8 3/4 spitting gear oil out of breather vent

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metalbender58

metalbender58

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I have just taken my Dart out for another test drive to break in the new rear end after swapping the 7.25 rear end for an 8.75 rear end. Everything is new, including the breather vent, except for the housing of course. Not sure what year A body the housing came from, but it had a vent on it when I bought it that was damaged. The issue I am having is there appears to be gear oil spraying out of the breather vent. I have never encountered this before. I would like to know if anyone else has had this issue. What did you determine was the cause? What was your solution?
Thank you for your time and look forward to hearing what you have to say>
 
How much? Did you check the level with it on the ground?
 
I consider it a lot when it is spraying the top of the shock and running down the housing and creating a puddle on the floor.
 
Is the vent on the tube or on the side of the hump?
 
Iirc the breathers have a valve in them, your replacement may not.

What grade oil did you use?
 
I spoke with Quick Performance and their guy said the breather vent was probably bad. It's a new vent from DR Diff. The vent cap is floppy loose, not like the one on another 8.75 rear end I have. could that be the cause?
 
The cap top should be able to move.

Did you use sealer if any type on the breather when you installed it?
 
The tube sticks down into the housing a bit MAYBE oil is spinning from the axle and hitting the threaded tube and wicking up?

If the drain was sticking it would build pressure in the housing and maybe erupt??? (but it would also tend to push past the inner seal too???)

I'm reaching for straws!

The older housings had the breather on the side of the hump, the newer ones had it on the tube, my understanding it was to reduce oil blow out. My rear has the older style breather on the side of the hump and a OEM 57 years old breather that I cleaned up. I used Teflon tape on the threads and I have not had any issues.

The FSM says some number of pints, when I drained and refilled my rear after the initial brake in period, I added the number of pints which brought the level over the bottom of the drain plug level. I assume there was a small amount of original oil left in the housing. I also recall that the level should be 1/2 inch below to at the bottom of the drain plug.
 
junkyardhero said:
is it possible that you overfilled it?
Click to expand...
IMHO the only way to overfill would be if the drivers side tire was on the ground and the pass side was raised. Then oil would fill the housing tube before coming out the filler plug hole.

@metalbender58 any chance you filled it with the housing at an angle?
 
Dana67Dart said:
IMHO the only way to overfill would be if the drivers side tire was on the ground and the pass side was raised. Then oil would fill the housing tube before coming out the filler plug hole.

@metalbender58 any chance you filled it with the housing at an angle?
Click to expand...
stranger things have happened...

i once installed a rear for a guy. he'd just dropped it off, said it was out of his other car and had lube in it, ready to go.

what he failed to mention was that he "topped it up" while it was in the back of his pickup. the outcome was about what you would expect of something with about an extra quart of lube in there.
 
Dana67Dart said:
I couldn't agree more!

And love the over fill story!
Click to expand...
or as i like to say: the tale of how to turn an afternoon project into a two day love affair that costs several hundred dollars and leaves the stink of gear oil around for weeks.
 
I was thinking that it could have been filled while on the bench or jack stands with the snout pointing downward!
 
metalbender58 said:
I spoke with Quick Performance and their guy said the breather vent was probably bad. It's a new vent from DR Diff. The vent cap is floppy loose, not like the one on another 8.75 rear end I have. could that be the cause?
Click to expand...

Yes, it could be. I had the exact same problem with an aftermarket vent. My theory is that the spring the holds to vent closed is weak in the aftermarket vents. I purchased an NOS vent on E Bay, Mopar part number 4032798, make sure it is NOS. Also, put your car on the ground, no jack stands, and remove the fill plug. Gear oil should be 1/2 to 1 inch below fill plug. Yes, thread sealant is a good idea to prevent threads leaking. Mine does not leak after I changed to NOS vent and made sure gear oil level was correct.
 
Yes, mine leaked with the new aftermarket vent tube. I thought that maybe something was sticking and building up pressure, I was having trouble with the pinion seal at the same time. I made up a pigs tail brake line tube , it works, just haven't gotten around to playing with it again. Doubt that it's overfill, as long as it isn't running out of the fill hole.
 
Dana67Dart said:
The tube sticks down into the housing a bit MAYBE oil is spinning from the axle and hitting the threaded tube and wicking up?

If the drain was sticking it would build pressure in the housing and maybe erupt??? (but it would also tend to push past the inner seal too???)

I'm reaching for straws!

The older housings had the breather on the side of the hump, the newer ones had it on the tube, my understanding it was to reduce oil blow out. My rear has the older style breather on the side of the hump and a OEM 57 years old breather that I cleaned up. I used Teflon tape on the threads and I have not had any issues.

The FSM says some number of pints, when I drained and refilled my rear after the initial brake in period, I added the number of pints which brought the level over the bottom of the drain plug level. I assume there was a small amount of original oil left in the housing. I also recall that the level should be 1/2 inch below to at the bottom of the drain plug.
Click to expand...
I just checked to see if I remembered to put teflon tape on the threads. I did not. I applied teflon tape to the threads and thought that would solve the issue. I took it for another drive and still have gear oil spraying out.
As Junkyard Hero has asked the question of the rear end being over filled. I put in the recommended 4.4 pints. The rear end was empty as I had just installed the new 3rd member. The car was on 4 jack stands on level ground.
After it happened the first time I checked the level again. I don't remember if at the time it was on jack stands or on risers. I took out the drain plug and gear lube barely trickled out the hole. If it is over filled, it can't be by much. I would think that as it blew out gear oil the level would eventually get to a point where it would slow or even stop spraying out. I could be wrong. I have been wrong before. Would it make that much difference if it were on jack stands, suspension unloaded or on risers at ride height?
I ordered a new breather vent since prevailing wisdom says the current one may be sticking and building pressure.
Thank you all for your responses. I will double check fluid level and make adjustments when I get the new breather vent installed,
 
Wonder if the gears are running hot, boiling the rear end gear lube out the vent? No Backlash between Pinion and Ring Gear?

Is the rear housing hot to the touch after your joy ride?


Had an OMC out drive that was set up too tight, the lake water was steaming off of the case cause the gears were running hot and it was hot to the touch.
Took it back to the shop and loosened up the gears and it cooled right down, ran fine the whole time I owned it after that.


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