Differential fluid leak

[gr_diver]

My mechanic when topping up the differential fluid, he opens the plug towards the rear of the car, and fills it until the fluid is level with the hole. He then lets any excess drain and then tightens the plug. Is this the correct method?

I am asking because everytime he tops it up, there is fluid leak when I park the car from the differential's breather-valve for a few days, then it stops. Now that summer approaches I notice that it started dripping a bit sometimes, but just a dab. Maybe the extra heat is responsible. But why is it dripping anyway? Could it be a faulty breather valve? Or just excess fluid? Is his procedure correct?

Thanks in advance!

[greensmurf20]

that seems to be the general accepted way, and the way i also do it on my own cars, same with manual transmissions. not sure why your rear axle would keep pushing fluid out through the vent cap tho, its not making complete sense.

[mblackprowler]

Sounds like you need a new rear. I have one with only 30,000 miles on it ! Check ad posted this site

[jeff denton]

When he tops it off, how much lube is he adding, and is it leaking anywhere else also?
I vented my axle more like how it is done on off road equipment, by tapping the vent hole to 1/8" pipe, screwing in a nipple, and running a 5/16 hose up thru the floor, up as high as possible and securing it at shelf level.
It hasn't dripped a drop yet.
This would work on any differential or gearbox of any kind, pretty common on real hard working equipment especially those running in dirty and wet environments.
On Speedway GT the vent was moved from the right side to the left side simply because the right tube is sealed way in next to the carrier bearing, that way all the oil isn't pulled into the tube by the G-forces of constant hard left turns, thus the vent on the right side would not be working.
Venting is important, when one gets plugged up the pressure builds up and you'll have a seal leak for sure!

[greensmurf20]

mblackprowler:

your rear axle wont fit into gr_drivers car. he's in greece and shipping would be much more expensive than rebuilding his, as he has a 78' opel, theres no way it can be a GT, and therefore wont work since GT axles are GT specific.

[baz]

Sounds like you need a new rear. I have one with only 30,000 miles on it ! Check ad posted this site

had a look and can not find your ad where did you post it ?

[jordan]

Can fancy synthetic differential oil be used? if so what weight?

[aknassassin]

Is it possible to clean the vent hole with the little wire in it? Is it worth drilling and tapping the axle housing on the left side just to have second vent for street use, i'd hate to have a vent not work and blow a seal if I can prevent it.

[gr_diver]

no it does not leak anywhere else (e.g. from gaskets), just "discharges" the an amount from the valve, and then stops leaking. It hadn't leaked since October when it was last topped-up, until now that temperature rised about 15 celcius, and will stop again in a few days (stabilize in summer temperature -> new oil volume), and will not leak until topped-up again... Since it leaks from the valve, I can say for sure that the valve isn't plugged with dust-road debris...

[baz]

it must be just a little too full when topped up and sorts itself out when you drive

[kwilford]

what is the car on when he checks the fluid level? Is the car level? Maybe it is "tipped" forward such that it takes a bit more fluid than it should if it were level, and spits the excess out the vent?

[jeff denton]

By all means use synthetic gear lube whenever possible! The truck manufacturers insist on it, there must be something to it...
As for venting, were you to "hose it" as I described your problem is solved, trust me!

[RallyBob]

As for venting, were you to "hose it" as I described your problem is solved, trust me!

Jeff's right, we always ran hoses from our rear differential and transmission vents into an overflow can, since under racing duress and summer heat we always had a little bit of 'puking' of fluids from the vents.

Bob

[gr_diver]

He raises the car on the kind of machine that has four "arms", which are placed under the cars jacking points. Which means that the whole car is raised, not just an axle. He does it this way, so while the engine oil is draining he tops-up the gearbox, the rear axle, inspects fuel lines, brake lines, wheel bearings etc.

So I don't think that the chassis is not level. I will check out what viscosity he is using, maybe it is wrong, so under the heat the expansion might cause the discharge...

By the way, that vent valve, does it have any mechanical parts or is it just a tube with notches on the end's sides that leave the excess pressure discharge through the cap?

[Turbo X]

your putting to much oil in it... have him check the oil with his little finger and bend at first knuckle, the oil should be at his finger nail, thats about a 1/2 in low... thats anough until the next inspection... the gearing is picking up to much oil and its spitting it out the breather tube.. as long as he can touch the oil it is fine..