Transmission leaking, need help to diagnose , overnight,

[hooverfish]

Trans leaking, seems to be only dripping from the flywheel dust cover.

I drained the pan a couple weeks ago and put in 2.5 quarts fresh fluid
which is amount that I took out. And now it's leaking, about an ounce overnight.

Cannot see any leaks around speedo, dipstick, etc. It's all coming from bottom of dust cover.

This is a 75,000 mile truck (72 350/350) and the trans shifts/drives perfect.

I searched a lot of old threads but couldn't find this exact problem. Any suggestions or ideas appreciated.

[Hammond68]

Front seal.

[weim55]

Leaks can be tricky and elusive to find the source. For the automatic transmissions in our trucks the number one source for an overnight leak is the dipstick tube O-ring. As the truck sits overnight the level in the transmission pan rises up past the level of that O-ring. Not uncommon for that leak to make its way to the transmission torque converter cover and drip to the floor from there. While your leak could certainly be the torque converter seal it’s not nearly as common. As simple and cheap as that dipstick O-ring seal is to replace I would do that first and see if that cures the problem. If it doesn’t I would pull the transmission and just do a complete re-seal of all the external seals and be done with it.

Steve weim55 Colorado

[WorkinLonghorn]

weim55 beat me to it. Good post. We used to see loads of front seal leaks and these usually leak pretty badly while on the rack engine running. If this is it, obviously it needs to come out for a reseal job minimum. If it's got 75K on it I would seriously consider a "rebuild".

[jocko]

I'd have to agree that's most likely source. One thing to elminate is to look at your trans cooler lines and see if one is perhaps cracked or a fitting loose. Depending where the issue is, it "could" cause it to look like drips from the pan/tc cover (I had a trans line coupler in my trans cooling line almost even with the dust cover and some of the fluid was leaking onto the dust cover and running down to the center, making it appear to be coming from inside the dust cover at first glance). Just a thought, highly unlikely if your trans cooler lines are untouched from original config though, unless there is a pinhole/small crack etc. Anyway, recommend just look at them, but they are not likely the problem, unfortunately.

[RodnRudy]

Get it up on jack stands and remove the dust cover. Then clean everything with brake cleaner and run it in gear for a while, shut it off and wait for the leak to appear. Like others have said, ATF can track to the front of the trans even though it is seeping out some where else.

[Wrenchbender Ret]

Check around the selector shaft. The seal in there is a very common leak.
I would look & watch very closely before I snatched the trans out.

[hooverfish]

I really appreciate all the replies. I'm going to wait a couple days and see what I can find. Check out all the suggestions. I will post an update when I know something. Hate this because I'm sure I did it with the trans fluid, self inflicted, I should know better.

[Grumpy old man]

Fastest easiest way to find any oil/ trans fluid leak .


https://www.youtube.com/watch?v=2wCtBVlkujE

[hooverfish]

My neighbor told me about a transmission expert so I took it to him. Nicest guy you'd ever want to meet, 76 years old, been rebuilding transmissions since 1967, still works every day in his one bay garage. He confirmed it was the front seal, pulled the transmission, and recommended complete overhaul while I had it out. Said he was surprised it even pulled in reverse due to condition of a pump or something. And showed me the seals and O-rings that were all hard as rocks, filter and pan full of the coating stuff from clutches.

He did a great job, cleaned the trans case in this oven type device, all new parts, seals, guaranteed, etc. He treated it like he owned it, did all the little stuff, cleaning and such. I'm convinced he could rebuild one of these blindfolded. Charged me $850 which I think is very good.


Thanks again to everyone for your help and comments.

[jocko]

Great news. And great price. I used to have a friend like that, who was really a friend of my Dad's - so he treated me like family, when I was a kid. He had a racing trans shop and was always happy to lend a hand - usually out of his own small home garage with the double 55-gal drum wood stove for those cold NW Indiana winters AFTER his long work days, and usually for free. In fact, I seem to recall he just "gave" me a rear end for my 57 chev when I did stupid kid stuff and destroyed my spider gears... (but was at least able to drive home in reverse late, very late at night...) I learned a lot from him, most of which had nothing to do with cars and trucks. Those folks are still around, just not as plentiful. And I'd imagine many of "those" folks reside on this board

[hooverfish]

Originally Posted by jocko

Great news. And great price. I used to have a friend like that, who was really a friend of my Dad's - so he treated me like family, when I was a kid. He had a racing trans shop and was always happy to lend a hand - usually out of his own small home garage with the double 55-gal drum wood stove for those cold NW Indiana winters AFTER his long work days, and usually for free. In fact, I seem to recall he just "gave" me a rear end for my 57 chev when I did stupid kid stuff and destroyed my spider gears... (but was at least able to drive home in reverse late, very late at night...) I learned a lot from him, most of which had nothing to do with cars and trucks. Those folks are still around, just not as plentiful. And I'd imagine many of "those" folks reside on this board

Thank you for sharing those memories. Those old fellas are local treasures.

[Barnfind46]

I agree with Jocko, I think a lot of those guys are on here in our little community!