Results of 50k on diff breather mod

[IdahoDoug]

Just under 50,000 miles ago I repacked my front axle and elevated the front diff breather to remove the one way factory valve. Today I drained and refilled all 3 diffs for the first time since.

Since the repack, the front diff has been drained and refilled 4 times, with the first three done in quick succession using premium dino to get rid of accumulated sludge from birfield grease before refilling with Mobil 1. I did all three of those within the first 10k of the repack, so for the front diff this is Mobil 1 synthetic gear oil with 40,000 miles on it.

I let the oil run 50,000 miles since I'd short changed the front a couple times and wanted to be sure to get some color contrast and was not at all worried about M1's ability to run that long. If I had changed it at my normal interval of about 30k, I was concerned there would not be much of a comparison.

Always before, the front diff was black while the rear and center were nearly clear. This contrast existed even back at 26,000 miles when the truck was young. Today, the rear and center were both nearly clear as usual, but the front was merely darker. Notably darker, but a dramatic improvement - especially since the longest interval I'm comparing this 40k on the front to was around 30k when it was always black and thick.

So, looks like the breather mod has been a resounding success in terms of not pulling birf grease through the axle seal. There is also no sign of any diff oil being pushed out the elevated breather.

DougM

 

[lovetoski]

Thanks for this post Doug. I bought all the tubing/filters/tee's/hose clamps this weekend and will do the breather mod to both my cruisers in the next few days. Great to know that you've seen a difference.

 

[LandCruiserPhil]

Just under 50,000 miles ago I repacked my front axle and elevated the front diff breather to remove the one way factory valve. Today I drained and refilled all 3 diffs for the first time since.

Since the repack, the front diff has been drained and refilled 4 times, with the first three done in quick succession using premium dino to get rid of accumulated sludge from birfield grease before refilling with Mobil 1. I did all three of those within the first 10k of the repack, so for the front diff this is Mobil 1 synthetic gear oil with 40,000 miles on it.

I let the oil run 50,000 miles since I'd short changed the front a couple times and wanted to be sure to get some color contrast and was not at all worried about M1's ability to run that long. If I had changed it at my normal interval of about 30k, I was concerned there would not be much of a comparison.

Always before, the front diff was black while the rear and center were nearly clear. This contrast existed even back at 26,000 miles when the truck was young. Today, the rear and center were both nearly clear as usual, but the front was merely darker. Notably darker, but a dramatic improvement - especially since the longest interval I'm comparing this 40k on the front to was around 30k when it was always black and thick.

So, looks like the breather mod has been a resounding success in terms of not pulling birf grease through the axle seal. There is also no sign of any diff oil being pushed out the elevated breather.

DougM

Good info to know Doug
A couple of questions - What breather filter/s did you use and what kind of service if any?

 

[tucker74]

Just under 50,000 miles ago I repacked my front axle and elevated the front diff breather to remove the one way factory valve.

What did you actually do - just extend the breather ... or remove a valve?

Tucker

 

[erics_bruisers]

I think the success lies within opening up the breather, not necessarily extending it, under normal driving conditions -- I think that's what you're saying anyways --

-- what he attained by opening the breather was that the diff now sucks air in from the breather, not the birfs, which results in sucking grease in to the diff --

eric

 

[concretejungle]

Good info to know Doug
A couple of questions - What breather filter/s did you use and what kind of service if any?

i'm curious about the filter also. I extended the front up into the engine compartment, but when i went to NAPA to get a filter, the guys at the parts counter said that i needed a special filter they didn't sell?

 

[scottm]

I found several filters with multiple hose fittings, should work. They're somewhere in my garage I think, yeah I should get that done.

 

[Rookie2]

I found several filters with multiple hose fittings, should work. They're somewhere in my garage I think, yeah I should get that done.

Why the need for a filter? Per Beo's write-up, the rear diff. breather cap is modified and used to cap off the singly converged line in the engine compartment.

Thanks,
Rookie2

 

[concretejungle]

i found my front cap at least (haven't extended the rear until i have the front finished, then i'll just T into it) was no longer functioning properly.

 

[scottm]

I just thought the filter was cheap and might keep dust out. I worked on a Pathfinder, every gearbox had steel lines up to the top of the firewall then bent down to keep water out.

