Transmission pan gasket

[Jeffrey S.]

I need to replace the pan gasket on my '69 auto transmission. To make a long story short, when the drivetrain was out I had a highly recommended shop go through the trans to replace the filter, seals, etc He used a cork type gasket on the pan.. When it went back in and I filled the fluid it leaked through the gasket. He gave me a different type gasket (a dark tan fiber type). The pan is off, cleaned thoroughly, checked for staightness and I'm ready to install. I understand from reading the archives here and on other forums that no gasket sealer should be used. The Chassis Service Manual states: "Affix new gasket to bottom pan with petroleum jelly". It does not give a torque pattern for tightening the bolts. It does indicate that 12 lb. ft. is required. Anybody have any tips/advise/cautions on this? Does it matter in which order the bolts are torqued? Thank you all for your help!
Jeff

[Joe L.]

Re: Transmission pan gasket

I need to replace the pan gasket on my '69 auto transmission. To make a long story short, when the drivetrain was out I had a highly recommended shop go through the trans to replace the filter, seals, etc He used a cork type gasket on the pan.. When it went back in and I filled the fluid it leaked through the gasket. He gave me a different type gasket (a dark tan fiber type). The pan is off, cleaned thoroughly, checked for staightness and I'm ready to install. I understand from reading the archives here and on other forums that no gasket sealer should be used. The Chassis Service Manual states: "Affix new gasket to bottom pan with petroleum jelly". It does not give a torque pattern for tightening the bolts. It does indicate that 12 lb. ft. is required. Anybody have any tips/advise/cautions on this? Does it matter in which order the bolts are torqued? Thank you all for your help!
Jeff

Jeff------

The current GM gasket for your application is GM #8655625. This is a black, cellulosic fiber gasket. It is quite thin.

The very first thing you want to do is to make sure you pan is straight. If it's distorted in any way, you'll NEVER get any gasket to seal, even if you were to use sealer. Make sure ALL the bolt holes are FLAT. If not, flatten with a hammer (just like you would do for an engine oil pan).

You should not have to use any sealer (the petroleum jelly the FSM mentions is just to hold the gasket in place). However, I would not be above applying a VERY THIN coating of Permatex Ultra Black on each side of the gasket. In this case, you won't need to use any petroleum jelly and should not use any.

I would torque the attaching bolts in a "criss-cross" pattern, going through the pattern at least twice (some of the bolts will likely loosen as you tighten others).

I wouldn't start the car until the RTV had cured.

If there are any leaks noted, try slightly further tightening the bolts.

By the way, a transmission pan gasket made of rubberized cork is not a bad choice, either. I wouldn't use a conventional cork gasket but a rubberized cork (like a Victor W39341TC) will work well.

[Jeff P.]

Re: Transmission pan gasket

Jeff, Tip of the Day is; The oil pan Must be FLAT and STRAIGHT! I've used cork many times with no problems. Put the pan up to a piece of Glass and check for flatness. This is Beefy Pan and must be flat.Tighten the pan bolts with one finger on the rachet to draw the pan down evenly. I use a inch pound torque wrench in steps working across like torqueing a intake manifold. Enjoy!

[Jeffrey S.]

Re: Transmission pan gasket

Jeff and Joe- thanks for your help. I have checked the pan for flatness and it seems to be perfectly flat. On a flat steel surface (the bed of my Delta table saw) all of the ribs on the mating surface of the pan are on the steel. I have addresses the areas around the holes and they are flat.
Joe- I have a new tube of Ultra Copper. Is this the same as black except it is high heat? Is this OK to use or does the black have other properties that are more suited to this application?
Jeff

[Joe L.]

Re: Transmission pan gasket

Jeff and Joe- thanks for your help. I have checked the pan for flatness and it seems to be perfectly flat. On a flat steel surface (the bed of my Delta table saw) all of the ribs on the mating surface of the pan are on the steel. I have addresses the areas around the holes and they are flat.
Joe- I have a new tube of Ultra Copper. Is this the same as black except it is high heat? Is this OK to use or does the black have other properties that are more suited to this application?
Jeff

Jeff-----


The Ultra Copper will be fine.

[Jeffrey S.]

Re: Transmission pan gasket

Joe and Jeff,
Thanks for your help. I installed the pan with the new gasket after laying the pan on a glass bed. It appeared perfectly straight. I used a very light film of ultra copper on both sides of the gasket and torqued each bolt to 12 lb.ft. in a criss-crossed pattern and checked each after all were done. I put 4 qts. of fluid in and checked for leaks. It was dry all around. The real test will be later today when I go to the shop and check the "overnight results". I'll let you know what I find. Thanks again!
Jeff

[Jim T.]

Re: Transmission pan gasket

Still looking for leaks?

[Jeffrey S.]

Re: Transmission pan gasket

Jim,
Thanks for asking. I think I have found the culprit. I bought s new vacuum modulator and seal and installed it. There was no evidence of fluid running from the modulator seal yet the gasket was wet and dripping in the same area. I looked very carefully and noticed a small trail of fluid coming from the base of the dip stick tube. I wrapped a rag around the area and cleaned the rim of the pan. Next day no drops. So now I need to find a way to better seal this. I know that I put on a new o-ring. Any thoughts? If I loosen the bolt attaching to the engine and push down can I get the o-ring to seat better?
Jeff