[1969GiPper]

Sorry if this has been asked before. What “brand” of transmission pan gasket seals the best? Transmission is a 1969 Turbo 400 and the pan gasket seems to always be leaking/seeping. Also do you use the gasket “as is” or do you coat it with gasket sealer or RTV? If sealer or RTV is used do you let it “set up” somewhat before installing? How long before you fill with fluid? Do you put sealer on the bolt threads? Any special tightening sequence? Basically want to know your secrets.

Thank you in advance.

[72LuxuryLeMansLa.]

Originally Posted by 1969GiPper

Sorry if this has been asked before. What “brand” of transmission pan gasket seals the best? Transmission is a 1969 Turbo 400 and the pan gasket seems to always be leaking/seeping. Also do you use the gasket “as is” or do you coat it with gasket sealer or RTV? If sealer or RTV is used do you let it “set up” somewhat before installing? How long before you fill with fluid? Do you put sealer on the bolt threads? Any special tightening sequence? Basically want to know your secrets.

Thank you in advance.

I'm no expert but have done a few pan gaskets in my life. #1 is to make sure the pan is straight! People OVER TORQUE PANS AND VALVE COVERS! When they over-torque they distort the sheet metal at the bolt holes.
Secondly, ensure all old gasket material/adhesive/rtv/ whatever is removed prior to installing new Fel pro gasket with no rtv/adhesive/whatever. The only way I would use anything on the gasket is in a vertical application where you need to hold the gasket in place to get the bolts started.

[69camarox]

check the linkage seal it leaks down onto the edge of the pan gasket and runs around the gasket making it look like a pan leak when it is not

[72LuxuryLeMansLa.]

I forgot about the tightening sequence! With sheet metal I always start in the center and work out. You can choose, clockwise or counter..... Whatever floats your boat.

[Schurkey]

PIck a gasket. It's not that critical. I've used many different kinds, and all the "name brands" work fine. Heck, my employer used to buy 25-packs of bulk gaskets, and even they worked OK. As said, the pan needs to be flat at the bolt holes except that old-time pans often had a sealing ridge embossed into the metal between the bolt holes.

Install the gasket CLEAN and DRY. NO gasket sealer.

Originally Posted by 69camarox

check the linkage seal it leaks down onto the edge of the pan gasket and runs around the gasket making it look like a pan leak when it is not

Yup, gravity and wind will move the ATF all around. Lots of "pan gasket leaks" have nothing to do with the pan gasket.

I've fixed a bunch of "pan gasket leaks" by
re-sealing the manual shaft, (any trans, but TH350 seem to be the most popular)
re-sealing the modulator valve,
re-sealing the torque converter, (verify the position of the converter bushing in the pump--Fords were especially bad at having the bushing shift which blocks the drainback hole.)
re-sealing the dipstick tube (after replacing the tube because it's cracked at the O-ring groove.)
re-sealing the speedo drive gear and/or housing (sometimes have to replace the driven gear due to groove worn in the plastic by the seal.)

Other sources are the kickdown cable/TV cable on a TH350 or TH700, and the O-ring around the electrical connector on a TH400.

[stevep]

Make sure the the connector on the driver's side isn't leaking.

[Half-Inch Stud]

I use petroleum jelly on all -O-rings for seal. Never use RTV on them O-rings.

Pan sealing : how did GM ever get so many TH400 cars out without leaking?

[PunchT37]

Install the gasket CLEAN and DRY. NO gasket sealer.

Amen.

[SRR]

Lay the pan on something confirmed flat and take a good look at it. Since they have no drain plug a lot of guys let them hang to drain and IMHO this bends them. With all that said I usually replace mine with aluminum ones with drain plugs and more capacity.

[taff2]

If it's a chrome oil pan then you need to scuff the flange surface with wet and dry paper, otherwise it will weep. Dress flat the flange especially around the bolt holes, any gasket is fine-I always use cork as it conforms well, pan rail on the trans and oil pan MUST be dry and oil free, then put a thin bead of Grey Abro or Permatex around the oil pan flange ONLY and nip up all the bolts lightly. Then go around all the bolts 3 or 4 times using a ratchet bar held by the head not the shaft-use your weakest hand and you won't over tighten the gasket. I use this procedure on every trans I build and haven't had any complaints of leaking and I build around 70-100 a year.

[Sun Tuned]

I saw back a year or so ago where in the new products section of a hot rod or similar magazine....
FelPro was bringing to market a blue steel core turbo 400 gasket. Much like the newer one piece steel core engine oil pan gaskets. With the blue silicone outer jacket.

Anyone know if that happened??

I haven't had time to follow up on this.

[Sun Tuned]

Moroso 710-93103 from jegs looks close.

Agree with the pan checks above for sure no matter what gasket gets used.