Front Diff Actuator Breather

Looking for verification of the best way to test hoses and breather-caps for the front diff and actuator.

Looks like they are located behind the battery under the brake booster, and assuming the one in the rear (or left in this photo) is to the diff and the one in front (or right in this photo) is to the actuator.



No air should be able to be moved through the actuator hose from the end in the engine compartment (with breather-cap removed) because it is connected to a sealed electrical box basically, right? This is unlike the hose connected to the differential where air can be pulled from the engine compartment side (with breather-cap removed) while the diff fill plug is removed (otherwise the diff is sealed/vacuumed).

Checking these breathers and hoses because swapped a RH front diff Oil seal with CVs recently that leaked after install, and just redid the job with OEM seal. So wanting to chase other potential causes.

• Removed, cleaned and verified good 1 way airflow through front diff and actuator breather end caps.
• Verified air flow throw the diff breather hose from the end of the hose in the engine compartment with the filler plug removed. A-OK.
• But no air would flow through the actuator hose from the end of the hose in the engine compartment (with breather cap removed). However air flowed well through the breather cap when pushed from the hose end disconnected at the ADD.

Both seals were installed per FSM at 5.5mm +/-.3mm from axle tube end. The one removed and replaced looked fine.

Axle mating surface doesn't look scored and seems like seal was riding in the right place.



Guess I'll just trust the new seal!

 

When I installed my new ADD actuator I accidentally snapped off the little breather nipple on the plastic housing. I was so pissed off at the time of install (the new actuator didn't fix my 4WD issue) that I siliconed the broken plastic housing and plugged the hose. It's been fine for ~4k miles without issue, but none of that has been in 4WD.

Someday I will remove the plastic part of the actuator and drill and tap for a breather fitting, but so far it hasn't leaked a drop, so it's low on the priority list.

Also- that looks like a f'n clean truck. The brackets holding the breathers on mine are pretty much gone from rust.

 

That reminds me, I need to measure the OD and ID of the actuator hoses so I can find a suitable replacement. I think proactively replacing those every 10 years is probably a wise bet.

 

Looks like if you ever remove the cover need to be ready to re-clock: https://www.tundras.com/threads/4wd-diagnosis.132880/page-2#post-3429060

 

Yeah, that's one of the reasons why I'm putting it off. I clocked and re-clocked and then re-clocked some more when I dealt with all of the 4WD shit on my truck. So aggravating.

I'm so sick of 4WD issues on this truck, as soon as I save up some cash I'm sending it to the mechanic to get it straightened out.

 

Think this is the OEM top tube that comes with the breather cap but haven't look up the lower.

https://www.toyotapartsdeal.com/oem...ntial~lock~actuator~breather~41507-34021.html

Likely can just purchase vacuum line like you're planning if want to re-use the breather cap.

 

My thought is if you ever replace those breather hoses, might as well extend them all the way up to the firewall. No real need to do that with a street only truck in a dry southern state though.

 

So how do I make sure the front diff breather is functioning? Remove the caps and blow in em?

I also need to replace an axle seal for the second time.

 

This is the procedure that was performed:

Located breathers behind the battery under the brake booster (one in the rear or left in this photo is to the diff and the one in front or right in this photo is to the actuator).



Cleaned hose exteriors and pulled breathers from the two lines that terminate below the brake booster on the frame rail by the exhaust manifold.

For the breather caps:

• Sprayed brake cleaner down the end and also under the cap, articulated the cap, and sprayed with compressed air to remove any debris.
• Verified the caps spin freely and move in and out against the inner spring
• Verified one way air flow from the hose side through the cap, but not from the cap toward the hose

Also checked that the hoses didn't have holes or weren't plugged before reinstalling breather caps.

For the hose attached to the actuator:

• Verified couldn't pull air through actuator hose from the end in the engine compartment (with breather-cap removed) because it is connected to the sealed electrical box (actuator). This tested integrity of the hose (that it doesn't have a leak letting contaminants in).
• Disconnected the hose at the actuator. Verified air could flow freely through the hose (with breather-cap removed). This tested that the hose is not plugged.
• Trimmed the end of the hose where it connects to actuator after verifying there would be enough play in the hose to do so (so can reattach firmly if cracked or expanded from age).

For the hose connected to the differential:

• Verified air can't be pulled from the engine compartment side (with breather-cap removed) while the diff fill plug is installed (i.e. the diff is sealed/vacuumed). This tests integrity of the hose (that it doesn't have a leak letting contaminants in).
• After removing diff fill plug, verified air can be pulled from the engine compartment side (with breather-cap removed). This tests that the hose is not plugged.

Reinstalled diff fill plug.

Reinstalled breather caps.

 

If had oil that gathered on parts previously that could be dripping now. Do you see oil at the junction of the cv and diff or is that dry?




If the diff breather and hose is clear then when it heats up then shouldn't try to push oil past the seal.

With the driver (left) side unlike the right side, the seal just goes in till seated, so is hard to not get is straight. Did you use any sealant between the outer seal surface where it mates to the diff in case there is a scratch in the diff surface?

What does your CV axle splines and seal mating surface look like? The cv axle should be smooth and not have a groove. Should be able to see a witness mark where the seal rode on it.



The seal lip should be lubed where they mate to the cv axle. FSM calls for a new c-clip to be used, but have heard some re-use but maybe re-stretch a little.

There is a procedure with the c-clip when inserting the CV to make sure the CV inserts all the way then the clip holds the CV in the diff. Otherwise it could be coming outward and the CV sealing surface moving past the seal?

