Auto Gear Box Oil Is Disappearing

[Graham Whitehead]

I have noticed that my auto gearbox oil is creeping down and I have topped it up twice now

BUT There are no leaks under the car, drive is always as clean as a whistle, so where is it going ?

Thanks

G

 

[chadr]

Not a good sign. Have you check the radiator and coolant? There is a trans oil cooler situated in the base of the main radiator - a rad within a rad, if you like.

Check the coolant for contamination from autobox oil or vice versa.

If so, best to replace the radiator and flush and replace ALL the autobox oil after that.

Add: usually it's the auto fluid that gets contaminated by coolant ( as it's at higher pressure when up to temp). So your situation seems a little unusual.

 

[Beau]

How are you measuring the fluid? Most reliable reading done on a warm box.

 

[AdventureWagon]

If it isn't the radiator then check the transmission pan bolts are secure. I had an ATF leak a while ago down to this.

 

[StarCruiser]

As Beau says, there’s a procedure for checking the level. Engine running, warm box (do a few miles drive) cycle through all gears then dip the ATF. I would expect it to rise and contain coolant if there was a leak in the cooler in the base of the rad. There’s more pressure in the coolant system than the auto box hydraulic system at that point.

 

[clivehorridge]

It shouldn’t be too difficult to do a cooling system pressure check, that would confirm / eliminate the concept of the ATF going into the cooling system.

As said, it’s more likely that (higher pressure) coolant is being forced into the gearbox, but with little sign of mayo on the ATF dip stick, and a test that says less than 1% (I don’t know if that’s significant or not), it seems there’s an external leak, despite no drips on the driveway.

There must be an answer to this somewhere...

 

[Gav missin]

Gearbox sump gasket weeps on my 80. Doesn't drip but just mists the underside of the truck which isn't a bad thing for rust prevention . Talking about maybe a litre a year I top up.