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Topic: Rear Axle Vent (Read 1840 times) previous topic - next topic

Rear Axle Vent

Hellooo,
I did not see any threads named "Rear Axle Vent" in a quick search, so here goes.  This is a problem with another late 80s Ford.  After battling with a rear seal leak for most of the time I have had the vehicle, I have come to the conclusion the axle vent must be blocked.  The vent is a little mushroom type cap, twice the size at least, and appearing as one of those tire valve caps.  It has a sideways wiggle to it when I toy with it.  I am curious whether there is a way to check this mechanism without (oops) breaking it off or something to that effect.  If it wiggles, I am presuming it is NOT a twist off cap.  It does not leak.  When I open the diff check screw/plug there is a pressure of air (whether pos or neg I am not sure) situation, leading me to suspect this is what causes the leak.  ????

JR

Rear Axle Vent

Reply #2 –
What i do is remove the vent and install a short length of rubber hose to it. Extend it  up in to the body and secure it to the body. Then go to your nearest JEEP Dealer and order a new vent valve!!! If you have any pressure or VACUUM of any kind the vent is plugged. And that is NG!!!
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Rear Axle Vent

Reply #3 –
Good idea


I used an fittings ran a peice of hose and I mini k&n breather

Rear Axle Vent

Reply #4 –
Good idea


I used an fittings ran a peice of hose and I mini k&n breather

Rear Axle Vent

Reply #5 –
Thanks so much for the prompt input.  Now the question is ---how do you open/remove the vent---turn the cap??  I have never looked at it closely other than to know it's fairly flimsy to play with---jiggly.  I did not see any base on it, but never really looked.  I'm sure it is plugged.  Too bad I did not realize it long ago.   

John R

Rear Axle Vent

Reply #6 –
We remove the cap and use the remaining part of the fitting for the hose. Be careful you can break them . They are strong but not that strong!!!
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Rear Axle Vent

Reply #7 –
OK Tom, I see what you mean.  I started this job hours back because I have no clue how much fluid may have sneaked out on me at the diff case--I couldn't imagine much---and had to get this job started today.  Incidentally, this situation results from a leak at the diff case and it must be my fault in not securing it well after the bearing seal job--not sure on that.  The diff was fine for weeks after.  I wasn't going to drive the car again until this leak is fixed.  As far as the vent is concerned, I used a deep socket and took the whole unit off and allowed me to figure out how it works.  The cap floats on a relaxed spring.  When up, it allows air to escape.  When down, it is closed ??--and this presumes that submersion in water closes the valve cap by compression or such?  The spring doesn't have much tension and I see how the cap could get stuck open or closed.  I couldn't tell whether this one was bad except it was sluggish.  I soaked it in carb cleaner and blew it out with air----it appears acceptable so I reinstalled it.  It was not difficult to remove (surprised!), but the big deal is to avoid getting crud down the hole.  10 years ago a shop opened the diff case and reinstalled the cover without a gasket.  I should have bought a gasket when I did the work because I did not used the gobs of silicone they used in securing it.  I literally had to pry the edge of the cover with a flat bladed putty knife and hammer to get it off.

Rear Axle Vent

Reply #8 –
Yes the vent is spring loaded and has a disc valve. I use the JEEP valve because they work so well. BUT!!! They do not seal completely unless it gets clogged. That is one reason JEEP and most all 4X4 have the valve mounted high in the chassis. They use a long hose with the valve mounted very high on the vehicle. So once you have fixed or modified the valve or replaced it with a PLASTIC one you are good to GO!!! Now to all the SILICONE JUNKIES!!!!! We normally never use it unless there is no gasket available for the thing you are trying to seal. The stuff is great but extremely limited in the automotive applications. Always use a gasket glued to the cover with HIGH TACH and coat the other side with some light grease. I do this on non street driven cars. Burt it works on them also. This way you can remove the cover and not rip the gasket. Now i only do this in an emergency like at the TRACK. But every time i remove a gasket i replace it with a new one. Other than reusable gaskets that are showing up on modern cars. Thanks

NOTE gaskets in my view should be installed DRY. Other than a very slight amount of GOO to hold it from moving. If it cant move install it DRY!!! On 99% of the rear covers i install they are completely DRY and a good gasket used !!!

By the way the vent is one of the most overlooked device bar none on a car. And having it working properly is a MUST!!!

You found out the hard way what a clogged vent can do. And i do not run in to people that actually know it is there and how it works. It is totally ignored and it has to be clean and operational. You handled it QUITE WELL and found out exactly what it does and how it works. SILLY LITTLE PERDOINGER that can play havoc on the final drive. Good JOB!!!
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!