The opening of the clip is to be installed facing down. A little grease can hold it in place. Spinning the cv slightly when inserting helps line up the splines.

FSM indicates to install drive shaft to differential:

• Install new snap ring to the inboard joint shaft.
• Apply gear oil to the inboard joint shaft and differential case sliding surface.
• Set the snap ring with the opening side facing downward.
• Install the drive shaft using a brass bar and hammer.
• Whether the inboard joint shaft is in contact with the pinion shaft can't be known from the sound / feeling when driving it in.
• Check there is 2 − 3 mm (0.08 − 0.12 in.) of play in the axial (horizontal) direction.
• Check the drive shaft cannot be removed by hand.

​

 

So the CV and diff surfaces didn't appear to be scored. I reused the CV and I made sure to clean everything up. I also greased the new seal. I cleaned and reused the breather caps. I don't think the seal could go any deeper. We used a piece of PVC and a mallet. It looked and felt pretty straight. Maybe I need to replace the CV.

I'll have to pull the skid plate to see if I can find the leak, but I know it was the seal before we replaced it. I suppose it's possible it's something else now. But it was on the same side.

 

Look to see if there is a drip forming at the junction of the CV and diff or if the oil was left over from the previous leak? Maybe it's fine? Can also grab the cv and see if it feels mated and only articulates in and out 2-3mm so the clip is holding it in place.

 

It was coming out really easy vs the passenger CV that we actually replaced. So maybe it's the clip not holding it in place.

 

Check fitment for your axle but likely is this part #

Drive Shaft Snap Ring
4342504020
MSRP $2.99
Sale: $2.11

 

Valve cover gasket leaks can wet lots behind the motor including the steering rack bellows, and if bad enough, the ground. A flashlight up near the firewall and rear of the exhaust manifold might reveal a leak coming down the back of the engine.

 

Nope, VC gaskets were done a year ago. It's definitely diff oil

 

I've had a leak on the passenger side for a while. Figured I was because I nicked the seal during cv replacement. Installed a new seal, still leaks. Haven't messed with it since.

Are you saying the breather valve could have something to do with the leak?

 

Just like when people get a leaking rear axle seal and are told to make sure that breather is clear, same can happen up front. Pressure builds when things heat up, and vents out the breather. If the breather is clogged, it tries to vent somewhere else. Sometimes enough pressure builds that it pushes oil out the seals.

Axle oil seals can be tricky so there's always the possibility of install error. But it never hurts to make sure the breathers are clear. Probably ought to be part of routine maintenance whenever people change gearbox oil.

 

Can't believe I never thought of that! Makes sense.

 

Yeah this one of those things I'm actually familiar with. I've never had a seal leak because of a clogged breather, but I've definitely had older Toyota pickups where I found the breather was either completely clogged with dirt or rusted shut. Heard a hiss when I removed it.

And when I had a rear axle seal that kept leaking on my Tacoma after a wheel bearing replacement, I always had a few people post "have you cleaned the breather??". So I'm familiar...

 

It could be the breather. Also, the passenger side seal has to be set to a specific depth IIRC per FSM at 5.5mm +/-. 3mm from axle tube end or it is too far in and won't mate well to the CV so can leak.

Also found after using an aftermarket seal at the appropriate depth and then having an immediate leak afterward, that using OEM replacement, sealing outer part of seal where it mates to the diff with permatex #2 (in case the leak was coming from around outside of seal), making sure the hoses and breathers were clear, and making sure to get depth right and in straight (again) ... fixed the leak.

I think the OEM seal was really the cure as it was ever slightly different than the aftermarket. But wrote up up the procedure used to check the breathers as good measure. Hence this thread. Hope it helps you fix your leak.

 

This has been my assumption for a while. I drove it in a touch too far, but I'll make sure the breathers are clear too. Thanks!

 

Hmmm I wonder if mines in too far then?
Because there's like a 1/4" gap between the seal and the CV on driversife. Leak on my driveway is on driverside.

 

That gap between the axle and front diff is normal. I wouldn't worry. You could always tap the axle housing with a brass drift, see if it seats any further in, but I bet it's all the way in.

I don't think the driver's side has the specific tolerance that the passenger does. I replaced the driver's side seal when I did the ecgs bushing and drove it in flush (or close to), and no problems there.

I did the same with the passenger and it started leaking right away. Passenger side is probably too far in.

 

Don't think the seal can be driven in too far on the driver side as @metalpete says although supposedly it can be pounded too hard to become deformed bending the face and hence changing the seal lip. A gap of a little under 1/4" between the axle housing and the axle sounds correct because IIRC the FSM spec is <=5mm +-.3 mm when moved horizontally by hand, otherwise the axle is not considered to be fully seated and retained by the clip.

Did this only begin leaking when swapping the seal and needle bearing for the ECGS bushing, or is the CV axle new too so the oil seal mating surface on the CV axle could be a factor? You also checked the diff housing surface that the oil seal mates into for defect (can be scratched from removing the old seal), or used some sealant there?

 

I think it's the retaining clip.
So this axle and the ecgs bushing were done in 2020 IIRC.
I got regeared in 2022
The seal leaked and was redone in 2023 under warranty by the shop that did the gears l.
I just redid the seal the other day. So the CV has been removed and reinstalled a lot. I thought no it's the clip. All the surfaces looked good to me. I rubbed grease all over the seal before install.