Transmission pan gasket

I have not been able to source the correct pan gasket for the transmission. for my 400A. The filter is not a problem. I have already seen 4 different gasket profiles. I was surprised because I thought the TH400 case was pretty similar across the years. We tried different Chevy and GM trucks as they did not list the Ferrari 400. Does anyone have a good source for the gasket or the correct cross reference with a GM vehicle?

 

I have the aluminum pan which has a drainage plug. When I went to Carquest they had four different gasket and filter sets for the TH400. I made a template of the gasket from the original steel version. I left a template at NAPA and later today they called me back and said they had a match. Picked it up and a perfect match. For reference the NAPA part number for the pan gasket is 1-4439.

 

The NAPA gasket is rubber. Do you mean the electrical connector at the left rear of the transmission close to the oil pan? Not been able to trace the small leakage. It is not the pan. I put a boroscope up near the dipstick, but that was not it either. So I will order the o-ring and see if that resolves the problem. On the right side of the transmission, while I am at it, I will replace the modulator.

 

Great advice. Will let you know the outcome.

 

I spent hours driving around various car part places to get the right gasket, filter and O-rings. I wanted a duraprene gasket. No luck. So I was driving and I remembered Ken's comment to stop at a transmission shop. Just ahead of all places was an AAMCO shop. I told the guy I was looking for a TH400 pan gasket. He then said, "I will only sell you a duraprene gasket, all the others are not worth it and while you are at it, you should replace the o-ring for the electrical connection, the modulator and the dipstick". I then knew he was my "go to guy". Could recite rhyme and verse on every variant of the TH400. Even offered to lend me his tool for the extraction of another metal type o-ring. Will drop the pan tomorrow and see how the fluid is and if the filter is clogged.

And the best part of meeting him. He sold me the gasket, all the o-rings and charged me $5!

 

Since you will need to remove the pan to release the electrical connector, you may also want to replace the filter. Inexpensive. The filter is connected to a plastic tube that fits up into the tranny. Pull that plastic part down and you will see one 0-ring. When replacing add a second o-ring as this tube sometimes loosens and not as much fluid is picked up by the filter. The o-rings fit over the tube and not into a groove in the casing, so adding a second o-ring is not an issue.