Rear Axle Vent

Reply #9 –
You should know that almost everything that has come with a rear diff in the last 10 years has had the cover sealed with oil resistant RTV.  Not everyone seems to be able to restrain themselves from globbing on as much as they can fit, though.  As an example, the workshop manual for an 05 Mustang calls for a 2mm bead around the cover. This is done by a machine at assembly, but takes a steady hand and a caulk gun in the field.  On the flipside, Accurate Engines, a local reman outfit near me, puts high temp, low tensile RTV on absolutely everything and it's disgusting.  They use the orange junk that expands on contact with oil and then dissolves in it.  We get so much of their  that they deny warranty on, and we find it everyplace: O-rings, rubber front cover seals, 5.4L intakes, everywhere, and as much as it takes to make it out the door not leaking.

Rear Axle Vent

Reply #10 –
I've never used a gasket on the 8.8's in my cars.  Always a very thin layer of RTV, let it sit for about ten minutes, and bolt up the cover.  The difference is I have T/A covers on both my cars so they torque down way better than the tin stamped units from the factory.

All I can say is thank you for a great thread!  I am going to check the breather on my Mustang as I have not cleaned that  thing in a couple of years.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

Rear Axle Vent

Reply #11 –
Thanks for the comments guys.  The Ford diff cover is hard plastic and you really have to scrub it with a flat ser to release some of the adhesive. I also used a single edge blade---and then you have to work along the raised edge to get it all off. On Thursday (tomorrow), I will clean it up with brake cleaner and so clean the case edge and put all together. Today I bought the gasket and another tube of black gasket maker (the tube I used last month was old stuff).  I am all confused now as to using any adhesive, but will likely use a light surface of it on the gasket.  Tom, I feel like you would have to twist my arm to make me install it dry!!! Dunno why?

All of the jobs I have done involving gaskets--water pumps/thermostats, etc, --have not had a sealant problem, so I was surprised this one failed (and I had done the diff 15 years ago with no issues). ...So the reasoning that maybe excessive internal case pressure was pushing the oil out at a weak spot.

As far as making the job tight, the secret to me has always been to make sure the surfaces are CLEAN! As far as this job is concerned, I just hope I solved the seal leak problem on the RR wheel. Another thought --the book calls for 3.8 pints of oil in the case. This amount does not bring the level to the filler hole (contrary to my 1970s education that the level should be at the hole), so I wonder if there is such a thing as overfilling the diff and causing a seal leak at the wheel end. Whew....too much on this subject I know!

Rear Axle Vent

Reply #12 –
Actually many diffs call for specific amounts of fluid. Chevy says the DANA should be 1/8 inch below the fill plug. But the same axle in a DODGE calls for a slight drip from the hole and it is FULL. I fill just about all diffs  to the bottom of the fill mark and allow it to seep out then it is full. But in the 1 ton axles you need to OVER FILL them so i install a RISER That i came up with to raise the level of the fluid and allow an extra QUART!! On those units you will burn out the axle bearings in a flash if you dont do this. As far as using SILICONE on a gasket it is not something i would do. the gasket makers feel the same. Never use a gasket along with SILICONE. If you are hell bent on using sealer use SUPER WEATHER STRIP ADHESIVE. Using SILICONE and a gasket is totally wrong and can make the gasket LEAK!! If you want to use SILICONE use it and do not use the gasket. But do not use both together. Reason being the gasket guys say it does two things. It makes the gasket move and it does not stick to the gasket . This makes a very POOR sealing situation!! Good luck.
I spend money I don't have, To build  cars I don't need, To impress people I don't know

HAVE YOU DRIVEN A FORD LATELY!!
 

Rear Axle Vent

Reply #13 –
OK--the job was finished earlier this afternoon.  I tacked the gasket to the cover, and (Tom don't read this part), I put an itsy-bitsy bead of gasket maker along the raised lip on the cover which fits into the case.  We'll see how this goes, but I'm leaving the Towncar in the garage for the weekend.  For Friday, I'm taking the '88 Thunderbird to work.  It has a coolant leak which has been spooky.  Sometimes it leaks and sometimes it doesn't--I think its the timing cover. I also applied for Social Security this week, so I wonder how much longer I can screw-up DIY jobs!!  My 93 year old aunt just suffered a major stroke yesterday (found out today) and I hope to be as healthy as she was at 90
....if I could even live that long. 

JR