenger side.
View attachment 154766

Once you have your hose over towards the fill plug remove the fill plug and connect the barb fitting. Finally connect the hose clamp.
View attachment 154767

While you are under the car check a few places the hose can be secured down with cable ties. Sorry forgot to add that to the part list picture. I think I used 2 or 3 cable ties near the spring coil. There is a cable near which I tied it down to.

Now back to the rear of the access panel mount your breather vent. I chose to mount the breather vent inside of the car but it is up to you if you want it outside if you may think it smells.

Here is my mounting kit from spare parts I found at home.
View attachment 154768

Here it is mounted to a hole already in the car:
View attachment 154769

Here is the final breather valve in the back:
View attachment 154770
Click to expand...
This is AWESOME!
 
#18 ·
I just got my fill plug/nipple. I am going to try to find a location for the top of the vent hose outside the car. THough I recall you saying that there is no smell, I don't want to risk it. I will be using a small filter instead of the OE type breather. From my experience with other trucks after a breather extension hose, I can smell gear oil when standing outside of the truck after a long drive.
 
Discussion starter · #19 ·
MrPulldown said:
I just got my fill plug/nipple. I am going to try to find a location for the top of the vent hose outside the car. THough I recall you saying that there is no smell, I don't want to risk it. I will be using a small filter instead of the OE type breather. From my experience with other trucks after a breather extension hose, I can smell gear oil when standing outside of the truck after a long drive.
Click to expand...
I have a very sensitive noise and I can not smell anything since I did this mod. I put the breather valve inside the access panel and the part is still clean and rust free. Where do plan on putting this on the outside of the car?
 
#20 ·
DL175 said:
I have a very sensitive noise and I can not smell anything since I did this mod. I put the breather valve inside the access panel and the part is still clean and rust free. Where do plan on putting this on the outside of the car?
Click to expand...
This is reassuring. Good to know about your nose. I have not figured out where I will mount it yet. In other vehicles I have mounted breathers in the void behind the tail light, not sure if this will work on the RAV.
 
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