If there is pressure and oil is comming out the breather, not the knuckles, then his inner axle seal may be holding. If the seals are worn then he should have oil leaking at the knuckle.
Diff breather blow-by? (1 Viewer)
- Thread starter ToyBarn
- Start date
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Kurt,
The factory breather's a one way valve. When driven, air goes out the valve due to expansion from heat in the diff housing. As it cools, the valve does not allow air in and a vaccum results which pulls hard through the axle seal as the weak spot. Drive again and the cycle repeats. This is why there is a sucking sound when you open the front diff to check the oil level. It's basically an inefficient pump that slowly pulls gear lube in from the birfs and shoves it out the breather tube.
Oil will not start coming out the knuckle until the seal is so badly worn that even the faintest pressure in the diff during the heating phase (from grease clogging the factory breather tube) pushes oil out the inner axle seal. Or the seal is completely gone and gear oil simply trickles constantly.
DougM
The factory breather's a one way valve. When driven, air goes out the valve due to expansion from heat in the diff housing. As it cools, the valve does not allow air in and a vaccum results which pulls hard through the axle seal as the weak spot. Drive again and the cycle repeats. This is why there is a sucking sound when you open the front diff to check the oil level. It's basically an inefficient pump that slowly pulls gear lube in from the birfs and shoves it out the breather tube.
Oil will not start coming out the knuckle until the seal is so badly worn that even the faintest pressure in the diff during the heating phase (from grease clogging the factory breather tube) pushes oil out the inner axle seal. Or the seal is completely gone and gear oil simply trickles constantly.
DougM
IdahoDoug,
It finally clicked for me...the OEM breathers are one-way, and the mod many of you do is two-way. Since the axles go through a heat/cool cycle, two-way breathers are required. Guess I need to add this to my list.
Thanks as always for the clear explanations.
Best Regards,
It finally clicked for me...the OEM breathers are one-way, and the mod many of you do is two-way. Since the axles go through a heat/cool cycle, two-way breathers are required. Guess I need to add this to my list.
Thanks as always for the clear explanations.
Best Regards,
Exactly. Now why didn't I think to say it that way??? The one way snorkel is a way of preventing contamination if the vehicle is immersed, but most don't drive that way and the down side is this infernal vacuum and eventual clogging. By far the better thing to do would have been to simply spend the $5 for a couple more feet of breather tube and that's what we do with this simple mod. The fuel filter on the tip is simply a cheap way to keep any grit or bugs or what have you from getting into the diff.
Doug,
When my pu was blowing oil out the breahter I had pressure in the diff.
I would remove the drain plug and it would blow out the plug.
When my rear breather was plugged on the 80 ( the breather was ok but the metal nipple on the diff that the hose goes was plugged), oil was pushed out the axle seals. I had very little grease in the bearings and it was full of oil.
If ToyBarn's had oil comming out the breather that means that the pressure was not leaking at the axle seals. If it was leakings at the axle seals, there should be oil leaking down his knuckle.
I think the problem we had was the breahter was plugged or stuck but when pressure got so high in the diff it would blow out the breahter. This means the seals were stronger than the plugged breather thus confirming that his axle seals may of been replaced when the knuckle was rebuilt.
ToyBarn, remove both front and rear breathers and stick a pipe cleaner in the nipple to see if its plugged there, if so clean it out.
With the front breather extended I can blow into it to see if its plugged.
When my pu was blowing oil out the breahter I had pressure in the diff.
I would remove the drain plug and it would blow out the plug.
When my rear breather was plugged on the 80 ( the breather was ok but the metal nipple on the diff that the hose goes was plugged), oil was pushed out the axle seals. I had very little grease in the bearings and it was full of oil.
If ToyBarn's had oil comming out the breather that means that the pressure was not leaking at the axle seals. If it was leakings at the axle seals, there should be oil leaking down his knuckle.
I think the problem we had was the breahter was plugged or stuck but when pressure got so high in the diff it would blow out the breahter. This means the seals were stronger than the plugged breather thus confirming that his axle seals may of been replaced when the knuckle was rebuilt.
ToyBarn, remove both front and rear breathers and stick a pipe cleaner in the nipple to see if its plugged there, if so clean it out.
With the front breather extended I can blow into it to see if its plugged.
landtoy80 said:
Kurt,
If oil is coming out the breather, then its volume must be replaced by something in the diff housing. That's where the grease comes in, being sucked through the inner axle seals. Pressure will NOT push oil out these seals if you have a clean vent like he does - naturally it will be vented off via the vent. My comment is that he's sucking grease into his diff again just like before the repack, so something's amiss with the inner axle seals. Absence of oil on the wheels doesn't mean the seals are in fine shape.
The point appears moot as it seems we ran out of sense of humor...
DougM
Doug, I see your pont. The seal can suck more than it could blow, if the seal is good.
If he pulls the fill plug and oil comes running out (that is if he didn't over fill it) then he may have grease getting into his diff.
My pu, somehow the oil was turning into a vapor and exiting out the breather. WHen I check the diff, it was almost empty of oil.
If he pulls the fill plug and oil comes running out (that is if he didn't over fill it) then he may have grease getting into his diff.
My pu, somehow the oil was turning into a vapor and exiting out the breather. WHen I check the diff, it was almost empty of oil.
- Thread starter
- #28
Doug,
I rebuild the front end myself and the inner seals were replaced (inside the axle tube ends). The outer seal set are on the knuckles (i.e.wipers) were replaced also. The hub seal was also replaced at this time. I'll be removing the breather and checking the diff fluid later this week. I just finished replacing an a/c evaporator coil, accumulator, o-rings and orfice tube on the Dodge diesel last weekend (total dash removal is time consuming). This weekend I finally got my bike back together; rear shock was out for a rebuild & recharge since the end of June. Needless to say the Toy is next in line for sometime this week. Keep you posted on the diff fluid level and condition later. Thanks
I rebuild the front end myself and the inner seals were replaced (inside the axle tube ends). The outer seal set are on the knuckles (i.e.wipers) were replaced also. The hub seal was also replaced at this time. I'll be removing the breather and checking the diff fluid later this week. I just finished replacing an a/c evaporator coil, accumulator, o-rings and orfice tube on the Dodge diesel last weekend (total dash removal is time consuming). This weekend I finally got my bike back together; rear shock was out for a rebuild & recharge since the end of June. Needless to say the Toy is next in line for sometime this week. Keep you posted on the diff fluid level and condition later. Thanks
Man, I don't envy you the dash removal project - what a nightmare that can be. And you don't really know how it turned out until a week later something's squeaking madly back there or you notice a whole slew of dash lights are out.
I'll be interested in what you find. If I were you, I'd do the breather mod and be done with this pressure/vacuum issue. Thanks!
DougM
I'll be interested in what you find. If I were you, I'd do the breather mod and be done with this pressure/vacuum issue. Thanks!
DougM
