I'm getting some blowby out of the trans dipstick tube on my '72 Supreme. Should there be a seal/gasket at the top of the dipstick to prevent this, and if so, would this work? I checked the ASM and couldn't find anything.
https://www.autozone.com/external-en...E&gclsrc=aw.ds

 

Check the transmission's vent tube to be sure it's not plugged. Insects like to build nests in things like that. It comes off top of the trans and points down the passenger side of it.

Also check fluid level for overfull.

There's no seal per se, just the washer under the cup at the dipstick handle. Some don't even have that.

 

I see no vent tube of which you speak, unless it's not readily visible. I have a TH400 if that matters. Also, level is good and I don't see a washer either. Would it hurt to use the grommet that I linked?

 

IMO, it's pretty difficult to get ATF blowby from the top of the transmission tube. There is a vent in the transmission itself which should vent (dump) ATF outboard if overfilled. You're sure its ATF and you're sure its coming from the top of the ATF tube?

 

You'll have to be under the car to see the transmission vent tube. Next time it's on a lift look on passenger side above the cooler lines and modulator and you should be able to see it. About a 1/8" tube, points down at an angle.

The Dorman plug you looked at would probably stop any seepage from the fill tube. Later transmissions have something like that along with an expander to push it tight against the fill tube. Concern I'd have is, if the vent is plugged, pressure would build up and start blowing fluid past seals and gaskets. Would also want to make sure it's not so tight in the tube that it won't come out with the dipstick.

Unless it's making a big mess, I'd live with it till I could check the vent tube.

 

Hey Norm, I'm pretty sure it's ATF. What I've noticed is I'm getting some "runoff" under the front passenger side floor board, and when I run my finger over it, it's got a reddish tint, so I'm guessing it's ATF, and it appears to be running down from the upper foot well area where it's slanted. I see no other leaks, and nothing I can think of would explain why it's in that area, so I just assumed it was coming out of the tube and running down.

 

Are sure your dipstick uses a top hat seal like you posted? Those were used in later years.

I'm pretty sure 1972 uses an O ring, and you'll have to remove the dipstick tube to change it. Make sure the mounting tab on the tube is tight at the bell housing bolt when you're done.

 

In that area it could be from top of dipstick, o-ring where the tube meets the transmission, or the vent tube. Could be a front seal throwing enough oil out while the car's running to sling it into that area.

 

I added some Lucas to the fluid and went out for a drive. I didn't see any residue on the aforementioned area, so hopefully the Lucas helped. As far as the o ring around the tube, I've checked that and it's dry. We'll see what happens on my trip to Ocean City this weekend.

 

The mud daubers love to plug these up.

 

Turns out I had two bolts on the trans pan that were just loose enough to let fluid seep out. Tightened them up on my way to Ocean City and all is 👍