In my “rebuild” of the transmission, I ordered a dipstick tube seal. However, I’m not sure if the right one came or how to best install the seal. 

I am wondering if anyone has replaced this seal OR found another way to seal the tube to the pan. 

Many Thanks! 


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Logan, FATSCO shows their part # is 4121-L according to their 1964- THM Catalog. 
Here is a link --> FATSCO TH400 Catalog

From memory it just pushed in to the end of the cavity. I believe I matched mine up from my universal O ring kit I bought from Summit. It is posted on my transmission project thread.

Just fyi, the original part # was 531 917 in parts Group 4.133 and was a 1 year only item:

Are you talking about where the dip stick tube goes into the oil pan?  That is a flare fitting and no seal goes there. 

Yes correct. Where the tube goes into the pan. No seal there? Then what is this o ring I got from Fatsco????? I ordered one thinking that’s where it went but didn’t look right to me lol

Isn’t that the modulator port? I’m thinking now I am getting my wires crossed haha. Does the trans dipstick tube not mount INTO the pan? 

I'm getting my words mixed tonight. There is an o-ring seal on the vacuum modulator port. I think Russ is right about where the trans dipstick filler tube attached to the transmission oil pan. I will check a couple of mine tomorrow ... am remember a compression fitting.  There is also an O-ring seal on the speedometer gear. 

Thanks! I appreciate the help. I got a new modulator and it came with an o ring, so we’re good there. 

When I placed my Fatsco order, I ordered 

2 pan gaskets

1 Filter ring

1 tube seal

front and rear seals

so there is an O ring somewhere HAHA! 

I  looked at my trans tube and there is a rubber seal up in the dipstick tube cap that twists onto the tube and it does look like it is something that can come out and be replaced but I have never thought about replacing it. you would think this would be part of the dipstick itself. Anyway, if it look like it would fit up on the dipstick cap that might be what they are referring to as the 1964 THM dipstick tube. Just guessing at this point.

Here is a picture of the inside of my THM dipstick cap. It has a seal.. still wondering if this is what they are referring to in the MPB as the 1964 THM dipstick tube seal? Logan, will the seal the sent fit up in the cap?

I’d bet that is where the seal is intended for. I will check when home.

that being said, should there NOT be a seal where the tube attaches to the pan? Or is any sealant recommended there? Want to prevent as many drips as possible 



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