G56 breather inquiry

[TRAMPLINEMAN]

I changed fluid today in my G56 and noticed the breather is leaking fluid. A little history, I’ve had the truck at two different dealers since it was new for suspicion of a leak. Neither dealer could find a leak anywhere. They just cleaned up all the fluid off the passenger side of the transmission and called it good. Today I decided to fill the transmission thru the boot like some here have suggested. When I pulled the boot off, I could immediately see that the fluid has been leaking out of the breather. Anybody have an idea why so much fluid is coming out of my breather? I understand it’s not losing quarts of fluid, but it’s losing enough to coat the entire passenger side of the transmission in 30K miles.

I decided to go with Royal Purple Synchromax in the transmission and Royal Purple Max ATF in the transfer case. I’ve never used RP before in anything, but decided to try it based off reading good reviews for years on RP. I guess I’ll find out whether it’s good or bad.

 

[seafish]

Are you sure its the breather vent it is leaking from??

I ask because the inner silicone boots are NOTORIUOS for tearing and leaking.

 

[seafish]

And also the plate that screw to the top of the transmission can loosen up...both of these cause ATF to leak from the top of the G56 inside the cab.

 

[Newsa]

And also the plate that screw to the top of the transmission can loosen up...both of these cause ATF to leak from the top of the G56 inside the cab.

The shift column on mine didn't even have the semblance of gasket. I put some liquid gasket on it

 

[MichaelOverfield]

If I had to guess, I'd say it was leaking out the breather because it was over filled and was getting hot, these G56 seem to get quite hot, to the point they make PTO cover coolers, and some have gone beyond that to keep them cool. I've not had any come out my breather, but do have the FasTCoolers for the PTO covers, which as about 2 Qts capacity, and I filled a bit above the fill hole as well.. no leaks from the breather for me, but I'm going to have to re-do the FasTCoolers as they do have seepage around the bolts.. Also I use Mobil 1 50Wt fluid, as used in other G56 Mercedes applications (with a small amount of ATF). When I re-do the FasTCoolers I'm putting on a cover with a sight glass to make it easy to verify level, with the current seepage I was concerned where the level would be, but seems to be still full when I checked via the fill plug, so it is not as yet a crisis must do and thus waits in the long queue of unfinished projects.

 

[TRAMPLINEMAN]

Are you sure its the breather vent it is leaking from??

I ask because the inner silicone boots are NOTORIUOS for tearing and leaking.

Everything on top was dry except for the breather. The breather was soaked and from there it was running down the side. My reasoning for thinking it’s the breather is because the breather is the highest point and that’s where the wetness starts.

 

[TRAMPLINEMAN]

And also the plate that screw to the top of the transmission can loosen up...both of these cause ATF to leak from the top of the G56 inside the cab.

Good point! I actually did check the plate and it was tight.

 

[TRAMPLINEMAN]

If I had to guess, I'd say it was leaking out the breather because it was over filled and was getting hot.

When I drained the factory fluid, it measured just a hair under 6 quarts, so that wouldn’t be over filled. Then I filled it with 6 quarts, so that’s not over filled. So it had 6 quarts in it both times and leaked. Most guys are filling theirs with 7 quarts and their’s aren’t leaking.

I’ll take it back apart tomorrow and see if any leaked from driving today. I cleaned it all up before driving today, so if it leaked again I should be able to tell where it’s coming from. Hopefully.

 

[Newsa]

I overfilled mine at least a quart. It is NOT a problem if it leaks from the breather vent. If it is over-filled, that is what the breather is for..

I had a little seepage due to overfilling. It has stopped

 

[seafish]

I have 8 quarts in my G56 because I also added Trans Coolers which add 1qt to capacity and then I also overfilled by 1 quart through the top of the transmission. Been running for years this way, and other then a little seepage from a spit inner boot and then another time from a loose cover plate, I have had no leaks.

 

[Newsa]

I have 8 quarts in my G56 because I also added Trans Coolers which add 1qt to capacity and then I also overfilled by 1 quart through the top of the transmission. Been running for years this way, and other then a little seepage from a spit inner boot and then another time from a loose cover plate, I have had no leaks.

I actually put 9 quarts in mine because I have the fast coolers. They hold an extra quart on each side.