4L80E Transmission Leak

[chris_maxwell]

My transmission is leaking out of the vent tube; what causes this, the cooler line or? I had the tranny shop put on a larger pan on the truck and since then is when I noticed it.

It may be leaking from other areas as well. In four days it went down at least 3 pints. It has not thrown any codes and the drivability seems good when the level is correct.

I have gotten poor mileage since the transmission was updated a couple of years ago and the heads were replaced; about 10-12 miles per gallon.


i put this in the members forum which wasn't probable the correct place to post.

[KenDavis]

If it's your filler tube, I just had my filler tube repaired. My local shop said it was common in these engines. To replace the filler tube you have to drop the transmission. I had two leaks, one where it slides into the transmission and the other near the mounting bracket higher up. If you back up a hill you'll lose fluid like crazy. Hope this helps.

[chris_maxwell]

I just bought a new tube because either the tranny shop or the place who finished my head job did a repair where the bracket that mounts to the heads; they over lapped it and used a hose clamp. So I wasn’t convinced that the level is accurate. Funny that it only started a week ago, about 2 weeks after putting on the extra capacity pan.

I am fairly certain that there is fluid coming out the vent hose as it is wet inside.

So you think you have to pull the tranny to install the tube?

Thanks for your response Ken.

[suburbanK-2500HD]

Hi

You dont have to drop the tranny.
i fixed mine after a broken fixplate. i didnt drop the tranny.
Just clean the area where the tube enters the tranny first.

:)

[rameye]

my tranny shop did the same thing,,,when they drop the tranny to work on it...the dip tube bracket remains hung on the bell housing stud.....its a hard to see what the hold up is ...soo the weight of dropping trans peels the bracket quite nicely from the dip tube leaving a hole to deal with....voila!

[rustyk]

Also check the vent tube - I didn't have a leak, but the tube was collapsed.

[chris_maxwell]

Rusty,

What problems did it cause you with the collapsed vent tube? Can I blow air through it to see if it is plugged; or how would I clear a plug with the tranny in?

Rameye,

Were you losing lots of fluid from the dip stick tube? I wouldn’t think that it would have broke just doing a pan change out; although he did say he had to do something to the cross support..... I will have to try and get a light and a mirror up in there once it stops raining.

Thanks All!! And A Happy New Year To You :)

[rameye]

if he moved that tranny in any way with the cross member removed...it could stress the bracket and start to tear the tube.

this will result in a leak thats fairly high up the tube...but it will weep fluid. depending on the angle of incline...it could be a significant amount.

the situation in my opinion will not cause fluid to blow out under pressure however....its more of a weepy drippy leak in a normal tranny.