 

[lovetoski]

In the writeup on doing this mod, most refer to using a fuel filter.

 

[landtoy80]

M1 is 75w90 and the diff calls for 80w90.
The M1 75w90 flows like water. My gear oil 80w90 (both syn and dino) flows like warm honey.
Is it good for the diff's to run the lighter oil?

 

[concretejungle]

if someone could post a pic of this cheap fuel filter, i'd appreciate it. That way i could take that to NAPA and tell them this is what i want.

 

[tucker74]

if someone could post a pic of this cheap fuel filter, i'd appreciate it. That way i could take that to NAPA and tell them this is what i want.

The ones I've seen have been just cheapo in-line filters ... you should be able to find them on the shelf.

Tucker

 

[Cruiserdrew]

if someone could post a pic of this cheap fuel filter, i'd appreciate it. That way i could take that to NAPA and tell them this is what i want.

No pic needed. Get some cheap plastic fuel filters at PepBoys with a 1/4 input. They work great.

 

[IdahoDoug]

I simply removed the existing rubber tube and its flapper and took off the bracket that holds it to the frame partway up and the clamp that held it on the axle nipple before tossing the old tube in the trash. Then I used 1/4 inch rubber fuel line (unaffected by oils, etc) to replace it. Simply feed it down from the battery tray area, then go under and put the bracket and clamp around it before sliding it onto the nipple. Reattach the bracket (leave room for suspension movement like the original tube) and position the clamp. Then go back up above and choose where you want to cut off the length. Pop the filter on the tip, and zip tie the hose to something near the battery tray.

The filter I used was a $2 inline fuel filter available at any auto parts store. It's simply a tubular semi opaque offwhite plastic affair with the filter media plainly visible that has a 1/4" nipple on each end. you stuff one end in the tube and the other end's open to the atmosphere. Now, whenever the diff needs to breath (twice each time you driv it, actually) it won't pull any grit in. Frankly the filter's kinda overkill but it was a couple bucks and makes me feel good. Maintenance is zero since the filter only filters perhaps a couple teaspoons each time and will likely never plug at that rate.

I'm very interested in the possible decrease in birf maintenance however. With no cross contamination between the birfield chamber and differential chamber I guess it will be up to my nerve as to how long I think the birf's grease is holding up. Since I used synthetic Amsoil it could be a very long time indeed unless I take it in the water.

The previous limiter was when the grease around the birf was sucked out by the differential chamber vacuum. Unfortunately when the diff did suck grease in, the birf is the first to go as it's right next to the axle seal into which the grease is sucked, losing its grease first. Then, when the old breather tube got plugged with grease and began to cause pressure that forced diff oil back through the seal, guess who's on the front line and suffers first? Our old friend the birf again. So this may prove to be quite an improvement in birfield maintenance.

DougM

 

[RavenTai]

if someone could post a pic of this cheap fuel filter, i'd appreciate it. That way i could take that to NAPA and tell them this is what i want.

As Doug said the flow rate is minimal, low/0 pressure, it was unfiltered before so any filter no matter how coarse is an improvement, pretty easy specs for any filter to fill, I got this one because I can see easily in it, I think I got it at AutoZone

(Chevy rear diff relocated to near brake MC)

Doing this to the 80 was on "the list" this thread bumped it up quite a bit, at least getting rid of the vacuum flapper now, relocation can wait till later

 

[concretejungle]

Thanks guys. I was actually looking at that filter on the shelf at NAPA, but decided to wait until i got some advice here.

Thanks again, looks like i'll be stopping by NAPA after work today.

 

[Rookie2]

Since I used synthetic Amsoil it could be a very long time indeed unless I take it in the water.

Why's that? I thought that was one of the main reasons for the mod. If the vacuum has been eliminated, where would the water be getting in from?

Are you guys using clear tubing link Raven's Chevy, or staying with low pressure fuel line?

Thanks,
Rookie2

 

[RavenTai]

Why's that?Are you guys using clear tubing link Raven's Chevy, or staying with low pressure fuel line?

That is not standard clear tubing, it is industrial pneumatic line used on welding fixtures, much tougher than the vinyl fish tank line you get at home depot and alike,

¼” fuel line seams to be a favorite for this app and sounds good to me, parker has some very nice abrasion resistant line for apps like this if you have a parker store nearby