trans gasket?

ttwinsupra said:

HI, I know this sounds like a simple question but seem like everyone has a different answer! when I was in automotive school they told us NOT to use both a regular gasket and silicone... but when I worked as a mechanic for a lil after school my boss actually told me TO USE BOTH RTV and a gasket, he told me it was an old mechanic thing and RTV is better now and both will make sure it seals even with imperfections... on google there's various different answers, all the way to RTV + gasket will cause the gasket to slip out and actually cause leaks.... so I would like to hear from you G-body guys and get your take on it, since ill be doing it on a g-body...

so im about to change the gasket and filter on my trans, it game with a RUBBER gasket, I have some good RED RTV... im planing on putting a thiiiiiiin layer of RTV on the pan side ONLY, to help hold the gasket and maybe seal up some imperfections in the pan.... is that a good idea? should I just scrap the RTV and just use the rubber gasket? or should I use more? put a thin layer on the trans side too?

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yep everyone's different, I'd use rtv to tack a cork gasket to a surface(s) just to keep it in place for assembly but i don't see it holding onto those silicone rubber ones well.the thing about trans pan gaskets failing is people have a tendency to over torque those thin metal pans and it distort's it.just my.02.with a steel pan i'd use the cork and any rtv to assist.the thing with rtv is to not just tighten it down rite away as that'll just push it all out.put it on and hand tighten it all,let it set up for about an hour that way it's congealed when you fully tighten it making it a thicker seal.

I don't like using RTV on transmission gaskets because today's fluid can break it down a bit over time. It led to my pan seeping from a thick cork gasket, and it had seen very little road time but sat for years. If any pieces of RTV should fall into the pan they can easily clog the delicate passageways of the transmission if they sneak past the filter. This is most likely to happen AFTER replacing the sealed gasket for the first time, as scraping the silicone can send slivers of it all over the valve body and soaking with brake cleaner is no guarantee that you don't shoot them up into a hole.

Unless needing the "squish" I've come to like the Farpak Fiber gaskets more than cork but am in love with the reusable blue silicone units- they're glorious. If you're going to use sealer, maybe only apply it to the pan side to avoid having to scrape the trans rails and slinging debris onto the valve body. When using a silicone gasket then no sealant is used at all and this is not an issue.

Another trick that I've had great success with is spraying the gasket with something like 3M adhesive or even just hair spray. It works well but only if the surfaces are squeaky clean, and cleanup is a breeze with a scraper (with Farpak, not always with cork). Unlike removing RTV which is a pain every time for me.

The cheap, thin rubber gaskets suck donkey balls and commonly leak. They're absolute garbage: For God's sake throw it away. If a transmission gasket requires sealant it's a shitty gasket.

Any kind of plain gasket for a trans pan I use Hylomar blue sealant

565bbchevy said:

Any kind of plain gasket for a trans pan I use Holymar sealant

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Personal experiences have shaped us differently, that's all. Hylomar is an excellent sealant and works to plug all sorts of low pressure leaks, and holds gaskets in place like a champ- my grandfather was a fan of it and used it often. I like that it doesn't harden and cleans with alcohol, making it better for valve covers than Indian Head or Gasgacinch. My belief is that the trans and pan should be so incredibly flat that one could theoretically use the Hylomar alone, but I choose gaskets alone. Just a preference.

On my 200R4 in my Regal with a deep cast aluminum pan I only used this Mr. Gasket pan gasket and no issues after 5 years.

Back when my car had an automatic I used some good ol' miltary surplus GAA (Grease, Artillery & Automotive) to hold the gasket to the pan. Thick & held it in place so it could be remounted. No hazard to the transmission if a little got inside.

Way back when, I built auto transmissions and we just used cork gaskets. I can’t ever recall a comeback with a pan leak.
Most times on factory pans, they seemed to get overtightened over the years. This causes the metal to hump up at the bolt holes.
Simply put the pan rail on the edge of a steel table and lightly hammer the “ bumps” flat. Look at most used pans and you will see the elevated spots at the holes.

timo22

Unless it’s the thick rubber solid core gasket I think silicone is needed with a stock pan.